Solved: The air in an insulated, rigid compressed-air tank

Problem 1P When is the flow through a control volume steady?

Problem 2P Define mass and volume flow rates. How are they related to each other?

Problem 207P Air is to be heated steadily by an 8-kW electric resistance heater as it flows through an insulated duct. If the air enters at 50°C at a rate of 2 kg/s, the exit temperature of air is (a) 46.0°C ________________ (b) 50.0°C ________________ (c) 54.0°C ________________ (d) 55.4°C ________________ (e) 58.0°C

Problem 4P Consider a device with one inlet and one outlet. If the volume flow rates at the inlet and at the outlet are the same, is the flow through this device necessarily steady? Why?

Problem 3P Does the amount of mass entering a control volume have to be equal to the amount of mass leaving during an unsteady-flow process?

Air whose density is \(0.078 \mathrm{lbm} / \mathrm{ft}^{3}\) enters the duct of an air-conditioning system at a volume flow rate of \(450 \mathrm{ft}^{3} / \mathrm{min}\). If the diameter of the duct is \(10 \mathrm{in}\), determine the velocity of the air at the duct inlet and the mass flow rate of air. Equation Transcription: Text Transcription: 0.078 lbm/ft^3 450 ft^3/min

Air enters a 28-cm diameter pipe steadily at \(200 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) with a velocity of \(5 \mathrm{~m} / \mathrm{s}\). Air is heated as it flows, and leaves the pipe at \(180 \mathrm{kPa}\) and \(40^{\circ} \mathrm{C}\). Determine \((a)\) the volume flow rate of air at the inlet, \((b)\) the mass flow rate of air, and \((c)\) the velocity and volume flow rate at the exit. Equation Transcription: 20°C 40°C Text Transcription: 28-cm 200 kPa 20 degree celsius 5 m/s 180 kPa 40 degree celsius

Problem 5P The ventilating fan of the bathroom of a building has a volume flow rate of 30 L/s and runs continuously. If the density of air inside is 1.20 kg/m3, determine the mass of air vented out in one day.

Problem 8P A steady-flow compressor is used to compress helium from 15 psia and 70°F at the inlet to 200 psia and 600°F at the outlet. The outlet area and velocity are 0.01 ft2 and 100 ft/s, respectively, and the inlet velocity is 50 ft/s. Determine the mass flow rate and the inlet area.

Problem 9P A 2-m3 rigid tank initially contains air whose density is 1.18 kg/m3. The tank is connected to a high-pressure supply line through a valve. The valve is opened, and air is allowed to enter the tank until the density in the tank rises to 5.30 kg/m3.Determine the mass of air that has entered the tank.

A cyclone separator like that in Fig. P5–10 is used to remove fine solid particles, such as fly ash, that are suspended in a gas stream. In the flue-gas system of an electrical power plant, the weight fraction of fly ash in the exhaust gases is approximately \(0.001\). Determine the mass flow rates at the two outlets (flue gas and fly ash) when \(10\ kg/s\) of flue gas and ash mixture enters this unit. Also determine the amount of fly ash collected per year. Equation Transcription: Text Transcription: 0.001 10 kg/s

A spherical hot-air balloon is initially filled with air at \(120 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) with an initial diameter of \(5 \mathrm{~m}\). Air enters this balloon at \(120 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) with a velocity of \(3 \mathrm{~m} / \mathrm{s}\) through a \(1-\mathrm{m}\) diameter opening. How many minutes will it take to inflate this balloon to a 15 -m diameter when the pressure and temperature of the air in the balloon remain the same as the air entering the balloon? Equation Transcription: 20°C Text Transcription: 120 kPa 20 degree celsius 3 m/s

A pump increases the water pressure from \(100 \mathrm{kPa}\) at the inlet to \(900 \mathrm{kPa}\) at the outlet. Water enters this pump at \(15^{\circ} \mathrm{C}\) through a \(1-\mathrm{cm}\)-diameter opening and exits through a 1.5-cm-diameter opening. Determine the velocity of the water at the inlet and outlet when the mass flow rate through the pump is \(0.5 \mathrm{~kg} / \mathrm{s}\). Will these velocities change significantly if the inlet temperature is raised to \(40^{\circ} \mathrm{C}\) ? Equation Transcription: 15°C 40°C Text Transcription: 100 kPa 900 kPa 15 degree celsius 0.5 kg/s 40 degree celsius

Problem 14P Refrigerant-134a enters a 28-cm diameter pipe steadily at 200 kPa and 20°C with a velocity of 5 m/s. The refrigerant gains heat as it flows and leaves the pipe at 180 kPa and 40°C. Determine (a) the volume flow rate of the refrigerant at the inlet, (b) the mass flow rate of the refrigerant, and (c) the velocity and volume flow rate at the exit.

A desktop computer is to be cooled by a fan whose flow rate is \(0.34 \mathrm{~m}^{3} / \mathrm{min}\). Determine the mass flow rate of air through the fan at an elevation of \(3400 \mathrm{~m}\) where the air density is \(0.7 \mathrm{~kg} / \mathrm{m}^{3}\). Also, if the average velocity of air is not to exceed \(110 \mathrm{~m} / \mathrm{min}\), determine the diameter of the casing of the fan. Equation Transcription: Text Transcription: 0.34 m^3/min 0.7 kg/m^3 110 m/min

Consider a 300-L storage tank of a solar water heating system initially filled with warm water at \(45^{\circ} \mathrm{C}\). Warm water is withdrawn from the tank through a \(2-\mathrm{cm}\) diameter hose at an average velocity of \(0.5 \mathrm{~m} / \mathrm{s}\) while cold water enters the tank at \(20^{\circ} \mathrm{C}\) at a rate of \(15 \mathrm{~L} / \mathrm{min}\). Determine the amount of water in the tank after a 20-minute period. Assume the pressure in the tank remains constant at 1 atm. Equation Transcription: 45°C 20°C Text Transcription: 300-L 45 degree celsius 2-cm 20 degree celsius 15 L/min 1 atm

A smoking lounge is to accommodate 15 heavy smokers. The minimum fresh air requirement for smoking lounges is specified to be \(30\ L/s\) per person (ASHRAE, Standard 62, 1989). Determine the minimum required flow rate of fresh air that needs to be supplied to the lounge, and the diameter of the duct if the air velocity is not to exceed \(8\ m/s\). Equation Transcription: Text Transcription: 30 L/s 8 m/s

Problem 18P How do the energies of a flowing fluid and a fluid at rest compare? Name the specific forms of energy associated with each case.

A house is maintained at 1 atm and \(24^{\circ} \mathrm{C}\), and warm air inside a house is forced to leave the house at a rate of \(150 \mathrm{~m}^{3} / \mathrm{h}\) as a result of outdoor air at \(5^{\circ} \mathrm{C}\) infiltrating into the house through the cracks. Determine the rate of net energy loss of the house due to mass transfer. Equation Transcription: 24°C 5°C Text Transcription: 24 degree celsius 150 m^3/h 5 degree celsius

Problem 17P What is flow energy? Do fluids at rest possess any flow energy?

Problem 20P A water pump increases the water pressure from 15 psia to 80 psia. Determine the flow work, in Btu/lbm, required by the pump.

Problem 22P Steam is leaving a pressure cooker whose operating pressure is 20 psia. It is observed that the amount of liquid in the cooker has decreased by 0.6 gal in 45 minutes after the steady operating conditions are established, and the cross-sectional area of the exit opening is 0.15 in2. Determine (a) the mass flow rate of the steam and the exit velocity, (b) the total and flow energies of the steam per unit mass, and (c) the rate at which energy is leaving the cooker by steam.

Problem 23P A diffuser is an adiabatic device that decreases the kinetic energy of the fluid by slowing it down. What happens to this lost kinetic energy?

Problem 21P Refrigerant-134a enters the compressor of a refrigeration system as saturated vapor at 0.14 MPa, and leaves as superheated vapor at 0.8 MPa and 60°C at a rate of 0.06 kg/s. Determine the rates of energy transfers by mass into and out of the compressor. Assume the kinetic and potential energies to be negligible.

Problem 25P Is heat transfer to or from the fluid desirable as it flows through a nozzle? How will heat transfer affect the fluid velocity at the nozzle exit?

Problem 24P The kinetic energy of a fluid increases as it is accelerated in an adiabatic nozzle. Where does this energy come from?

Problem 27P The stators in a gas turbine are designed to increase the kinetic energy of the gas passing through them adiabatically. Air enters a set of these nozzles at 300 psia and 700°F with a velocity of 80 ft/s and exits at 250 psia and 645°F. Calculate the velocity at the exit of the nozzles.

Air enters a nozzle steadily at \(50 \mathrm{psia}, 140^{\circ} \mathrm{F}\), and \(150 \mathrm{ft} / \mathrm{s}\) and leaves at \(14.7 \mathrm{psia}\) and \(900 \mathrm{ft} / \mathrm{s}\). The heat loss from the nozzle is estimated to be \(6.5\) Btw/bm of air flowing. The inlet area of the nozzle is \(0.1 \mathrm{ft}^{2}\). Determine \((a)\) the exit temperature of air and \((b)\) the exit area of the nozzle. Equation Transcription: 140°F Text Transcription: 140 degree fahrenheit 900 ft/s 6.5 Btu/lbm 0.1 ft2

Problem 33P Carbon dioxide enters an adiabatic nozzle steadily at 1 MPa and 500°C with a mass flow rate of 6000 kg/h and leaves at 100 kPa and 450 m/s. The inlet area of the nozzle is 40 cm2. Determine (a) the inlet velocity and (b) the exit temperature.

The diffuser in a jet engine is designed to decrease the kinetic energy of the air entering the engine compressor without any work or heat interactions. Calculate the velocity at the exit of a diffuser when air at \(100 \mathrm{kPa}\) and \(30^{\circ} \mathrm{C}\) enters it with a velocity of \(350 \mathrm{~m} / \mathrm{s}\) and the exit state is \(200 \mathrm{kPa}\) and \(90^{\circ} \mathrm{C}\). Equation Transcription: 30°C 90°C Text Transcription: 100 kPa 30 degree celsius 200 kPa 90 degree celsius

Problem 29P Air at 600 kPa and 500 K enters an adiabatic nozzle that has an inlet-to-exit area ratio of 2:1 with a velocity of 120 m/s and leaves with a velocity of 380 m/s. Determine (a) the exit temperature and (b) the exit pressure of the air.

Steam enters a nozzle at \(400^{\circ} \mathrm{C}\) and \(800 \mathrm{kPa}\) with a velocity of \(10 \mathrm{~m} / \mathrm{s}\), and leaves at \(300^{\circ} \mathrm{C}\) and \(200 \mathrm{kPa}\) while losing heat at a rate of \(25 \mathrm{~kW}\). For an inlet area of \(800 \mathrm{~cm}^{2}\), determine the velocity and the volume flow rate of the steam at the nozzle exit. Equation Transcription: 400°C 300°C Text Transcription: 400 degree celsius 800 kPa 10 m/s 300 degree celsius 200 kPa 25 kW 800 cm^2

Steam at \(3 \mathrm{MPa}\) and \(400^{\circ} \mathrm{C}\) enters an adiabatic nozzle steadily with a velocity of \(40 \mathrm{~m} / \mathrm{s}\) and leaves at \(2.5 \mathrm{MPa}\) and \(300 \mathrm{~m} / \mathrm{s}\). Determine \((a)\) the exit temperature and \((b)\) the ratio of the inlet to exit area \(A_{1} / A_{2}\). . Equation Transcription: Text Transcription: 3 MPa 400 degree celsius 2.5MPa 300 m/s A_1/A_2

Air at \(13 \mathrm{psia}\) and \(65^{\circ} \mathrm{F}\) enters an adiabatic diffuser steadily with a velocity of \(750 \mathrm{ft} / \mathrm{s}\) and leaves with a low velocity at a pressure of \(14.5 \mathrm{psia}\). The exit area of the diffuser is 3 times the inlet area. Determine (a) the exit temperature and (b) the exit velocity of the air. Equation Transcription: 65°F Text Transcription: 65 degree fahrenheit 750 ft/s

Problem 37P Refrigerant-134a enters a diffuser steadily as saturated vapor at 600 kPa with a velocity of 160 m/s, and it leaves at 700 kPa and 40°C. The refrigerant is gaining heat at a rate of 2 kJ/s as it passes through the diffuser. If the exit area is 80 percent greater than the inlet area, determine (a) the exit velocity and (b) the mass flow rate of the refrigerant.

Problem 35P Nitrogen gas at 60 kPa and 7°C enters an adiabatic diffuser steadily with a velocity of 275 m/s and leaves at 85 kPa and 27 °C. Determine (a) the exit velocity of the nitrogen and (b) the ratio of the intel to exit area A1/A2

Problem 34P Refrigerant-134a at 700 kPa and 120°C enters an adiabatic nozzle steadily with a velocity of 20m/s and leaves at 400 kPa and 30°C. Determine (a) the exit velocity and (b) the ratio of the inlet to exit area A1/A2.

Problem 40P Consider an air compressor operating steadily. How would you compare the volume flow rates of the air at the compressor inlet and exit?

Problem 38P Steam at 4 MPa and 400°C enters a nozzle steadily with a velocity of 60 m/s, and it leave's at 2 MPa and 300°C. The inlet area of the nozzle is 50 cm2, and heat is being lostat a rate of 75 kJ/s. Determine (a) the mass flow rate of the steam, (b) the exit velocity of the steam, and (c) the exit area Hg of the nozzle.

Air at \(80 \mathrm{kPa}, 27^{\circ} \mathrm{C}\), and \(220 \mathrm{~m} / \mathrm{s}\) enters a diffincer at a rate of \(2.5 \mathrm{~kg} / \mathrm{s}\) and leaves at \(42^{\circ} \mathrm{C}\). The exit area of the diffuser is \(400 \mathrm{~cm}^{2}\). The air is estimated to lose heat at a rate of \(18 \mathrm{~kJ} / \mathrm{s}\) during this process. Determine (a) the exit velocity and (b) the exit pressure of the air. Equation Transcription: Text Transcription: 80 kPa,27 degree celsius 2.5 kg/s 42 degree celsius 400 cm^2 18 kJ/s

Problem 41P Will the temperature of air rise as it is compressed by an adiabatic compressor? Why?

Problem 43P Air flows steadily through an adiabatic turbine, entering at 150 psia, 900°F, and 350 ft/s and leaving at 20 psia, 300°F, and 700 ft/s. The inlet area of the turbine is 0.1 ft2. Determine (a) the mass flow rate of the air and (b) the power output of the turbine.

Problem 42P Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold air leaving the turbine into the house. From a thermodynamic point of view, is the proposed system sound?

Problem 44P Refrigerant-134a enters an adiabatic compressor as saturated vapor at -24°C and leaves at 0.8 MPa and 60°C. The mass flow rate of the refrigerant is 1.2 kg/s. Determine (a) the power input to the compressor and (b) the volume flow rate of the refrigerant at the compressor inlet.

Problem 45P Refrigerant-134a enters a compressor at 180 kPa as a saturated vapor with a flow rate of 0.35 m3/min and leaves at 700 kPa. The power supplied to the refrigerant during compression process is 2.35 kW. What is the temperature of R-134a at the exit of the compressor?

5-46 Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are \(4 \mathrm{MPa}, 500^{\circ} \mathrm{C}\), and \(80 \mathrm{~m} / \mathrm{s}\), and the exit conditions are \(30 \mathrm{kPa}, 92\) percent quality, and \(50 \mathrm{~m} / \mathrm{s}). The mass flow rate of the steam is \(12 \mathrm{~kg} / \mathrm{s}\). Determine \((a)\) the change in kinetic energy, \((b)\) the power output, and \((c)\) the turbine inlet area. Equation Transcription: Text Transcription: 4 MPa,500 degree celsius 80 m/s 30kPa,92 50 m/s 12 kg/s

Problem 48P Steam enters an adiabatic turbine at 10 MPa and 500°C and leaves at 10 kPa with a quality of 90 percent. Neglecting the changes in kinetic and potential energies, determine the mass flow rate required for a power output of 5 MW.

Problem 49P Steam flows steadily through a turbine at a rate of 45,000 lbm/h, entering at 1000 psia and 900°F and leaving at 5 psia as saturated vapor. If the power generated by the turbine is 4 MW, determine the rate of heat loss from the steam.

Helium is to be compressed from \(105 \mathrm{kPa}\) and \(295 \mathrm{~K}\) to \(700 \mathrm{kPa}\) and \(460 \mathrm{~K}\). A heat loss of \(15 \mathrm{~kJ} / \mathrm{kg}\) occurs during the compression process. Neglecting kinetic energy changes, determine the power input required for a mass flow rate of \(60 \mathrm{~kg} / \mathrm{min}\). Equation Transcription: Text Transcription: 105 kPa 295 K 700 kPa 460 K 15 kJ/kg 60 kg/min

Problem 51P Carbon dioxide enters an adiabatic compressor at 100 kPa and 300 K at a rate of 0.5 kg/s and leaves at 600 kPa and 450 K. Neglecting kinetic energy changes, determine (a) the volume flow rate of the carbon dioxide at the compressor inlet and (b) the power input to the compressor.

Problem 51P Air is compressed from 14.7 psia and 60°F to a pressure of 150 psia while being cooled at a rate of 10 Btu/lbm by circulating water through the compressor casing. The volume flow rate of the air at the inlet conditions is 5000 ft3/min, and the power input to the compressor is 700 hp. Determine (a) the mass flow rate of the air and (b) the temperature at the compressor exit.

Problem 54P An adiabatic gas turbine expands air at 1300 kPa and 500°C to 100 kPa and 127°C. Air enters the turbine through a 0.2-m2 opening with an average velocity of 40 m/s, and exhausts through a 1-m2 opening. Determine the mass flow rate of air through the turbine and (b) the power produced by the turbine.

Steam enters a steady-flow turbine with a mass flow rate of \(13 \mathrm{~kg} / \mathrm{s}\) at \(600^{\circ} \mathrm{C}, 8 \mathrm{MPa}\), and a negligible velocity. The steam expands in the turbine to a saturated vapor at \(300 \mathrm{kPa}\) where 10 percent of the steam is removed for some other use. The remainder of the steam continues to expand to the turbine exit where the pressure is \(10 \mathrm{kPa}\) and quality is 85 percent. If the turbine is adiabatic, determine the rate of work done by the steam during this process. Equation Transcription: Text Transcription: 13 kg/s 600 degree celsius,8MPa 300 kPa 10 kPa

Steam flows steadily into a turbine with a mass flow rate of \(26 \mathrm{~kg} / \mathrm{s}\) and a negligible velocity at \(6 \mathrm{MPa}\) and \(600^{\circ} \mathrm{C}\). The steam leaves the turbine at \90.5 \mathrm{MPa}\) and \(200^{\circ} \mathrm{C}\) with a velocity of \(180 \mathrm{~m} / \mathrm{s}\). The rate of work done by the steam in the turbine is measured to be \(20 \mathrm{MW}\). If the elevation change between the turbine inlet and exit is negligible, determine the rate of heat transfer associated with this process. Equation Transcription: 600°C 200°C Text Transcription: 26 kg/s 6 MPa 600 degree celsius 0.5 MPa 200 degree celsius 180 m/s 20 MW

Problem 57P Air enters the compressor of a gas-turbine plant at ambient conditions of 100 kPa and 25°C with a low velocity and exits at 1 MPa and 347°C with a velocity of 90 m/s. The compressor is cooled at a rate of 1500 kJ/min, and the power input to the compressor is 250 kW. Determine the mass flow rate of air through the compressor.

Problem 58P Why are throttling devices commonly used in refrigeration and air-conditioning applications?

Problem 59P Would you expect the temperature of air to drop as it undergoes a steady-flow throttling process? Explain.

Problem 60P Would you expect the temperature of a liquid to change as it is throttled? Explain.

Problem 61P During a throttling process, the temperature of a fluid drops from 30 to ?20°C. Can this process occur adiabatically?

Refrigerant-\(134a\) is throttled from the saturated liquid state at \(700 \mathrm{kPa}\) to a pressure of \(160 \mathrm{kPa}\). Determine the temperature drop during this process and the final specific volume of the refrigerant. Equation Transcription: Text Transcription: 134a 700 kPa 160 kPa

Saturated liquid-vapor mixture of water, called wet steam, in a steam line at \(1500 \mathrm{kPa}\) is throttled to \(50 \mathrm{kPa}\) and \(100^{\circ} \mathrm{C}\). What is the quality in the steam line? Equation Transcription: 100°C Text Transcription: 1500 kPa 50 kPa 100 degree celsius

Refrigerant-\(134a\) at \(800 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) is throttled to a temperature of \(-20^{\circ} \mathrm{C}\). Determine the pressure and the internal energy of the refrigerant at the final state. Equation Transcription: 25°C ?20°C Text Transcription: 134a 800 kPa 25 degree celsius ?20 degree celsius

Reconsider Prob. 5–65. Using EES (or other) software, investigate the effect of the exit pressure of steam on the exit temperature after throttling. Let the exit pressure vary from 6 to \(1 \mathrm{MPa}\). Plot the exit temperature of steam against the exit pressure, and discuss the results. Equation Transcription: Text Transcription: 1 MPa

Problem 67P Refrigerant-134a enters the expansion valve of a refrigeration system at 120 psia as a saturated liquid and leaves at 20 psia. Determine the temperature and internal energy changes across the valve.

Problem 68P Consider a steady-flow mixing process. Under what conditions will the energy transported into the control volume by the incoming streams be equal to the energy transported out of it by the outgoing stream?

Problem 69P Consider a steady-flow heat exchanger involving two different fluid streams. Under what conditions will the amount of heat lost by one fluid be equal to the amount of heat gained by the other?

Problem 70P When two fluid streams are mixed in a mixing chamber, can the mixture temperature be lower than the temperature of both streams? Explain.

Problem 65P A well-insulated valve is used to throttle steam from 8 MPa and 350°C to 2 MPa. Determine the final temperature of the steam.

Problem 71P Liquid water at 300 kPa and 20°C is heated in a chamber by mixing it with superheated steam at 300 kPa and 300°C. Cold water enters the chamber at a rate of 1.8 kg/s. If the mixture leaves the mixing chamber at 60°C, determine the mass flow rate of the superheated steam required.

Reconsider Prob. 5–74. Using EES (or other) software, investigate the effect of the mass flow rate of the cold stream of \(R-134a\) on the temperature and the quality of the exit stream. Let the ratio of the mass flow rate of the cold stream to that of the hot stream vary from 1 to 4. Plot the mixture temperature and quality against the cold-to-hot mass flow rate ratio, and discuss the results. Equation Transcription: Text Transcription: R-134a

Problem 74P A stream of refrigerant-134a at 1 MPa and 20°C is mixed with another stream at 1 MPa and 80°C. If the mass flow rate of the cold stream is twice that of the hot one, determine the temperature and the quality of the exit stream.

Problem 73P Water at 65°F and 20 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. If both streams enter the mixing chamber at the same mass flow rate, determine the temperature and the quality of the exiting stream.

Problem 77P Steam is to be condensed on the shell side of a heat exchanger at 75°F. Cooling water enters the tubes at 50°F at a rate of 45 lbm/s and leaves at 65°F. Assuming the heat exchanger to be well-insulated, determine the rate of heat transfer in the heat exchanger and the rate of condensation of the steam.

A heat exchanger is to heat water \(\left(c_{p}=4.18 \mathrm{~kJ} / \mathrm{kg}{ }^{\circ} \mathrm{C}\right)\) from 25 to \(60^{\circ} \mathrm{C}\) at a rate of \(0.2 \mathrm{~kg} / \mathrm{s}\). The heating is to be accomplished by geothermal water \(\left(c_{p}=4.31 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)\) available at \(140^{\circ} \mathrm{C}\) at a mass flow rate of \(0.3 \mathrm{~kg} / \mathrm{s}\). Determine the rate of heat transfer in the heat exchanger and the exit temperature of geothermal water. Equation Transcription: Text Transcription: (c_p=4.18 kJ/kg dot degree celsius) 60 degree celsius 0.2 kg/s c_p=4.31 kJ/kg dot degree celsius 140 degree celsius 0.3 kg/s

In steam power plants, open feedwater heaters are frequently utilized to heat the feedwater by mixing it with steam bled off the turbine at some intermediate stage. Consider an open feedwater heater that operates at a pressure of \(1000 \mathrm{kPa}\). Feedwater at \(50^{\circ} \mathrm{C}\) and \(1000 \mathrm{kPa}\) is to be heated with superheated steam at \(200^{\circ} \mathrm{C}\) and \(1000 \mathrm{kPa}\). In an ideal feedwater heater, the mixture leaves the heater as saturated liquid at the feedwater pressure. Determine the ratio of the mass flow rates of the feedwater and the superheated vapor for this case. Equation Transcription: 50°C 200°C Text Transcription: 1000 kPa 50 degree celsius 200 degree celsius

A thin-walled double-pipe counter-flow heat exchanger is used to cool oil \(\left(c_{p}=2.20 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)\) from \(150 \mathrm{to} 40^{\circ} \mathrm{C}\) at a rate of \(2 \mathrm{~kg} / \mathrm{s}\) by water \(\left(c_{p}=4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)\) that enters at \(22^{\circ} \mathrm{C}\) at a rate of \(1.5 \mathrm{~kg} / \mathrm{s}\). Determine the rate of heat transfer in the heat exchanger and the exit temperature of water. Equation Transcription: Text Transcription: (c_p=2.20 kJ/kg dot degree celsius) 40 degree celsius (c_p=4.18 kJ/kg dot degree celsius) 2 kg/s 22 degree celsius 1.5 kg/s

Problem 80P In a steam heating system, air is heated by being passed over some tubes through which steam flows steadily. Steam enters the heat exchanger at 30 psia and 400°F at a rate of 15 lbm/min and leaves at 25 psia and 212°F. Air enters at 14.7 psia and 80°F and leaves at 130°F. Determine the volume flow rate of air at the inlet.

Air \(\left(c_{p}=1.005 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)\) is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. Air enters the heat exchanger at \(95 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) at a rate of \(0.6 \mathrm{~m}^{3} / \mathrm{s}\). The combustion gases \(\left(c_{p}=\right.\) \(1.10 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) ) enter at \(160^{\circ} \mathrm{C}\) at a rate of \(0.95 \mathrm{~kg} / \mathrm{s}\) and leave at \(95^{\circ} \mathrm{C}\). Determine the rate of heat transfer to the air and its outlet temperature. Equation Transcription: Text Transcription: (c_p=1.005 kJ/kg dot degree celsius) 95 kPa 20 degree celsius 0.6 m3/s (c_p=1.10 kJ/kg dot degree celsius) 160 degree celsius 0.95 kg/s 95 degree celsius

An air-conditioning system involves the mixing of cold air and warm outdoor air before the mixture is routed to the conditioned room in steady operation. Cold air enters the mixing chamber at \(7^{\circ} \mathrm{C}\) and \(105 \mathrm{kPa}\) at a rate of \(0.55 \mathrm{~m}^{3} / \mathrm{s}\) while warm air enters at \(34^{\circ} \mathrm{C}\) and \(105 \mathrm{kPa}\). The air leaves the room at \(24^{\circ} \mathrm{C}\). The ratio of the mass flow rates of the hot to cold air streams is \(1.6\). Using variable specific heats, determine (a) the mixture temperature at the inlet of the room and (b) the rate of heat gain of the room. Equation Transcription: 7°C 34°C 24°C Text Transcription: 7 degree celsius 105 kPa 34 degree celsius 24 degree celsius

Problem 82P Air enters the evaporator section of a window air conditioner at 14.7 psia and 90°F with a volume flow rate of 200 ft3/min. Refrigerant-134a at 20 psia with a quality of 30 percent enters the evaporator at a rate of 4 lbm/min and leaves as saturated vapor at the same pressure. Determine (a) the exit temperature of the air and (b) the rate of heat transfer from the air.

Hot exhaust gases of an internal combustion engine are to be used to produce saturated water vapor at \(2 \mathrm{MPa}\) pressure. The exhaust gases enter the heat exchanger at \(400^{\circ} \mathrm{C}\) at a rate of \(32 \mathrm{~kg} / \mathrm{min}\) while water enters at \(15^{\circ} \mathrm{C}\). The heat exchanger is not well insulated, and it is estimated that 10 percent of heat given up by the exhaust gases is lost to the surroundings. If the mass flow rate of the exhaust gases is 15 times that of the water, determine (a) the temperature of the exhaust gases at the heat exchanger exit and (b) the rate of heat transfer to the water. Use the constant specific heat properties of air for the exhaust gases. Equation Transcription: 400°C 15°C Text Transcription: 2 MPa 400 degree celsius 32 kg/min 15 degree celsius

The evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at \(200 \mathrm{kPa}\) with a quality of 22 percent and a flow rate of \(2.65 \mathrm{~L} / \mathrm{h} . \mathrm{R}-22\) leaves the evaporator at the same pressure superheated by \(5^{\circ} \mathrm{C}\). The refrigerant is evaporated by absorbing heat from air whose flow rate is \(0.75 \mathrm{~kg} / \mathrm{s}\). Determine (a) the rate of heat absorbed from the air and (b) the temperature change of air. The properties of R-22 at the inlet and exit of the condenser are \(h_{1}=220.2 \mathrm{~kJ} / \mathrm{kg}, v_{1}=0.0253 \mathrm{~m}^{3} / \mathrm{kg}\), and \(h_{2}=398.0 \mathrm{~kJ} / \mathrm{kg}\). Equation Transcription: Text Transcription: 200 kPa 2.65 L/h 5 degree celsius 0.75 kg/s h_1=220.2 kJ/kg,v_1=0.0253 m^3/kg h_2=398.0 kJ/kg

Refrigerant-134a at \(1 \mathrm{MPa}\) and \(90^{\circ} \mathrm{C}\) is to be cooled to \(1 \mathrm{MPa}\) and \(30^{\circ} \mathrm{C}\) in a condenser by air. The air enters at \(100 \mathrm{kPa}\) and \(27^{\circ} \mathrm{C}\) with a volume flow rate of \(600 \mathrm{~m}^{3} / \mathrm{min}\) and leaves at \(95 \mathrm{kPa}\) and \(60^{\circ} \mathrm{C}\). Determine the mass flow rate of the refrigerant. Equation Transcription: 90°C 30°C 27°C 60°C Text Transcription: 134a 1 MPa 90 degree celsius 30 degree celsius 100 kPa 600 m^3/min 27 degree celsius 95 kPa 60 degree celsius

team is to be condensed in the condenser of a steam power plant at a temperature of \(50^{\circ} \mathrm{C}\) with cooling water from a nearby lake, which enters the tubes of the condenser at \(18^{\circ} \mathrm{C}\) at a rate of \(101 \mathrm{~kg} / \mathrm{s}\) and leaves at \(27^{\circ} \mathrm{C}\). Determine the rate of condensation of the steam in the condenser. Equation Transcription: 50°C 18°C 27°C Text Transcription: 50 degree celsius 18 degree celsius 101 kg/s 27 degree celsius

Problem 88P Two mass streams of the same ideal gas are mixed in a steady-flow chamber while receiving energy by heat transfer from the surroundings. The mixing process takes place at constant pressure with no work and negligible changes in kinetic and potential energies. Assume the gas has constant specific heats. (a) Determine the expression for the final temperature of the mixture in terms of the rate of heat transfer to the mixing chamber and the inlet and exit mass flow rates. ________________ (b) Obtain an expression for the volume flow rate at the exit of the mixing chamber in terms of the volume flow rates of the two inlet streams and the rate of heat transfer to the mixing chamber. ________________ (c) For the special case of adiabetic mixing, show that the exit volume flow rate is the sum of the two inlet volume flow rates.

Problem 89P Water enters a boiler at 500 psia as a saturated liquid and leaves at 600°F at the same pressure. Calculate the heat transfer per unit mass of water.

Problem 90P A 110-volt electrical heater is used to warm 0.3 m3/s of air at 100 kPa and 15°C to 100 kPa and 30°C. How much current in amperes must be supplied to this heater?

Problem 92P Water enters the tubes of a cold plate at 70°F with an average velocity of 40 ft/min and leaves at 105°F. The diameter of the tubes is 0.25 in. Assuming 15 percent of the heat generated is dissipated from the components to the surroundings by convection and radiation, and the remaining 85 percent is removed by the cooling water, determine the amount of heat generated by the electronic devices mounted on the cold plate.

Problem 93P A sealed electronic box is to be cooled by tap water flowing through the channels on two of its sides. It is specified that the temperature rise of the water not exceed 4°C. The power dissipation of the box is 2 kW, which is removed entirely by water. If the box operates 24 hours a day, 365 days a year, determine the mass flow rate of water flowing through the box and the amount of cooling water used per year.

The fan on a personal computer draws \(0.3 \mathrm{ft}^{3} / \mathrm{s}\) of air at \(14.7\) psia and \(70^{\circ} \mathrm{F}\) through the box containing the CPU and other components. Air leaves at \(14.7\) psia and \(83^{\circ} \mathrm{F}\). Calculate the electrical power, in \(\mathrm{kW}\), dissipated by the PC components. Equation Transcription: 70°F 83°F Text Transcription: 0.3 ft^3/s 70 degree fahrenheit 83 degree fahrenheit kW

The components of an electronic system dissizontal duct whose cross section is \(20 \mathrm{~cm} \times 20 \mathrm{~cm}\). The components in the duct are cooled by forced air that enters the duct at \(30^{\circ} \mathrm{C}\) and \(1 \mathrm{~atm}\) at a rate of \(0.6 \mathrm{~m}^{3} / \mathrm{min}\) and leaves at \(40^{\circ} \mathrm{C}\). Determine the rate of heat transfer from the outer surfaces of the duct to the ambient. Equation Transcription: 30°C 40°C Text Transcription: 180 W 1.4-m 20 cm times 20 cm 30 degree celsius 0.6 m^3/min 40 degree celsius

Problem 94P Repeat Prob. 5–93 for a power dissipation of 4 kW. (Reference Prob. 5–93) A sealed electronic box is to be cooled by tap water flowing through the channels on two of its sides. It is specified that the temperature rise of the water not exceed 4°C. The power dissipation of the box is 2 kW, which is removed entirely by water. If the box operates 24 hours a day, 365 days a year, determine the mass flow rate of water flowing through the box and the amount of cooling water used per year.

Repeat Prob. 5–95 for a circular horizontal duct of diameter \(20\ cm\). Equation Transcription: Text Transcription: 20 cm

Problem 97P Consider a hollow-core printed circuit board 9 cm I high and 18 cm long, dissipating a total of 15 W. The width of the air gap in the middle of the PCB is 0.25 cm. If the cooling air enters the 12-cm-wide core at 25°C and 1 atm at a rate of 0.8 L/s, determine the average temperature at which the air leaves the hollow core.

A computer cooled by a fan contains eight PCBs, each dissipating \(10 \mathrm{~W}\) power. The height of the PCBs is \(12 \mathrm{~cm}\) and the length is \(18 \mathrm{~cm}\). The cooling air is supplied by a 25-W fan mounted at the inlet. If the temperature rise of air as it flows through the case of the computer is not to exceed \(10^{\circ} \mathrm{C}\), determine (a) the flow rate of the air that the fan needs to deliver and (b) the fraction of the temperature rise of air that is due to the heat generated by the fan and its motor Equation Transcription: 10°C Text Transcription: 10 W 12 cm 18 cm 25-W 10 degree celsius

A long roll of 2-m-wide and 0.5-cm-thick 1-Mn manganese steel plate \(\left(\rho=7854 \mathrm{~kg} / \mathrm{m}^{3}\right.\) and \(c_{p}=\) \(0.434 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) ) coming off a furnace at \(820^{\circ} \mathrm{C}\) is to be quenched in an oil bath at \(45^{\circ} \mathrm{C}\) to a temperature of \(51.1^{\circ} \mathrm{C}\). If the metal sheet is moving at a steady velocity of \(10 \mathrm{~m} / \mathrm{min}\), determine the required rate of heat removal from the oil to keep its temperature constant at \(45^{\circ} \mathrm{C}\). Equation Transcription: 2-m 45°C 51.1°C Text Transcription: 2-m 0.5-cm rho=7854 kg/m^3 c_p= 0.434 kJ/kg dot degree celsius 820 degree celsius 45 degree celsius 51.1 degree celsius 10 m/min

Problem 99P A 4-m x 5-m x 6-m room is to be heated by an electric resistance heater placed in a short duct in the room. Initially, the room is at 15°C, and the local atmospheric pressure is 98 kPa. The room is losing heat steadily to the outside at a rate of 150 kJ/min. A 200-W fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of 40 kg/min. The duct can be assumed to be adiabatic, and there is no air leaking in or out of the room. If it takes 20 min for the room air to reach an average temperature of 25°C, find (a) the power rating of the electric heater and (b) the temperature rise that the air experiences each time it passes through the heater.

Problem 102P The hot-water needs of a household are to be met by heating water at 55°F to 180°F by a parabolic solar collector at a rate of 4 lbm/s. Water flows through a 1.25-in-diameter thin aluminum tube whose outer surface is black-anodized in order to maximize its solar absorption ability. The centerline of the tube coincides with the focal line of the collector, and a glass sleeve is placed outside the tube to minimize the heat losses. If solar energy is transferred to water at a net rate of 400 Btu/h per ft length of the tube, determine the required length of the parabolic collector to meet the hot-water requirements of this house.

Problem 103P A house has an electric heating system that consists of a 300-W fan and an electric resistance heating element placed in a duct. Air flows steadily through the duct at a rate of 0.6 kg/s and experiences a temperature rise of 7°C. The rate of heat loss from the air in the duct is estimated to be 300 W. Determine the power rating of the electric resistance heating element.

Problem 104P Steam enters a long, horizontal pipe with an inlet diameter of D1 = 16 cm at 2 MPa and 300°C with a velocity of 2.5 m/s. Farther downstream, the conditions are 1.8 MPa and 250°C, and the diameter is D2 = 14 cm. Determine (a) the mass flow rate of the steam and (b) the rate of heat transfer.

Problem 105P Refrigerant-134a enters the condenser of a refrigerator at 900 kPa and 60°C, and leaves as a saturated liquid at the same pressure. Determine the heat transfer from the refrigerant per unit mass.

Problem 106P Saturated liquid water is heated at constant pressure in a steady-flow device until it is a saturated vapor. Calculate the heat transfer, in kJ/kg, when the vaporization is done at a pressure of 500 kPa.

Problem 107P Water is heated in an insulated, constant-diameter tube by a 7-kW electric resistance heater. If the water enters the heater steadily at 20°C and leaves at 75°C, determine the mass flow rate of water.

Air at \(300 \mathrm{~K}\) and \(100 \mathrm{kPa}\) steadily flows into a hair dryer having electrical work input of 1500 W. Because of the size of the air intake, the inlet velocity of the air is negligible. The air temperature and velocity at the hair dryer exit are \(80^{\circ} \mathrm{C}\) and \(21 \mathrm{~m} / \mathrm{s}\), respectively. The flow process is both constant pressure and adiabatic. Assume air has constant specific heats evaluated at \(300 \mathrm{~K}\). ( a) Determine the air mass flow rate into the hair dryer, in \(\mathrm{kg} / \mathrm{s}\). (b) Determine the air volume flow rate at the hair dryer exit, in \(\mathrm{m}^{3} / \mathrm{s}\). Equation Transcription: 80°C Text Transcription: 300 K 100 kPa 80 degree celsius 21 m/s kg/s m^3/s

Reconsider Prob. 5–108. Using EES (or other) software, investigate the effect of the exit velocity on the mass flow rate and the exit volume flow rate. Let the exit velocity vary from 5 to \(25\ m/s\). Plot the mass flow rate and exit volume flow rate against the exit velocity, and discuss the results. Equation Transcription: Text Transcription: 25 m/s

ir enters the duct of an air-conditioning system at \(15 \mathrm{psia}\) and \(50^{\circ} \mathrm{F}\) at a volume flow rate of \(450 \mathrm{ft}^{3} / \mathrm{min}\). The diameter of the duct is \(10 \mathrm{in}\), and heat is transferred to the air in the duct from the surroundings at a rate of \(2 \mathrm{Btu} / \mathrm{s}\). Determine (a) the velocity of the air at the duct inlet and (b) the temperature of the air at the exit. Equation Transcription: 50°F Text Transcription: 50 degree fahrenheit 450 ft^3/min 2 Btu/s

Problem 111P A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries steam at 4 MPa. Now the valve is opened, and steam is allowed to flow into the tank until the pressure reaches 4 MPa, at which point the valve is closed. If the final temperature of the steam in the tank is 550°C, determine the temperature of the steam in the supply line and the flow work per unit mass of the steam.

A \(2-\mathrm{m}^{3}\) rigid insulated tank initially containing saturated water vapor at \(1 \mathrm{MPa}\) is connected through a valve to a supply line that carries steam at \(400^{\circ} \mathrm{C}\). Now the valve is opened, and steam is allowed to flow slowly into the tank until the pressure in the tank rises to \(2 \mathrm{MPa}\). At this instant the tank temperature is measured to be \(300^{\circ} \mathrm{C}\). Determine the mass of the steam that has entered and the pressure of the steam in the supply line. Equation Transcription: 400°C 300°C Text Transcription: 2-m^3 1 MPa 400 degree celsius 2 MPa 300 degree celsius

Consider a 35-L evacuated rigid bottle that is surrounded by the atmosphere at \(100 \mathrm{kPa}\) and \(22^{\circ} \mathrm{C}\). A valve at the neck of the bottle is now opened and the atmospheric air is allowed to flow into the bottle. The air trapped in the bottle eventually reaches thermal equilibrium with the atmosphere as a result of heat transfer through the wall of the bottle. The valve remains open during the process so that the trapped air also reaches mechanical equilibrium with the atmosphere. Determine the net heat transfer through the wall of the bottle during this filling process. Equation Transcription: 22°C Text Transcription: 35-L 100 kPa 22 degree celsius

A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries helium at \(200 \mathrm{kPa}\) and \(120^{\circ} \mathrm{C}\). Now the valve is opened, and helium is allowed to flow into the tank until the pressure reaches \(200 \mathrm{kPa}\), at which point the valve is closed. Determine the flow work of the helium in the supply line and the final temperature of the helium in the tank. Equation Transcription: 120°C Text Transcription: 200 kPa 120 degree celsius

Problem 115P A 0.2-m3 rigid tank equipped with a pressure regulator contains steam at 2 MPa and 300°C. The steam in the tank is now heated. The regulator keeps the steam pressure constant by letting out some steam, but the temperature inside rises, Determine the amount of heat transferred when the steam temperature reaches 500°C.

Problem 116P A 3-ft3 rigid tank initially contains saturated water vapor at 300°F. The tank is connected by a valve to a supply line that carries steam at 200 psia and 400°F. Now the valve is opened, and steam is allowed to enter the tank. Heat transfer takes place with the surroundings such that the temperature in the tank remains constant at 300°F at all times. The valve is closed when it is observed that one-half of the volume of the tank is occupied by liquid water. Find (a) the final pressure in the tank, (b) the amount of steam that has entered the tank, and (c) the amount of heat transfer.

A 4-L pressure cooker has an operating pressure of \(175 \mathrm{kPa}\). Initially, one-half of the volume is filled with liquid and the other half with vapor. If it is desired that the pressure cooker not run out of liquid water for \(1\ h\), determine the highest rate of heat transfer allowed. Equation Transcription: Text Transcription: 175 kPa 1 h

Problem 119P A scuba diver’s 2-ft3 air tank is to be filled with air from a compressed air line at 120 psia and 85°F. Initially, the air in this tank is at 20 psia and 60°F. Presuming that the tank is well insulated, determine the temperature and mass in the tank when it is filled to 120 psia.

An air-conditioning system is to be filled from a rigid container that initially contains \(5 \mathrm{~kg}\) of liquid R-134a at \(24^{\circ} \mathrm{C}\). The valve connecting this container to the air-conditioning system is now opened until the mass in the container is \(0.25 \mathrm{~kg}\), at which time the valve is closed. During this time, only liquid R-134a flows from the container. Presuming that the process is isothermal while the valve is open, determine the final quality of the R-134a in the container and the total heat transfer. Equation Transcription: 24°C Text Transcription: 5 kg 24 degree celsius 0.25 kg R-134a

An insulated, vertical piston-cylinder device initially contains \(10 \mathrm{~kg}\) of water, \(6 \mathrm{~kg}\) of which is in the vapor phase. The mass of the piston is such that it maintains a constant pressure of \(200 \mathrm{kPa}\) inside the cylinder. Now steam at \(0.5 \mathrm{MPa}\) and \(350^{\circ} \mathrm{C}\) is allowed to enter the cylinder from a supply line until all the liquid in the cylinder has vaporized. Determine (a) the final temperature in the cylinder and (b) the mass of the steam that has entered. Equation Transcription: 350°C Text Transcription: 10 kg 6 kg 200 kPa 0.5 MPa 350 degree celsius

Problem 121P Oxygen is supplied to a medical facility from ten 1.5-ft3 compressed oxygen tanks. Initially, these tanks are at 1500 psia and 80°F. The oxygen is removed from these tanks slowly enough that the temperature in the tanks remains at I 80°F. After two weeks, the pressure in the tanks is 300 psia. Determine the mass of oxygen used and the total heat transfer to the tanks.

Problem 122P A 0.06-m3 rigid tank initially contains refrigerant-134a at 0.8 MPa and 100 percent quality. The tank is connected by a valve to a supply line that carries refrigerant-134a at 1.2 MPa and 36°C. Now the valve is opened, and the refrigerant is allowed to enter the tank. The valve is closed when it is observed that the tank contains saturated liquid at 1.2 MPa. Determine (a) the mass of the refrigerant that has entered the tank and (b) the amount of heat transfer.

A \(0.3-\mathrm{m}^{3}\) rigid tank is filled with saturated liquid water at \(200^{\circ} \mathrm{C}\). A valve at the bottom of the tank is opened, and liquid is withdrawn from the tank. Heat is transferred to the water such that the temperature in the tank remains constant. Determine the amount of heat that must be transferred by the time one-half of the total mass has been withdrawn. Equation Transcription: 200°C Text Transcription: 0.3-m^3 200 degree celsius

A \(2-f t^{3}\) rigid tank contains saturated refrigerant\(134 \mathrm{a}\) at 160 psia. Initially, 5 percent of the volume is occupied by liquid and the rest by vapor. A valve at the top of the tank is now opened, and vapor is allowed to escape slowly from the tank. Heat is transferred to the refrigerant such that the pressure inside the tank remains constant. The valve is closed when the last drop of liquid in the tank is vaporized. Determine the total heat transfer for this process. Equation Transcription: Text Transcription: 2-ft^3 134a 160 psia

Problem 125P A 0.3-m3 rigid tank initially contains refrigerant- 134a at 14°C. At this state, 55 percent of the mass is in the vapor phase, and the rest is in the liquid phase. The tank is connected by a valve to a supply line where refrigerant at 1.4 MPa and 100°C flows steadily. Now the valve is opened slightly, and the refrigerant is allowed to enter the tank. When the pressure in the tank reaches 1 MPa, the entire refrigerant in the tank exists in the vapor phase only. At this point the valve is closed. Determine (a) the final temperature in the tank, (b) the mass of refrigerant that has entered the tank, and (c) the heat transfer between the system and the surroundings.

The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of \(0.5 \mathrm{~m}^{2}\), and the filling opening has an area of \(1 \mathrm{~m}^{2}\). During a two minute adiabatic flight maneuver, hot air enters the balloon at \(100 \mathrm{kPa}\) and \(35^{\circ} \mathrm{C}\) with a velocity of \(2 \mathrm{~m} / \mathrm{s}\); the air in the balloon remains at \(100 \mathrm{kPa}\) and \(35^{\circ} \mathrm{C}\); and air leaves the balloon through the air-release flap at velocity \(1 \mathrm{~m} / \mathrm{s}\). At the start of this maneuver, the volume of the balloon is \(75 \mathrm{~m}^{3}\). Determine the final volume of the balloon and work produced by the air inside the balloon as it expands the balloon skin. Equation Transcription: 35°C Text Transcription: 0.5 m^2 1 m^2 100 kPa 35 degree celsius 2 m/s 75 m^3

Problem 128P An insulated 0.15-m3 tank contains helium at 3 MPa and 130°C. A valve is now opened, allowing some helium to escape. The valve is closed when one-half of the initial mass has escaped. Determine the final temperature and pressure in the tank.

A balloon that initially contains \(50 \mathrm{~m}^{3}\) of steam at \(100 \mathrm{kPa}\) and \(150^{\circ} \mathrm{C}\) is connected by a valve to a large reservoir that supplies steam at \(150 \mathrm{kPa}\) and \(200^{\circ} \mathrm{C}\). Now the valve is opened, and steam is allowed to enter the balloon until the pressure equilibrium with the steam at the supply line is reached. The material of the balloon is such that its volume increases linearly with pressure. Heat transfer also takes place between the balloon and the surroundings, and the mass of the steam in the balloon doubles at the end of the process. Determine the final temperature and the boundary work during this process. the final temperature and the boundary work during this process. Equation Transcription: 150°C 200°C Text Transcription: 50 m^3 100 kPa 150 degree celsius 150 kPa 200 degree celsius

An insulated \(40-\mathrm{ft}^{3}\) rigid tank contains air at 50 psia and \(120^{\circ} \mathrm{F} . \mathrm{A}\) valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. The air temperature during this process is maintained constant by an electric resistance heater placed in the tank. Determine the electrical work done during this process. Equation Transcription: 120°F Text Transcription: 40-ft^3 120 degree fahrenheit

Problem 130P A vertical piston-cylinder device initially contains I 0.2 m3 of air at 20°C. The mass of the piston is such that it I maintains a constant pressure of 300 kPa inside. Now a I valve connected to the cylinder is opened, and air is allowed to escape until the volume inside the cylinder is decreased by one-half. Heat transfer takes place during the process so K that the temperature of the air in the cylinder remains constant. Determine (a) the amount of air that has left the cylinder and (b) the amount of heat transfer.

The air in an insulated, rigid compressed-air tank whose volume is \(0.5 \mathrm{~m}^{3}\) is initially at \(4000 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\). Enough air is now released from the tank to reduce the pressure to \(2000 \mathrm{kPa}\). Following this release, what is the temperature of the remaining air in the tank? Equation Transcription: 20°C Text Transcription: 0.5 m^3 4000 kPa 20 degree celsius 2000 kPa

Problem 135P The air in a 6-m x 5-m x 4-m hospital room is to be completely replaced by conditioned air every 15 min. If the average air velocity in the circular air duct leading to the room is not to exceed 5 m/s, determine the minimum diameter of the duct.

An insulated vertical piston-cylinder device initially contains \(0.8 \mathrm{~m}^{3}\) of refrigerant-\(134a\) at \(1.4 \mathrm{MPa}\) and \(120^{\circ} \mathrm{C}\). A linear spring at this point applies full force to the piston. A valve connected to the cylinder is now opened, and refrigerant is allowed to escape. The spring unwinds as the piston moves down, and the pressure and volume drop to \(0.7 \mathrm{MPa}\) and \(0.5 \mathrm{~m}^{3}\) at the end of the process. Determine (a) the amount of refrigerant that has escaped and (b) the final temperature of the refrigerant. Equation Transcription: 120°C Text Transcription: 0.8 m^3 120 degree celsius 0.5 m^3

Problem 132P A vertical piston–cylinder device initially contains 0.01 m3 of steam at 200°C. The mass of the frictionless piston is such that it maintains a constant pressure of 500 kPa inside. Now steam at 1 MPa and 350°C is allowed to enter the cylinder from a supply line until the volume inside doubles. Neglecting any heat transfer that may have taken place during the process, determine (a) the final temperature of the steam in the cylinder and (b) the amount of mass that has entered.

A vertical piston-cylinder device initially contains \(0.25 \mathrm{~m}^{3}\) of air at \(600 \mathrm{kPa}\) and \(300^{\circ} \mathrm{C}\). A valve connected to the cylinder is now opened, and air is allowed to escape until three-quarters of the mass leave the cylinder at which point the volume is \(0.05 \mathrm{~m}^{3}\). Determine the final temperature in the cylinder and the boundary work during this process. Equation Transcription: 300°C Text Transcription: 0.25 m^3 600 kPa 300 degree celsius 0.05 m^3

A long roll of 1 -m-wide and \(0.5\)-cm-thick 1-Mn manganese steel plate \(\left(\rho=7854 \mathrm{~kg} / \mathrm{m}^{3}\right)\) coming off a furnace is to be quenched in an oil bath to a specified temperature. If the metal sheet is moving at a steady velocity of \(10 \mathrm{~m} / \mathrm{min}\), determine the mass flow rate of the steel plate through the oil bath. Equation Transcription: Text Transcription: 0.5-cm rho= 7854 kg/m^3

Problem 137P Air at 4.18 kg/m3 enters a nozzle that has an inlet-to-exit area ratio of 2:1 with a velocity of 120 m/s and leaves with a velocity of 380 m/s. Determine the density of air at the exit.

Problem 139P Saturated refrigerant-134a vapor at 34°C is to be condensed as it flows in a 1-cm-diameter tube at a rate of 0.1 kg/min. Determine the rate of heat transfer from the refrigerant. What would your answer be if the condensed refrigerant is cooled to 20°C?

A steam turbine operates with \(1.6 \mathrm{MPa}\) and \(350^{\circ} \mathrm{C}\) steam at its inlet and saturated vapor at \(30^{\circ} \mathrm{C}\) at its exit. The mass flow rate of the steam is \(22 \mathrm{~kg} / \mathrm{s}\), and the turbine produces \(12,350 \mathrm{~kW}\) of power. Determine the rate at which heat is lost through the casing of this turbine. Equation Transcription: 350°C 30°C Text Transcription: 1.6 MPa 350 degree celsius 30 degree celsius 22 kg/s 12,350 kW

Problem 138P An air compressor compresses 15 L/s of air at 120 kPa and 20°C to 800 kPa and 300°C while consuming 6.2 kW of power. How much of this power is being used to increase the pressure of the air versus the power needed to move the fluid through the compressor?

Problem 141P Nitrogen gas flows through a long, constant-diameter adiabatic pipe. It enters at 100 psia and 120°F and leaves at 50 psia and 70°F. Calculate the velocity of the nitrogen at the pipe's inlet and outlet.

Problem 142P A 110-V electric hot-water heater warms 0.1 L/s of water from 18 to 30°C. Calculate the current in amperes that must be supplied to this heater.

Problem 143P Steam enters a long, insulated pipe at 1200 kPa, 250°C, and 4 m/s, and exits at 1000 kPa. The diameter of the pipe is 0.15 m at the inlet, and 0.1 m at the exit. Calculate the mass flow rate of the steam and its speed at the pipe outlet.

Problem 144P Air enters a pipe at 65°C and 200 kPa and leaves at 60°C and 175 kPa. It is estimated that heat is lost from the pipe in the amount of 3.3 kJ per kg of air flowing in the pipe. The diameter ratio for the pipe is D1/D2= 1.4. Using constant specific heats for air, determine the inlet and exit velocities of the air.

Problem 146P In a gas-fired boiler, water is boiled at 180°C by hot gases flowing through a stainless steel pipe submerged in water. If the rate of heat transfer from the hot gases to water is 48 kJ/s, determine the rate of evaporation of water.

Problem 145P Steam enters a nozzle with a low velocity at 150°C and 200 kPa, and leaves as a saturated vapor at 75 kPa. There is a heat transfer from the nozzle to the surroundings in the amount of 26 kJ for every kilogram of steam flowing through the nozzle. Determine (a) the exit velocity of the steam and (b) the mass flow rate of the steam at the nozzle entrance if the nozzle exit area is 0.001 m2.

Saturated steam at 1 atm condenses on a vertical plate that is maintained at \(90^{\circ} \mathrm{C}\) by circulating cooling water through the other side. If the rate of heat transfer by condensation to the plate is \(180 \mathrm{~kJ} / \mathrm{s}\), determine the rate at which the condensate drips off the plate at the bottom. Equation Transcription: 90°C Text Transcription: 1 atm 90 degree celsius 180 kJ/s

Problem 148P The condenser of a steam power plant operates at a pressure of 0.95 psia. The condenser consists of 144 horizontal tubes arranged in a 12 x 12 square array. Steam condenses on the outer surfaces of the tubes whose inner and outer diameters are 1 in and 1.2 in, respectively. If steam is to be condensed at a rate of 6800 lbm/h and the temperature rise of the cooling water is limited to 8°F, determine (a) the rate of heat transfer from the steam to the cooling water and (b) the averagevelocity of the cooling water through the tubes.

Problem 149P In large steam power plants, the feedwater is frequently heated in a closed feedwater heater by using steam extracted from the turbine at some stage. Steam enters the feedwater heater at 1 MPa and 200°C and leaves as saturated liquid at the same pressure. Feedwater enters the heater at 2.5 MPa and 50°C and leaves at 10°C below the exit temperature of the steam. Determine the ratio of the mass flow rates of the extracted steam and the feedwater.

Problem 150P Cold water enters a steam generator at 20°C and leaves as saturated vapor at 200°C. Determine the fraction of heat used in the steam generator to preheat the liquid water from 20°C to the saturation temperature of 200°C.

Problem 151P Cold water enters a steam generator at 20°C and leaves as saturated vapor at the boiler pressure. At what pressure will the amount of heat needed to preheat the water to saturation temperature be equal to the heat needed to vaporize the liquid at the boiler pressure?

An ideal gas expands in an adiabatic turbine from \(1200 \mathrm{~K}\) and \(900 \mathrm{kPa}\) to \(800 \mathrm{~K}\). Determine the turbine inlet volume flow rate of the gas, in \(\mathrm{m}^{3} / \mathrm{s}\), required to produce turbine work output at the rate of \(650 \mathrm{~kW}\). The average values of the specific heats for this gas over the temperature range and the gas constant are \(c_{p}=1.13 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}, c_{v}=\) \(0.83 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}\), and \(R=0.30 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}\). Equation Transcription: Text Transcription: 1200 K 900kPa 800 K m^3/s 650 kW c_p=1.13 kJ/kg times K,c_v=0.83 kJ/kg times K R=0.30 kJ/kg times K

Problem 153P Chickens with an average mass of 2.2 kg and average specific heat of 3.54 kJ/kg·°C are to be cooled by chilled water that enters a continuous-flow-type immersion chiller at 0.5°C. Chickens are dropped into the chiller at a uniform temperature of 15°C at a rate of 500 chickens per hour and are cooled to an average temperature of 3°C before they are taken out. The chiller gains heat from the surroundings at a rate of 200 kJ/h. Determine (a) the rate of heat removal from the chickens, in kW, and (b) the mass flow rate of water, in kg/s, if the temperature rise of water is not to exceed 2°C.

Problem 156P A glass bottle washing facility uses a well-agitated hot-water bath at 50°C that is placed on the ground. The bottles enter at a rate of 450 per minute at an ambient temperature of 20°C and leave at the water temperature. Each bottle has a mass of 150 g and removes 0.2 g of water as it leaves the bath wet. Make-up water is supplied at 15°C. Disregarding any heat losses from the outer surfaces of the bath, determine the rate at which (a) water and (b) heat must be supplied to maintain steady operation.

Problem 154P Repeat Prob. 5–162 assuming heat gain of the chiller is negligible.

Problem 155P A refrigeration system is being designed to cool eggs (?= 67.4 lbm/ft3 and cp= 0.80 BtuAbm·°F) with an average mass of 0.14 lbm from an initial temperature of 90°F to a final average temperature of 50°F by air at 34°F at a rate of 10,000 eggs per hour. Determine (a) the rate of heat removal from the eggs, in Btu/h and (b) the required volume flow rate of air, in ft3/h, if the temperature rise of air is not to exceed 10°F.

The heat of hydration of dough, which is \(15 \mathrm{~kJ} / \mathrm{kg}\), will raise its temperature to undesirable levels unless some cooling mechanism is utilized. A practical way of absorbing the heat of hydration is to use refrigerated water when kneading the dough. If a recipe calls for mixing \(2 \mathrm{~kg}\) of flour with \(1 \mathrm{~kg}\) of water, and the temperature of the city water is \(15^{\circ} \mathrm{C}\), determine the temperature to which the city water must be cooled before mixing in order for the water to absorb the entire heat of hydration when the water temperature rises to \(15^{\circ} \mathrm{C}\). Take the specific heats of the flour and the water to be \(1.76\) and \(4.18 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\), respectively. Equation Transcription: 15°C °C Text Transcription: 15 kJ/kg 2 kg 1 kg 15 degree celsius 1.76 4.18 kJ/kg dot degree celsius

Long aluminum wires of diameter \(5 \mathrm{~mm}(\rho=2702\) \(\mathrm{kg} / \mathrm{m}^{3}\) and \(c_{p}=0.896 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) ) are extruded at a temperature of \(350^{\circ} \mathrm{C}\) and are cooled to \(50^{\circ} \mathrm{C}\) in atmospheric air at \(25^{\circ} \mathrm{C}\). If the wire is extruded at a velocity of \(8 \mathrm{~m} / \mathrm{min}\), determine the rate of heat transfer from the wire to the extrusion room. Equation Transcription: °C 350°C 50°C 25°C Text Transcription: 5 mm (rho= 2702 kg/m^3 c_p=0.896 J/kg dot degree celsius 350 degree celsius 50 degree celsius 25 degree celsius

Problem 159P Repeat Prob. 5–167 for a copper wire (p = 8950 kg/m3 and cp =0.383 kJ/kg-°C).

Problem 160P Steam at 80 psia and 400°F is mixed with water at 60°F and 80 psia steadily in an adiabatic device. Steam enters the device at a rate of 0.05 lbm/s, while the water enters at 1 lbm/s. Determine the temperature of the mixture leaving this device when the outlet pressure is 80 psia.

A constant-pressure \(R-134a\) vapor separation unit separates the liquid and vapor portions of a saturated mixture into two separate outlet streams. Determine the flow power needed to pass \(6 L/s\) of \(R-134a\) at \(320 \mathrm{kPa}\) and 55 percent quality through this unit. What is the mass flow rate, in \(kg/s\), of the two outlet streams? Equation Transcription: Text Transcription: R-134a 6 L/s 320 kPa kg/s

Problem 162P Consider two identical buildings: one in Los Angeles, California, where the atmospheric pressure is 101 kPa and the other in Denver, Colorado, where the atmospheric pressure is 83 kPa. Both buildings are maintained at 21°C, and the infiltration rate for both buildings is 1.2 air changes per hour (ACH). That is, the entire air in the building is replaced completely by the outdoor air 1.2 times per hour on a day when the outdoor temperature at both locations is 10°C. Disregarding latent heat, determine the ratio of the heat losses by infiltration at the two cities.

Problem 163P It is well established that indoor air quality (IAQ) has a significant effect on general health and productivity of employees at a workplace. A study showed that enhancing IAQ by increasing the building ventilation from 5 cfm (cubic feet per minute) to 20 cfm increased the productivity by 0.25 percent, valued at $90 per person per year, and decreased the respiratory illnesses by 10 percent for an average annual savings of $39 per person while increasing the annual energy consumption by $6 and the equipment cost by about $4 per person per year (ASHRAE Journal,December 1998). For a workplace with 120 employees, determine the net monetary benefit of installing an enhanced IAQ system to the employer per year.

During the inflation and deflation of a safety airbag in an automobile, the gas enters the airbag with a specific volume of \(15 \mathrm{ft}^{3} / \mathrm{lbm}\) and at a mass flow rate that varies with time as illustrated in Fig. P5-165E. The gas leaves this airbag with a specific volume of \(13 \mathrm{ft}^{3} / \mathrm{lbm}\), with a mass flow rate that varies with time, as shown in Fig. P5-165E. Plot the volume of this bag (i.e., airbag size) as a function of time, in \(\mathrm{ft}^{3}\). Equation Transcription: Text Transcription: 15 ft^3/lbm 13 ft^3/lbm ft^3

The ventilating fan of the bathroom of a building has a volume flow rate of \(30 \mathrm{~L} / \mathrm{s}\) and runs continuously. The building is located in San Francisco, California, where the average winter temperature is \(12.2^{\circ} \mathrm{C}\), and is maintained at \(22^{\circ} \mathrm{C}\) at all times. The building is heated by electricity whose unit cost is \(\$ 0.12 / \mathrm{kWh}\). Determine the amount and cost of the heat "vented out" per month in winter. Equation Transcription: °C °C Text Transcription: 12.2 degree celsius 22 degree celsius $0.12/kWh 30 L/s

Problem 166P Determine the rate of sensible heat loss from a building due to infiltration if the outdoor air at -5°C and 95 kPa enters the building at a rate of 60 L/s when the indoors is maintained at 25°C.

An air-conditioning system requires airflow at the main supply duct at a rate of \(130 \mathrm{~m}^{3} / \mathrm{min}\). The average velocity of air in the circular duct is not to exceed \(8 \mathrm{~m} / \mathrm{s}\) to avoid excessive vibration and pressure drops. Assuming the fan converts 80 percent of the electrical energy it consumes into kinetic energy of air, determine the size of the electric motor needed to drive the fan and the diameter of the main duct. Take the density of air to be \(1.20 \mathrm{~kg} / \mathrm{m}^{3}\). Equation Transcription: Text Transcription: 130 m^3/min 8 m/s 1.20 kg/m^3

Problem 168P The maximum flow rate of standard shower heads is about 3.5 gpm (13.3 L/min) and can be reduced to 2.75 gpm (10.5 L/min) by switching to low-flow shower heads that are equipped with flow controllers. Consider a family of four, with each person taking a 5-min shower every morning. City water at 15°C is heated to 55°C in an electric water heater and tempered to 42°C by cold water at the T-elbow of the shower before being routed to the shower heads. Assuming a constant specific heat of 4.18 kJ/kg·°C for water, determine (a) the ratio of the flow rates of the hot and cold water as they enter the T-elbow and (b) the amount of electricity that will be saved per year, in kWh, by replacing the standard shower heads by the low-flow ones.

An adiabatic air compressor is to be powered by a direct-coupled adiabatic steam turbine that is also driving a generator. Steam enters the turbine at \(12.5 \mathrm{MPa}\) and \(500^{\circ} \mathrm{C}\) at a rate of \(25 \mathrm{~kg} / \mathrm{s}\) and exits at \(10 \mathrm{kPa}\) and a quality of \(0.92\). Air enters the compressor at \(98 \mathrm{kPa}\) and \(295 \mathrm{~K}\) at a rate of \(10 \mathrm{~kg} / \mathrm{s}\) and exits at \(1 \mathrm{MPa}\) and \)620 \mathrm{~K}\). Determine the net power delivered to the generator by the turbine. Equation Transcription: 500°C Text Transcription: 12.5 MPa 500 degree celsius 25 kg/s 10 kPa 98 kPa 295 K 10 kg/s 620 K

Determine the power input for a compressor that compresses helium from \(110 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) to \(400 \mathrm{kPa}\) and \(200^{\circ} \mathrm{C}\). Helium enters this compressor through a \(0.1-\mathrm{m}^{2}\) pipe at a velocity of \(9 \mathrm{~m} / \mathrm{s}\). Equation Transcription: 20°C 200°C Text Transcription: 110 kPa 20 degree celsius 400 kPa 200 degree celsius 0.1-m^2 9 m/s

Problem 173P Submarines change their depth by adding or removing air from rigid ballast tanks, thereby displacing seawater in the tanks. Consider a submarine that has a 700 m3 air-ballast t tank originally partially filled with 100 m3 of air at 1500 kPa and 15°C. For the submarine to surface, air at 1500 kPa and 20°C is pumped into the ballast tank, until it is entirely filled with air. The tank is filled so quickly that the process is adiabatic and the seawater leaves the tank at 15°C. Determine the final temperature and mass of the air in the ballast tank.

Refrigerant \(134 \mathrm{a}\) enters a compressor with a mass flow rate of \(5 \mathrm{~kg} / \mathrm{s}\) and a negligible velocity. The refrigerant enters the compressor as a saturated vapor at \(10^{\circ} \mathrm{C}\) and leaves the compressor at \(1400 \mathrm{kPa}\) with an enthalpy of \(281.39 \mathrm{~kJ} / \mathrm{kg}\) and a velocity of \(50 \mathrm{~m} / \mathrm{s}\). The rate of work done on the refrigerant is measured to be \(132.4 \mathrm{~kW}\). If the elevation change between the compressor inlet and exit is negligible, determine the rate of heat transfer associated with this process, in \(\mathrm{kW}\). Equation Transcription: 10°C Text Transcription: 134a 5 kg/s 10 degree celsius 1400 kPa 281.39 kJ/kg 50 m/s 132.4 kW kW

Problem 174P In the preceding problem, presume that air is added to the tank in such a way that the temperature and pressure of the air in the tank remain constant. Determine the final mass of the air in the ballast tank under this condition. Also determine the total heat transfer while the tank is being filled in this manner.

Water flows through a shower head steadily at a rate of \(10 \mathrm{~L} / \mathrm{min}\). An electric resistance heater placed in the water pipe heats the water from 16 to \(43^{\circ} \mathrm{C}\). Taking the density of water to be \(1 \mathrm{~kg} / \mathrm{L}\), determine the electric power input to the heater, in \(\mathrm{kW}\). In an effort to conserve energy, it is proposed to pass the drained warm water at a temperature of \(39^{\circ} \mathrm{C}\) through a heat exchanger to preheat the incoming cold water. If the heat exchanger has an effectiveness of \(0.50\\) (that is, it recovers only half of the energy that can possibly be transferred from the drained water to incoming cold water), determine the electric power input required in this case. If the price of the electric energy is \(11.5 \mathrm{c} / \mathrm{kWh}\]), determine how much money is saved during a 10-min shower as a result of installing this heat exchanger. Equation Transcription: 43°C Text Transcription: 10 L/min 43°C 1 kg/L 39°C 11.5 ¢/kWh

A tank with an internal volume of \(1 \mathrm{~m}^{3}\) contains air at \(800 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\). A valve on the tank is opened allowing air to escape and the pressure inside quickly drops to \(150 \mathrm{kPa}\), at which point the valve is closed. Assume there is negligible heat transfer from the tank to the air left in the tank. (a) Using the approximation \(h_{e} \approx\) constant \(=h_{e, \text { avg }}=\) \(0.5\left(h_{1}+h_{2}\right)\), calculate the mass withdrawn during the process. (b) Consider the same process but broken into two parts. That is, consider an intermediate state at \(P_{2}=400 \mathrm{kPa}\), calculate the mass removed during the process from \(P_{1}=800 \mathrm{kPa}\) to \(P_{2}\) and then the mass removed during the process from \(P_{2}\) to \(P_{3}=150 \mathrm{kPa}\), using the type of approximation used in part (a), and add the two to get the total mass removed. (c) Calculate the mass removed if the variation of \(h_{e}\) is accounted for. Equation Transcription: Text Transcription: 1 m^3 800 kPa 25C 150kPa h_e anstant =h_e=mg= 0.5(h_1+h_2) P_2=400kPa P_1=800kPa P_2 P_3=150kPa h_e

A liquid R-134a bottle has an internal volume of \(0.0015 \mathrm{~m}^{3}\). Initially it contains \(0.55 \mathrm{~kg}\) of R-134a (saturated mixture) at \(26^{\circ} \mathrm{C}\). A valve is opened and \(\mathrm{R}-134 \mathrm{a}\) vapor only (no liquid) is allowed to escape slowly such that temperature remains constant until the mass of R-134a remaining is \(0.15 \mathrm{~kg}\). Find the heat transfer necessary with the surroundings to maintain the temperature and pressure of the R-134a constant. Equation Transcription: R-134a 26°C Text Transcription: R-134a 0.55 kg 26 degree celsius 0.15 kg

Steam enters a turbine steadily at \(7 \mathrm{MPa}\) and \(600^{\circ} \mathrm{C}\) with a velocity of \(60 \mathrm{~m} / \mathrm{s}\) and leaves at \(25 \mathrm{kPa}\) with a quality of 95 percent. A heat loss of \(20 \mathrm{~kJ} / \mathrm{kg}\) occurs during the process. The inlet area of the turbine is \(150 \mathrm{~cm}^{2}\), and the exit area is \(1400 \mathrm{~cm}^{2}\). Determine \((a)\) the mass flow rate of the steam, \((b)\) the exit velocity, and \((c)\) the power output. Equation Transcription: 600°C Text Transcription: 7 MPa 600 degree celsius 60 m/s 25 kPa 150 cm^2 1400 cm^2

Reconsider Prob. 5-179. Using EES (or other) software, investigate the effects of turbine exit area and turbine exit pressure on the exit velocity and power output of the turbine. Let the exit pressure vary from 10 to \(50 \mathrm{kPa}\) (with the same quality), and the exit area to vary from 1000 to \(3000 \mathrm{~cm}^{2}\). Plot the exit velocity and the power outlet against the exit pressure for the exit areas of 1000,2000 , and \(3000 \mathrm{~cm}^{2}\), and discuss the results. Equation Transcription: Text Transcription: 50 kPa 3000 cm^2

Problem 181P In large gas-turbine power plants, air is preheated by the exhaust gases in a heat exchanger called the regenerator before it enters the combustion chamber. Air enters the regenerator at 1 MPa and 550 K at a mass flow rate of 800 kg/min. Heat is transferred to the air at a rate of 3200 kJ/s. Exhaust gases enter the regenerator at 140 kPa and. 800 K and leave at 130 kPa and 600 K. Treating the exhaust gases as air, determine (a) the exit temperature of the air and (b) the mass flow rate of exhaust gases.

Problem 182P It is proposed to have a water heater that consists of an insulated pipe of 7.5-cm diameter and an electric resistor inside. Cold water at 20°C enters the heating section steadily at a rate of 24 L/min. If water is to be heated to 48°C, determine (a) the power rating of the resistance heater and (b) the average velocity of the water in the pipe.

An insulated vertical piston-cylinder device (E) initially contains \(0.11 \mathrm{~m}^{3}\) of air at \(150 \mathrm{kPa}\) and \(22^{\circ} \mathrm{C}\). At this state, a linear spring touches the piston but exerts no force on it. The cylinder is connected by a valve to a line that supplies air at \(700 \mathrm{kPa}\) and \(22^{\circ} \mathrm{C}\). The valve is opened, and air from the high-pressure line is allowed to enter the cylinder. The valve is turned off when the pressure inside the cylinder reaches \(600 \mathrm{kPa}\). If the enclosed volume inside the cylinder doubles during this process, determine \((a)\) the mass of air that entered the cylinder, and \((b)\) the final temperature of the air inside the cylinder. Equation Transcription: 22°C Text Transcription: 0.11 m^3 150 kPa 22 degree celsius 600 kPa

Problem 184P A piston-cylinder device initially contains 2 kg of refrigerant-134a at 800 kPa and 80°C. At this state, the piston is touching on a pair of stops at the top. The mass of the piston is such that a 500-kPa pressure is required to move it. A valve at the bottom of the tank is opened, and R-134a is withdrawn from the cylinder. After a while, the piston is observed to move and the valve is closed when half of the refrigerant is withdrawn from the tank and the temperature in the tank drops to-20°C. Determine (a) the work done and (b) the heat transfer.

In a single-flash geothermal power plant, geothermal water enters the flash chamber (a throttling valve) at \(230^{\circ} \mathrm{C}\) as a saturated liquid at a rate of \(50 \mathrm{~kg} / \mathrm{s}\). The steam resulting from the flashing process enters a turbine and leaves at \(20 \mathrm{kPa}\) with a moisture content of 5 percent. Determine the temperature of the steam after the flashing process and the power output from the turbine if the pressure of the steam at the exit of the flash chamber is (a) \(1 \mathrm{MPa}\), (b) \(500 \mathrm{kPa}\), (c) \(100 \mathrm{kPa}\), (d) \(50 \mathrm{kPa}\). Equation Transcription: 230°C Text Transcription: 230 degree celsius 50 kg/s 20 kPa 1 MPa 500 kPa 100 kPa 50 kPa

A piston-cylinder device initially contains \(1.2 \mathrm{~kg}\) of air at \(700 \mathrm{kPa}\) and \(200^{\circ} \mathrm{C}\). At this state, the piston is touching on a pair of stops. The mass of the piston is such that \(600-\mathrm{kPa}\) pressure is required to move it. A valve at the bottom of the tank is opened, and air is withdrawn from the cylinder. The valve is closed when the volume of the cylinder decreases to 80 percent of the initial volume. If it is estimated that \(40 \mathrm{~kJ}\) of heat is lost from the cylinder, determine \((a)\) the final temperature of the air in the cylinder, (b) the amount of mass that has escaped from the cylinder, and \((c)\) the work done. Use constant specific heats at the average temperature. Equation Transcription: 200°C Text Transcription: 1.2 kg 700 kPa 200 degree celsius 600-kPa 40 kJ

A building with an internal volume of \(400 \mathrm{~m}^{3}\) is to be heated by a \(30-\mathrm{kW}\) electric resistance heater placed in the duct inside the building. Initially, the air in the building is at \(14^{\circ} \mathrm{C}\), and the local atmospheric pressure is \(95 \mathrm{kPa}\). The building is losing heat to the surroundings at a steady rate of \(450 \mathrm{~kJ} / \mathrm{min}\). Air is forced to flow through the duct and the heater steadily by a 250 - W fan, and it experiences a temperature rise of \(5^{\circ} \mathrm{C}\) each time it passes through the duct, which may be assumed to be adiabatic. (a) How long will it take for the air inside the building to reach an average temperature of \(24^{\circ} \mathrm{C}\) ? (b) Determine the average mass flow rate of air through the duct. Equation Transcription: 14°C 5°C 24°C Text Transcription: 400 m^3 14 degree celsius 95 kPa 450 kJ/min 5 degree celsius 24 degree celsius 250-W

The turbocharger of an internal combustion engine consists of a turbine and a compressor. Hot exhaust gases flow through the turbine to produce work and the work output from the turbine is used as the work input to the compressor. The pressure of ambient air is increased as it flows through the compressor before it enters the engine cylinders. Thus, the purpose of a turbocharger is to increase the pressure of air so that more air gets into the cylinder. Consequently, more fuel can be burned and more power can be produced by the engine. In a turbocharger, exhaust gases enter the turbine at \(400^{\circ} \mathrm{C}\) and \(120 \mathrm{kPa}\) at a rate of \(0.02 \mathrm{~kg} / \mathrm{s}\) and leave at \(350^{\circ} \mathrm{C}\). Air enters the compressor at \(50^{\circ} \mathrm{C}\) and \(100 \mathrm{kPa}\) and leaves at \(130 \mathrm{kPa}\) at a rate of \(0.018 \mathrm{~kg} / \mathrm{s}\). The compressor increases the air pressure with a side effect: It also increases the air temperature, which increases the possibility of a gasoline engine to experience an engine knock. To avoid this, an aftercooler is placed after the compressor to cool the warm air by cold ambient air before it enters the engine cylinders. It is estimated that the aftercooler must decrease the air temperature below \(80^{\circ} \mathrm{C}\) if knock is to be avoided. The cold ambient air enters the aftercooler at \(30^{\circ} \mathrm{C}\) and leaves at \(40^{\circ} \mathrm{C}\). Disregarding any frictional losses in the turbine and the compressor and treating the exhaust gases as air, determine (a) the temperature of the air at the compressor outlet and (b) the minimum volume flow rate of ambient air required to avoid knock. Equation Transcription: 400°C 50°C 350°C 30°C 40°C Text Transcription: 400 degree celsius 120 kPa 0.02 kg/s 50 degree celsius 350 degree celsius 100 kPa 0.018 kg/s 30 degree celsius 40 degree celsius

A \(D_{0}=10\)-m-diameter tank is initially filled with water \(2 \mathrm{~m}\) above the center of a \9D=10\)-cm-diameter valve near the bottom. The tank surface is open to the atmosphere, and the tank drains through a \(L=100\)-m-long pipe connected to the valve. The friction factor of the pipe is given to be \(f=0.015\), and the discharge velocity is expressed as \(V=\sqrt{\frac{2 g z}{1.5+f L D}}\) where \(z\) is the water height above the center of the valve. Determine (a) the initial discharge velocity from the tank and (b) the time required to empty the tank. The tank can be considered to be empty when the water level drops to the center of the valve. Equation Transcription: Text Transcription: D_0=10?m D=10?cm L=100 f=0.015 V=square root 2gz/1.5+fLD

Problem 190P The velocity of a liquid flowing in a circular pipe of radius R varies from zero at the wall to a maximum at the pipe center. The velocity distribution in the pipe can be represented as V(r),where r is the radial distance from the pipe center. Based on the definition of mass flow rate m, obtain a relation for the average velocity in terms of V(r), R, and r.

Two streams of the same ideal gas having different mass flow rates and temperatures are mixed in a steady-flow, adiabatic mixing device. Assuming constant specific heats, find the simplest expression for the mixture temperature written in the form \(T_{3}=f\left(\frac{\dot{m}_{1}}{\dot{m}_{3}}, \frac{\dot{m}_{2}}{\dot{m}_{3}}, T_{1}, T_{2}\right)\) Equation Transcription: Text Transcription: T_3=f(dot m_1/dot m_3,dot m_2/dot m_3,T_1,T_2)

Steam is compressed by an adiabatic compressor from \(0.2 \mathrm{MPa}\) and \(150^{\circ} \mathrm{C}\) to \(2.5 \mathrm{MPa}\) and \(250^{\circ} \mathrm{C}\) at a rate of \(1.30 \mathrm{~kg} / \mathrm{s}\). The power input to the compressor is (a) \(144 \mathrm{~kW}\) (b) \(234 \mathrm{~kW}\) (c) \(438 \mathrm{~kW}\) (d) \(717 \mathrm{~kW}\) (e) \(901 \mathrm{~kW}\) Equation Transcription: 150°C 250°C Text Transcription: 0.2 MPa 150 degree celsius 2.5 MPa 250 degree celsius 1.30 kg/s 144 kW 234 kW 438 kW 717 kW 901 kW

Problem 193P Steam enters a diffuser steadily at 0.5 MPa, 300°C, and 122 m/s at a rate of 3.5 kg/s. The inlet area of the diffuser is (a) 15 cm2 ________________ (b) 50 cm2 ________________ (c) 105 cm2 ________________ (d) 150cm2 ________________ (e) 190 cm2

Problem 194P An adiabatic heat exchanger is used to heat cold water at 15°C entering at a rate of 5 kg/s by hot air at 90°C entering also at a rate of 5 kg/s. If the exit temperature of hot air is 20°C, the exit temperature of cold water is (a) 27°C ________________ (b) 32°C ________________ (c) 52°C ________________ (d) 85°C ________________ (e) 90°C

Problem 196P An adiabatic heat exchanger is used to heat cold water at 15°C entering at a rate of 5 kg/s by hot water at 90°C entering at a rate of 4 kg/s. If the exit temperature of hot water is 50°C, the exit temperature of cold water is (a) 42°C ________________ (b) 47°C ________________ (c) 55°C ________________ (d) 78°C ________________ (e) 90°C

Problem 195P A heat exchanger is used to heat cold water at 15°C entering at a rate of 2 kg/s by hot air at 85°C entering at a rate of 3 kg/s. The heat exchanger is not insulated and is losing heat at a rate of 25 kJ/s. If the exit temperature of hot air is 20°C, the exit temperature of cold water is (a) 28°C ________________ (b) 35°C ________________ (c) 38°C ________________ (d) 41°C ________________ (e) 80°C

Problem 197P In a shower, cold water at 10°C flowing at a rate of 5 kg/min is mixed with hot water at 60°C flowing at a rate of 2 kg/min. The exit temperature of the mixture is (a) 24.3T ________________ (b) 35.0T ________________ (c) 40.0°C ________________ (d) 44.3°C ________________ (e) 55.2°C

Problem 199P Hot combustion gases (assumed to have the properties of air at room temperature) enter a gas turbine at 1 MPa and 1500 K at a rate of 0.1 kg/s, and exit at 0.2 MPa and 900 K. If heat is lost from the turbine to the surroundings at a rate of 15 kJ/s, the power output of the gas turbine is (a) 15 Kw ________________ (b) 30 kW ________________ (c) 45kW ________________ (d )60kW ________________ (e) 75 kW

Problem 198P In a heating system, cold outdoor air at 7°C flowing at a rate of 4 kg/min is mixed adiabatically with heated air at 70°C flowing at a rate of 3 kg/min. The exit temperature of the mixture is (a) 34°C ________________ (b) 39°C ________________ (C) 45°C ________________ (d) 63°C ________________ (e) 77°C

Refrigerant-\(134a\) expands in an adiabatic turbine from \(1.2 \mathrm{MPa}\) and \(100^{\circ} \mathrm{C}\) to \(0.18 \mathrm{MPa}\) and \(50^{\circ} \mathrm{C}\) at a rate of \(1.25 \mathrm{~kg} / \mathrm{s}\). The power output of the turbine is (a) \(44.7 \mathrm{~kW}\) (b) \(66.4 \mathrm{~kW}\) (c) \(72.7 \mathrm{~kW}\) (d) \(89.2 \mathrm{~kW}\) (e) \(112.0 \mathrm{~kW}\) Equation Transcription: 100°C 50°C Text Transcription: 134a 1.2 MPa 100 degree celsius 0.18 MPa 50 degree celsius 1.25 kg/s 44.7 kW 66.4 kW 72.7 kW 89.2 kW

Problem 200P Steam expands in a turbine from 4 MPa and 500°C to 0.5 MPa and 250°C at a rate of 1350 kg/h. Heat is lost from the turbine at a rate of 25 kJ/s during the process. The power output of the turbine is (a) 157 kW ________________ (b) 207 kW ________________ (c) 182 kW ________________ (d) 287 kW ________________ (e) 246 kW

Problem 201P Steam is compressed by an adiabatic compressor from 0.2 MPa and 150°C to 0.8 MPa and 350°C at a rate of 1.30 kg/s. The power input to the compressor is (a) 511kW ________________ (b) 393 kW ________________ (c) 302kW ________________ (d) 717kW ________________ (e) 901kW

Problem 202P Refrigerant-134a is compressed by a compressor from the saturated vapor state at 0.14 MPa to 0.9 MPa and 60°C at a rate of 0.108 kg/s. The refrigerant is cooled at a rate of 1.10 kJ/s during compression. The power input to the compressor is. (a) 4.94kW ________________ (b) 6.04 kW ________________ (c) 7.14kW ________________ (d) 7.50 kW ________________ (e) 8.13 kW

Problem 205P Air at 27°C and 5 atm is throttled by a valve to 1 atm.If the valve is adiabatic and the change in kinetic energy is negligible, the exit temperature of air will be (a) 10ºC ________________ (b) 15ºC ________________ (c) 20°C ________________ (d) 23°C ________________ (e) 27°C

Problem 204P Refrigerant-134a at 1.4 MPa and 90°C is throttled to a pressure of 0.6 MPa. The temperature of the refrigerant after throttling is (a) 22°C ________________ (b) 56°C ________________ (c) 82°C ________________ (d) 80°C ________________ (e) 90°C

Problem 206P Steam at 1 MPa and 300°C is throttled adiabatically to a pressure of 0.4 MPa. If the change in kinetic energy is negligible, the specific volume of the steam after throttling is (a) 0.358 m3/kg ________________ (b) 0.233 m3/kg ________________ (c) 0.375 rnVkg ________________ (d) 0.646 m3/kg ________________ (e) 0.655 m3/kg

Refrigerant-134a enters the condenser of a refrigerator at \(900 \mathrm{kPa}\) and \(60^{\circ} \mathrm{C}\), and leaves as a saturated liquid at the same pressure. Determine the heat transfer from the refrigerant per unit mass. Equation Transcription: Text Transcription: 900 kPa 60 ^circC

Problem 5.51C Carbon dioxide enters an adiabatic compressor at and at a rate of and leaves at and . Neglect energy changes, determine (a) the volume flow rate of the carbon dioxide at the compressor inlet and (b) the power input to the compressor.

Problem 5.52 Air is compressed from and to a pressure of while being cooled at a rate of by circulating water through the compressor casing. The volume flow rate of the air at the inlet conditions is , and the power input to the compressor is . Determine (a) the mass flow rate of the air and (b) the temperature at the compressor exit.

Does the amount of mass entering a control volume have to be equal to the amount of mass leaving during an unsteady-flow process?

An adiabatic gas turbine expands air at and to and . Air enters the turbine through a opening with an average velocity of , and exhausts through a opening. Determine (a) the mass flow rate of air through the turbine and (b) the power produced by the turbine.

Steam enters a steady-flow turbine with a mass flow rate of at , , and a negligible velocity. The steam expands in the turbine to a saturated vapor at where 10 percent of the steam is removed for some other use. The remainder of the steam continues to expand to the turbine exit where the pressure is 10 kPa and quality is 85 percent. If the turbine is adiabatic, determine the rate of work done by the steam during this process.

Steam flows steadily into a turbine with a mass flow rate of and a negligible velocity at and . The steam leaves the turbine at and with a velocity of . The rate of work done by the steam in the turbine is measured to be . If the elevation change between the turbine inlet and exit is negligible, determine the rate of heat transfer associated with this process.

Air enters the compressor of a gas-turbine plant at ambient conditions of and with a low velocity and exits at and with a velocity of . The compressor is cooled at a rate of , and the power input to the compressor is . Determine the mass flow rate of air through the compressor

Why are throttling devices commonly used in refrigeration and air-conditioning applications?

A 2-m3 rigid tank initially contains air whose density is 1.18 kg/m3 . The tank is connected to a high-pressure supply line through a valve. The valve is opened, and air is allowed to enter the tank until the density in the tank rises to 5.30 kg/m3 . Determine the mass of air that has entered the tank.

A cyclone separator like that in Fig. P5-10 is used to remove fine solid particles, such as fly ash, that are suspended in a gas stream. In the flue-gas system of an electrical power plant, the weight fraction of fly ash in the exhaust gases is approximately 0.001. Determine the mass flow rates at the two outlets (flue gas and fly ash) when flue gas and ash mixture enters this unit. Also determine the amount of fly ash collected per year.

A spherical hot-air balloon is initially filled with air at and with an initial diameter of . Air enters this balloon at and with a velocity of through a 1-m diameter opening. How many minutes will it take to inflate this balloon to a 15-m diameter when the pressure and temperature of the air in the balloon remain the same as the air entering the balloon?

A desktop computer is to be cooled by a fan whose flow rate is . Determine the mass flow rate of air through the fan at an elevation of 3400 m where the air density is . Also, if the average velocity of air is not to exceed , determine the diameter of the casing of the fan.

A pump increases the water pressure from at the inlet to at the outlet. Water enters this pump at through a 1-cm-diameter opening and exits through a 1.5-cm-diameter opening. Determine the velocity of the water at the inlet and outlet when the mass flow rate through the pump is . Will these velocities change significantly if the inlet temperature is raised to ?

Refrigerant-134a enters a 28-cm-diameter pipe steadily at and with a velocity of . The refrigerant gains heat as it flows and leaves the pipe at and . Determine (a) the volume flow rate of the refrigerant at the inlet, (b) the mass flow rate of the refrigerant, and (c) the velocity and volume flow rate at the exit.

A smoking lounge is to accommodate 15 heavy smokers. The minimum fresh air requirement for smoking lounges is specified to be per person (ASHRAE, Standard 62, 1989). Determine the minimum required flow rate of fresh air that needs to be supplied to the lounge, and the diameter of the duct if the air velocity is not to exceed .

Consider a 300-L storage tank of a solar water heating system initially filled with warm water at . Warm water is withdrawn from the tank through a 2-cm diameter hose at an average velocity of while cold water enters the tank at at a rate of . Determine the amount of water in the tank after a 20-minute period. Assume the pressure in the tank remains constant at .

What is flow energy? Do fluids at rest possess any flow energy?

How do the energies of a flowing fluid and a fluid at rest compare? Name the specific forms of energy associated with each case.

A house is maintained at and , and warm air inside a house is forced to leave the house at a rate of as a result of outdoor air at infiltrating into the house through the cracks. Determine the rate of net energy loss of the house due to mass transfer.

A water pump increases the water pressure from to . Determine the flow work, in , required by the pump.

Refrigerant-134a enters the compressor of a refrigeration system as saturated vapor at , and leaves as superheated vapor at and at a rate of .Determine (a) the mass flow rate of the steam and the exit velocity, (b) the total and flow energies of the steam per unit mass, and (c) the rate at which energy is leaving the cooker by steam.

Steam is leaving a pressure cooker whose operating pressure is . It is observed that the amount of liquid in the cooker has decreased by in 45 minutes after the steady operating conditions are established, and the cross-sectional area of the exit opening is . Determine (a) the mass flow rate of the steam and the exit velocity, (b) the total and flow energies of the steam per unit mass, and (c) the rate at which energy is leaving the cooker by steam.

A diffuser is an adiabatic device that decreases the kinetic energy of the fluid by slowing it down. What happens to this lost kinetic energy?

The kinetic energy of a fluid increases as it is accelerated in an adiabatic nozzle. Where does this energy come from?

Is heat transfer to or from the fluid desirable as it flows through a nozzle? How will heat transfer affect the fluid velocity at the nozzle exit?

Air enters a nozzle steadily at 50 psia, 1408F, and 150 ft/s and leaves at 14.7 psia and 900 ft/s. The heat loss from the nozzle is estimated to be 6.5 Btu/lbm of air flowing. The inlet area of the nozzle is 0.1 ft2 . Determine (a) the exit temperature of air and (b) the exit area of the nozzle.

The stators in a gas turbine are designed to increase the kinetic energy of the gas passing through them adiabatically. Air enters a set of these nozzles at 300 psia and 7008F with a velocity of 80 ft/s and exits at 250 psia and 6458F. Calculate the velocity at the exit of the nozzles.

The diffuser in a jet engine is designed to decrease the kinetic energy of the air entering the engine compressor without any work or heat interactions. Calculate the velocity at the exit of a diffuser when air at 100 kPa and 308C enters it with a velocity of 350 m/s and the exit state is 200 kPa and 908C.

Air at 600 kPa and 500 K enters an adiabatic nozzle that has an inlet-to-exit area ratio of 2:1 with a velocity of 120 m/s and leaves with a velocity of 380 m/s. Determine (a) the exit temperature and (b) the exit pressure of the air.

Steam enters a nozzle at 4008C and 800 kPa with a velocity of 10 m/s, and leaves at 3008C and 200 kPa while losing heat at a rate of 25 kW. For an inlet area of 800 cm2 , determine the velocity and the volume flow rate of the steam at the nozzle exit.

Steam at 3 MPa and 4008C enters an adiabatic nozzle steadily with a velocity of 40 m/s and leaves at 2.5 MPa and 300 m/s. Determine (a) the exit temperature and (b) the ratio of the inlet to exit area A1/A2

Air at 13 psia and 658F enters an adiabatic diffuser steadily with a velocity of 750 ft/s and leaves with a low velocity at a pressure of 14.5 psia. The exit area of the diffuser is 3 times the inlet area. Determine (a) the exit temperature and (b) the exit velocity of the air.

Carbon dioxide enters an adiabatic nozzle steadily at 1 MPa and 5008C with a mass flow rate of 6000 kg/h and leaves at 100 kPa and 450 m/s. The inlet area of the nozzle is 40 cm2 . Determine (a) the inlet velocity and (b) the exit temperature.

Refrigerant-134a at 700 kPa and 1208C enters an adiabatic nozzle steadily with a velocity of 20 m/s and leaves at 400 kPa and 308C. Determine (a) the exit velocity and (b) the ratio of the inlet to exit area A1/A2.

Nitrogen gas at 60 kPa and 78C enters an adiabatic diffuser steadily with a velocity of 275 m/s and leaves at 85 kPa and 278C. Determine (a) the exit velocity of the nitrogen and (b) the ratio of the inlet to exit area A1/A2.

Reconsider Prob. 535. Using EES (or other) software, investigate the effect of the inlet velocity on the exit velocity and the ratio of the inlet-to-exit area. Let the inlet velocity vary from 210 to 350 m/s. Plot the final results against the inlet velocity, and discuss the results.

Refrigerant-134a enters a diffuser steadily as saturated vapor at 600 kPa with a velocity of 160 m/s, and it leaves at 700 kPa and 408C. The refrigerant is gaining heat at a rate of 2 kJ/s as it passes through the diffuser. If the exit area is 80 percent greater than the inlet area, determine (a) the exit velocity and (b) the mass flow rate of the refrigerant.

Steam at 4 MPa and 4008C enters a nozzle steadily with a velocity of 60 m/s, and it leaves at 2 MPa and 3008C. The inlet area of the nozzle is 50 cm2 , and heat is being lost at a rate of 75 kJ/s. Determine (a) the mass flow rate of the steam, (b) the exit velocity of the steam, and (c) the exit area of the nozzle.

Air at 80 kPa, 278C, and 220 m/s enters a diffuser at a rate of 2.5 kg/s and leaves at 428C. The exit area of the diffuser is 400 cm2 . The air is estimated to lose heat at a rate of 18 kJ/s during this process. Determine (a) the exit velocity and (b) the exit pressure of the air.

Consider an air compressor operating steadily. How would you compare the volume flow rates of the air at the compressor inlet and exit?

Will the temperature of air rise as it is compressed by an adiabatic compressor? Why?

Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold air leaving the turbine into the house. From a thermodynamic point of view, is the proposed system sound?

Air flows steadily through an adiabatic turbine, entering at 150 psia, 9008F, and 350 ft/s and leaving at 20 psia, 3008F, and 700 ft/s. The inlet area of the turbine is 0.1 ft2 . Determine (a) the mass flow rate of the air and (b) the power output of the turbine.

Refrigerant-134a enters an adiabatic compressor as saturated vapor at 2248C and leaves at 0.8 MPa and 608C. The mass flow rate of the refrigerant is 1.2 kg/s. Determine (a) the power input to the compressor and (b) the volume flow rate of the refrigerant at the compressor inlet.

Refrigerant-134a enters a compressor at 180 kPa as a saturated vapor with a flow rate of 0.35 m3 /min and leaves at 700 kPa. The power supplied to the refrigerant during compression process is 2.35 kW. What is the temperature of R-134a at the exit of the compressor?

Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are 4 MPa, 5008C, and 80 m/s, and the exit conditions are 30 kPa, 92 percent quality, and 50 m/s. The mass flow rate of the steam is 12 kg/s. Determine (a) the change in kinetic energy, (b) the power output, and (c) the turbine inlet area.

Reconsider Prob. 546. Using EES (or other) software, investigate the effect of the turbine exit pressure on the power output of the turbine. Let the exit pressure vary from 10 to 200 kPa. Plot the power output against the exit pressure, and discuss the results.

Steam enters an adiabatic turbine at 10 MPa and 5008C and leaves at 10 kPa with a quality of 90 percent. Neglecting the changes in kinetic and potential energies, determine the mass flow rate required for a power output of 5 MW.

Steam flows steadily through a turbine at a rate of 45,000 lbm/h, entering at 1000 psia and 9008F and leaving at 5 psia as saturated vapor. If the power generated by the turbine is 4 MW, determine the rate of heat loss from the steam.

Helium is to be compressed from 105 kPa and 295 K to 700 kPa and 460 K. A heat loss of 15 kJ/kg occurs during the compression process. Neglecting kinetic energy changes, determine the power input required for a mass flow rate of 60 kg/min.

Carbon dioxide enters an adiabatic compressor at 100 kPa and 300 K at a rate of 0.5 kg/s and leaves at 600 kPa and 450 K. Neglecting kinetic energy changes, determine (a) the volume flow rate of the carbon dioxide at the compressor inlet and (b) the power input to the compressor.

Air is compressed from 14.7 psia and 608F to a pressure of 150 psia while being cooled at a rate of 10 Btu/lbm by circulating water through the compressor casing. The volume flow rate of the air at the inlet conditions is 5000 ft3 /min, and the power input to the compressor is 700 hp. Determine (a) the mass flow rate of the air and (b) the temperature at the compressor exit.

Reconsider Prob. 552E. Using EES (or other) software, investigate the effect of the rate of cooling of the compressor on the exit temperature of air. Let the cooling rate vary from 0 to 100 Btu/lbm. Plot the air exit temperature against the rate of cooling, and discuss the results.

An adiabatic gas turbine expands air at 1300 kPa and 5008C to 100 kPa and 1278C. Air enters the turbine through a 0.2-m2 opening with an average velocity of 40 m/s, and exhausts through a 1-m2 opening. Determine (a) the mass flow rate of air through the turbine and (b) the power produced by the turbine.

Steam enters a steady-flow turbine with a mass flow rate of 13 kg/s at 6008C, 8 MPa, and a negligible velocity. The steam expands in the turbine to a saturated vapor at 300 kPa where 10 percent of the steam is removed for some other use. The remainder of the steam continues to expand to the turbine exit where the pressure is 10 kPa and quality is 85 percent. If the turbine is adiabatic, determine the rate of work done by the steam during this process.

Steam flows steadily into a turbine with a mass flow rate of 26 kg/s and a negligible velocity at 6 MPa and 6008C. The steam leaves the turbine at 0.5 MPa and 2008C with a velocity of 180 m/s. The rate of work done by the steam in the turbine is measured to be 20 MW. If the elevation change between the turbine inlet and exit is negligible, determine the rate of heat transfer associated with this process.

Air enters the compressor of a gas-turbine plant at ambient conditions of 100 kPa and 258C with a low velocity and exits at 1 MPa and 3478C with a velocity of 90 m/s. The compressor is cooled at a rate of 1500 kJ/min, and the power input to the compressor is 250 kW. Determine the mass flow rate of air through the compressor.

Why are throttling devices commonly used in refrigeration and air-conditioning applications?

Would you expect the temperature of air to drop as it undergoes a steady-flow throttling process? Explain.

Would you expect the temperature of a liquid to change as it is throttled? Explain.

During a throttling process, the temperature of a fluid drops from 30 to 2208C. Can this process occur adiabatically?

Refrigerant-134a is throttled from the saturated liquid state at 700 kPa to a pressure of 160 kPa. Determine the temperature drop during this process and the final specific volume of the refrigerant.

Saturated liquid-vapor mixture of water, called wet steam, in a steam line at 1500 kPa is throttled to 50 kPa and 1008C. What is the quality in the steam line?

Refrigerant-134a at 800 kPa and 258C is throttled to a temperature of 2208C. Determine the pressure and the internal energy of the refrigerant at the final state.

A well-insulated valve is used to throttle steam from 8 MPa and 3508C to 2 MPa. Determine the final temperature of the steam.

Reconsider Prob. 565. Using EES (or other) software, investigate the effect of the exit pressure of steam on the exit temperature after throttling. Let the exit pressure vary from 6 to 1 MPa. Plot the exit temperature of steam against the exit pressure, and discuss the results.

Refrigerant-134a enters the expansion valve of a refrigeration system at 120 psia as a saturated liquid and leaves at 20 psia. Determine the temperature and internal energy changes across the valve.

Consider a steady-flow mixing process. Under what conditions will the energy transported into the control volume by the incoming streams be equal to the energy transported out of it by the outgoing stream?

Consider a steady-flow heat exchanger involving two different fluid streams. Under what conditions will the amount of heat lost by one fluid be equal to the amount of heat gained by the other?

When two fluid streams are mixed in a mixing chamber, can the mixture temperature be lower than the temperature of both streams? Explain.

Liquid water at 300 kPa and 208C is heated in a chamber by mixing it with superheated steam at 300 kPa and 3008C. Cold water enters the chamber at a rate of 1.8 kg/s. If the mixture leaves the mixing chamber at 608C, determine the mass flow rate of the superheated steam required.

In steam power plants, open feedwater heaters are frequently utilized to heat the feedwater by mixing it with steam bled off the turbine at some intermediate stage. Consider an open feedwater heater that operates at a pressure of 1000 kPa. Feedwater at 508C and 1000 kPa is to be heated with superheated steam at 2008C and 1000 kPa. In an ideal feedwater heater, the mixture leaves the heater as saturated liquid at the feedwater pressure. Determine the ratio of the mass flow rates of the feedwater and the superheated vapor for this case.

Water at 658F and 20 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. If both streams enter the mixing chamber at the same mass flow rate, determine the temperature and the quality of the exiting stream.

A stream of refrigerant-134a at 1 MPa and 208C is mixed with another stream at 1 MPa and 808C. If the mass flow rate of the cold stream is twice that of the hot one, determine the temperature and the quality of the exit stream.

Reconsider Prob. 574. Using EES (or other) software, investigate the effect of the mass flow rate of the cold stream of R-134a on the temperature and the quality of the exit stream. Let the ratio of the mass flow rate of the cold stream to that of the hot stream vary from 1 to 4. Plot the mixture temperature and quality against the cold-tohot mass flow rate ratio, and discuss the results.

A heat exchanger is to heat water (cp 5 4.18 kJ/kg8C) from 25 to 608C at a rate of 0.2 kg/s. The heating is to be accomplished by geothermal water (cp 5 4.31 kJ/kg8C) available at 1408C at a mass flow rate of 0.3 kg/s. Determine the rate of heat transfer in the heat exchanger and the exit temperature of geothermal water.

Steam is to be condensed on the shell side of a heat exchanger at 758F. Cooling water enters the tubes at 508F at a rate of 45 lbm/s and leaves at 658F. Assuming the heat exchanger to be well-insulated, determine the rate of heat transfer in the heat exchanger and the rate of condensation of the steam.

A thin-walled double-pipe counter-flow heat exchanger is used to cool oil (cp 5 2.20 kJ/kg8C) from 150 to 408C at a rate of 2 kg/s by water (cp 5 4.18 kJ/kg8C) that enters at 228C at a rate of 1.5 kg/s. Determine the rate of heat transfer in the heat exchanger and the exit temperature of water.

Air (cp 5 1.005 kJ/kg8C) is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. Air enters the heat exchanger at 95 kPa and 208C at a rate of 0.6 m3 /s. The combustion gases (cp 5 1.10 kJ/kg8C) enter at 1608C at a rate of 0.95 kg/s and leave at 958C. Determine the rate of heat transfer to the air and its outlet temperature.

In a steam heating system, air is heated by being passed over some tubes through which steam flows steadily. Steam enters the heat exchanger at 30 psia and 4008F at a rate of 15 lbm/min and leaves at 25 psia and 2128F. Air enters at 14.7 psia and 808F and leaves at 1308F. Determine the volume flow rate of air at the inlet.

Refrigerant-134a at 1 MPa and 908C is to be cooled to 1 MPa and 308C in a condenser by air. The air enters at 100 kPa and 278C with a volume flow rate of 600 m3 /min and leaves at 95 kPa and 608C. Determine the mass flow rate of the refrigerant.

Air enters the evaporator section of a window air conditioner at 14.7 psia and 908F with a volume flow rate of 200 ft3 /min. Refrigerant-134a at 20 psia with a quality of 30 percent enters the evaporator at a rate of 4 lbm/min and leaves as saturated vapor at the same pressure. Determine (a) the exit temperature of the air and (b) the rate of heat transfer from the air.

An air-conditioning system involves the mixing of cold air and warm outdoor air before the mixture is routed to the conditioned room in steady operation. Cold air enters the mixing chamber at 78C and 105 kPa at a rate of 0.55 m3 /s while warm air enters at 348C and 105 kPa. The air leaves the room at 248C. The ratio of the mass flow rates of the hot to cold air streams is 1.6. Using variable specific heats, determine (a) the mixture temperature at the inlet of the room and (b) the rate of heat gain of the room.

Hot exhaust gases of an internal combustion engine are to be used to produce saturated water vapor at 2 MPa pressure. The exhaust gases enter the heat exchanger at 4008C at a rate of 32 kg/min while water enters at 158C. The heat exchanger is not well insulated, and it is estimated that 10 percent of heat given up by the exhaust gases is lost to the surroundings. If the mass flow rate of the exhaust gases is 15 times that of the water, determine (a) the temperature of the exhaust gases at the heat exchanger exit and (b) the rate of heat transfer to the water. Use the constant specific heat properties of air for the exhaust gases.

The evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at 200 kPa with a quality of 22 percent and a flow rate of 2.65 L/h. R-22 leaves the evaporator at the same pressure superheated by 58C. The refrigerant is evaporated by absorbing heat from air whose flow rate is 0.75 kg/s. Determine (a) the rate of heat absorbed from the air and (b) the temperature change of air. The properties of R-22 at the inlet and exit of the condenser are h1 5 220.2 kJ/kg, v1 5 0.0253 m3 /kg, and h2 5 398.0 kJ/kg.

Steam is to be condensed in the condenser of a steam power plant at a temperature of 508C with cooling water from a nearby lake, which enters the tubes of the condenser at 188C at a rate of 101 kg/s and leaves at 278C. Determine the rate of condensation of the steam in the condenser.

Reconsider Prob. 586. Using EES (or other) software, investigate the effect of the inlet temperature of cooling water on the rate of condensation of steam. Let the inlet temperature vary from 10 to 208C, and assume the exit temperature to remain constant. Plot the rate of condensation of steam against the inlet temperature of the cooling water, and discuss the results.

Two mass streams of the same ideal gas are mixed in a steady-flow chamber while receiving energy by heat transfer from the surroundings. The mixing process takes place at constant pressure with no work and negligible changes in kinetic and potential energies. Assume the gas has constant specific heats. (a) Determine the expression for the final temperature of the mixture in terms of the rate of heat transfer to the mixing chamber and the inlet and exit mass flow rates. (b) Obtain an expression for the volume flow rate at the exit of the mixing chamber in terms of the volume flow rates of the two inlet streams and the rate of heat transfer to the mixing chamber. (c) For the special case of adiabetic mixing, show that the exit volume flow rate is the sum of the two inlet volume flow rates.

Water enters a boiler at 500 psia as a saturated liquid and leaves at 6008F at the same pressure. Calculate the heat transfer per unit mass of water.

A 110-volt electrical heater is used to warm 0.3 m3 /s of air at 100 kPa and 158C to 100 kPa and 308C. How much current in amperes must be supplied to this heater?

The fan on a personal computer draws 0.3 ft3 /s of air at 14.7 psia and 708F through the box containing the CPU and other components. Air leaves at 14.7 psia and 838F. Calculate the electrical power, in kW, dissipated by the PC components.

Water enters the tubes of a cold plate at 708F with an average velocity of 40 ft/min and leaves at 1058F. The diameter of the tubes is 0.25 in. Assuming 15 percent of the heat generated is dissipated from the components to the surroundings by convection and radiation, and the remaining 85 percent is removed by the cooling water, determine the amount of heat generated by the electronic devices mounted on the cold plate.

A sealed electronic box is to be cooled by tap water flowing through the channels on two of its sides. It is specified that the temperature rise of the water not exceed 48C. The power dissipation of the box is 2 kW, which is removed entirely by water. If the box operates 24 hours a day, 365 days a year, determine the mass flow rate of water flowing through the box and the amount of cooling water used per year.

Repeat Prob. 593 for a power dissipation of 4 kW.

The components of an electronic system dissipating 180 W are located in a 1.4-m-long horizontal duct whose cross section is 20 cm 3 20 cm. The components in the duct are cooled by forced air that enters the duct at 308C and 1 atm at a rate of 0.6 m3 /min and leaves at 408C. Determine the rate of heat transfer from the outer surfaces of the duct to the ambient.

Repeat Prob. 595 for a circular horizontal duct of diameter 20 cm.

Consider a hollow-core printed circuit board 9 cm high and 18 cm long, dissipating a total of 15 W. The width of the air gap in the middle of the PCB is 0.25 cm. If the cooling air enters the 12-cm-wide core at 258C and 1 atm at a rate of 0.8 L/s, determine the average temperature at which the air leaves the hollow core.

A computer cooled by a fan contains eight PCBs, each dissipating 10 W power. The height of the PCBs is 12 cm and the length is 18 cm. The cooling air is supplied by a 25-W fan mounted at the inlet. If the temperature rise of air as it flows through the case of the computer is not to exceed 108C, determine (a) the flow rate of the air that the fan needs to deliver and (b) the fraction of the temperature rise of air that is due to the heat generated by the fan and its motor.

A 4-m 3 5-m 3 6-m room is to be heated by an electric resistance heater placed in a short duct in the room. Initially, the room is at 158C, and the local atmospheric pressure is 98 kPa. The room is losing heat steadily to the outside at a rate of 150 kJ/min. A 200-W fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of 40 kg/min. The duct can be assumed to be adiabatic, and there is no air leaking in or out of the room. If it takes 20 min for the room air to reach an average temperature of 258C, find (a) the power rating of the electric heater and (b) the temperature rise that the air experiences each time it passes through the heater.

A long roll of 2-m-wide and 0.5-cm-thick 1-Mn manganese steel plate (r 5 7854 kg/m3 and cp 5 0.434 kJ/kg8C) coming off a furnace at 8208C is to be quenched in an oil bath at 458C to a temperature of 51.18C. If the metal sheet is moving at a steady velocity of 10 m/min, determine the required rate of heat removal from the oil to keep its temperature constant at 458C.

Reconsider Prob. 5100. Using EES (or other) software, investigate the effect of the moving velocity of the steel plate on the rate of heat transfer from the oil bath. Let the velocity vary from 5 to 50 m/min. Plot the rate of heat transfer against the plate velocity, and discuss the results.

The hot-water needs of a household are to be met by heating water at 558F to 1808F by a parabolic solar collector at a rate of 4 lbm/s. Water flows through a 1.25-indiameter thin aluminum tube whose outer surface is blackanodized in order to maximize its solar absorption ability. The centerline of the tube coincides with the focal line of the collector, and a glass sleeve is placed outside the tube to minimize the heat losses. If solar energy is transferred to water at a net rate of 400 Btu/h per ft length of the tube, determine the required length of the parabolic collector to meet the hotwater requirements of this house.

A house has an electric heating system that consists of a 300-W fan and an electric resistance heating element placed in a duct. Air flows steadily through the duct at a rate of 0.6 kg/s and experiences a temperature rise of 78C. The rate of heat loss from the air in the duct is estimated to be 300 W. Determine the power rating of the electric resistance heating element.

Steam enters a long, horizontal pipe with an inlet diameter of D1 5 16 cm at 2 MPa and 3008C with a velocity of 2.5 m/s. Farther downstream, the conditions are 1.8 MPa and 2508C, and the diameter is D2 5 14 cm. Determine (a) the mass flow rate of the steam and (b) the rate of heat transfer

Refrigerant-134a enters the condenser of a refrigerator at 900 kPa and 608C, and leaves as a saturated liquid at the same pressure. Determine the heat transfer from the refrigerant per unit mass.

Saturated liquid water is heated at constant pressure in a steady-flow device until it is a saturated vapor. Calculate the heat transfer, in kJ/kg, when the vaporization is done at a pressure of 500 kPa

Water is heated in an insulated, constant-diameter tube by a 7-kW electric resistance heater. If the water enters the heater steadily at 208C and leaves at 758C, determine the mass flow rate of water.

Air at 300 K and 100 kPa steadily flows into a hair dryer having electrical work input of 1500 W. Because of the size of the air intake, the inlet velocity of the air is negligible. The air temperature and velocity at the hair dryer exit are 808C and 21 m/s, respectively. The flow process is both constant pressure and adiabatic. Assume air has constant specific heats evaluated at 300 K. (a) Determine the air mass flow rate into the hair dryer, in kg/s. (b) Determine the air volume flow rate at the hair dryer exit, in m3 /s.

Reconsider Prob. 5108. Using EES (or other) software, investigate the effect of the exit velocity on the mass flow rate and the exit volume flow rate. Let the exit velocity vary from 5 to 25 m/s. Plot the mass flow rate and exit volume flow rate against the exit velocity, and discuss the results

Air enters the duct of an air-conditioning system at 15 psia and 508F at a volume flow rate of 450 ft3 /min. The diameter of the duct is 10 in, and heat is transferred to the air in the duct from the surroundings at a rate of 2 Btu/s. Determine (a) the velocity of the air at the duct inlet and (b) the temperature of the air at the exit.

A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries steam at 4 MPa. Now the valve is opened, and steam is allowed to flow into the tank until the pressure reaches 4 MPa, at which point the valve is closed. If the final temperature of the steam in the tank is 5508C, determine the temperature of the steam in the supply line and the flow work per unit mass of the steam.

A 2-m3 rigid insulated tank initially containing saturated water vapor at 1 MPa is connected through a valve to a supply line that carries steam at 4008C. Now the valve is opened, and steam is allowed to flow slowly into the tank until the pressure in the tank rises to 2 MPa. At this instant the tank temperature is measured to be 3008C. Determine the mass of the steam that has entered and the pressure of the steam in the supply line.

A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries helium at 200 kPa and 1208C. Now the valve is opened, and helium is allowed to flow into the tank until the pressure reaches 200 kPa, at which point the valve is closed. Determine the flow work of the helium in the supply line and the final temperature of the helium in the tank.

Consider a 35-L evacuated rigid bottle that is surrounded by the atmosphere at 100 kPa and 228C. A valve at the neck of the bottle is now opened and the atmospheric air is allowed to flow into the bottle. The air trapped in the bottle eventually reaches thermal equilibrium with the atmosphere as a result of heat transfer through the wall of the bottle. The valve remains open during the process so that the trapped air also reaches mechanical equilibrium with the atmosphere. Determine the net heat transfer through the wall of the bottle during this filling process.

A 0.2-m3 rigid tank equipped with a pressure regulator contains steam at 2 MPa and 3008C. The steam in the tank is now heated. The regulator keeps the steam pressure constant by letting out some steam, but the temperature inside rises. Determine the amount of heat transferred when the steam temperature reaches 5008C.

A 3-ft3 rigid tank initially contains saturated water vapor at 3008F. The tank is connected by a valve to a supply line that carries steam at 200 psia and 4008F. Now the valve is opened, and steam is allowed to enter the tank. Heat transfer takes place with the surroundings such that the temperature in the tank remains constant at 3008F at all times. The valve is closed when it is observed that one-half of the volume of the tank is occupied by liquid water. Find (a) the final pressure in the tank, (b) the amount of steam that has entered the tank, and (c) the amount of heat transfer.

A 4-L pressure cooker has an operating pressure of 175 kPa. Initially, one-half of the volume is filled with liquid and the other half with vapor. If it is desired that the pressure cooker not run out of liquid water for 1 h, determine the highest rate of heat transfer allowed.

An insulated, vertical pistoncylinder device initially contains 10 kg of water, 6 kg of which is in the vapor phase. The mass of the piston is such that it maintains a constant pressure of 200 kPa inside the cylinder. Now steam at 0.5 MPa and 3508C is allowed to enter the cylinder from a supply line until all the liquid in the cylinder has vaporized. Determine (a) the final temperature in the cylinder and (b) the mass of the steam that has entered.

A scuba divers 2-ft3 air tank is to be filled with air from a compressed air line at 120 psia and 858F. Initially, the air in this tank is at 20 psia and 608F. Presuming that the tank is well insulated, determine the temperature and mass in the tank when it is filled to 120 psia.

An air-conditioning system is to be filled from a rigid container that initially contains 5 kg of liquid R-134a at 248C. The valve connecting this container to the air-conditioning system is now opened until the mass in the container is 0.25 kg, at which time the valve is closed. During this time, only liquid R-134a flows from the container. Presuming that the process is isothermal while the valve is open, determine the final quality of the R-134a in the container and the total heat transfer.

Oxygen is supplied to a medical facility from ten 1.5-ft3 compressed oxygen tanks. Initially, these tanks are at 1500 psia and 808F. The oxygen is removed from these tanks slowly enough that the temperature in the tanks remains at 808F. After two weeks, the pressure in the tanks is 300 psia. Determine the mass of oxygen used and the total heat transfer to the tanks.

A 0.06-m3 rigid tank initially contains refrigerant-134a at 0.8 MPa and 100 percent quality. The tank is connected by a valve to a supply line that carries refrigerant-134a at 1.2 MPa and 368C. Now the valve is opened, and the refrigerant is allowed to enter the tank. The valve is closed when it is observed that the tank contains saturated liquid at 1.2 MPa. Determine (a) the mass of the refrigerant that has entered the tank and (b) the amount of heat transfer.

A 0.3-m3 rigid tank is filled with saturated liquid water at 2008C. A valve at the bottom of the tank is opened, and liquid is withdrawn from the tank. Heat is transferred to the water such that the temperature in the tank remains constant. Determine the amount of heat that must be transferred by the time one-half of the total mass has been withdrawn.

A 2-ft3 rigid tank contains saturated refrigerant- 134a at 160 psia. Initially, 5 percent of the volume is occupied by liquid and the rest by vapor. A valve at the top of the tank is now opened, and vapor is allowed to escape slowly from the tank. Heat is transferred to the refrigerant such that the pressure inside the tank remains constant. The valve is closed when the last drop of liquid in the tank is vaporized. Determine the total heat transfer for this process

A 0.3-m3 rigid tank initially contains refrigerant- 134a at 148C. At this state, 55 percent of the mass is in the vapor phase, and the rest is in the liquid phase. The tank is connected by a valve to a supply line where refrigerant at 1.4 MPa and 1008C flows steadily. Now the valve is opened slightly, and the refrigerant is allowed to enter the tank. When the pressure in the tank reaches 1 MPa, the entire refrigerant in the tank exists in the vapor phase only. At this point the valve is closed. Determine (a) the final temperature in the tank, (b) the mass of refrigerant that has entered the tank, and (c) the heat transfer between the system and the surroundings.

A balloon that initially contains 50 m3 of steam at 100 kPa and 1508C is connected by a valve to a large reservoir that supplies steam at 150 kPa and 2008C. Now the valve is opened, and steam is allowed to enter the balloon until the pressure equilibrium with the steam at the supply line is reached. The material of the balloon is such that its volume increases linearly with pressure. Heat transfer also takes place between the balloon and the surroundings, and the mass of the steam in the balloon doubles at the end of the process. Determine the final temperature and the boundary work during this process.

The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of 0.5 m2 , and the filling opening has an area of 1 m2 . During a two minute adiabatic flight maneuver, hot air enters the balloon at 100 kPa and 358C with a velocity of 2 m/s; the air in the balloon remains at 100 kPa and 358C; and air leaves the balloon through the air-release flap at velocity 1 m/s. At the start of this maneuver, the volume of the balloon is 75 m3 . Determine the final volume of the balloon and work produced by the air inside the balloon as it expands the balloon skin.

An insulated 0.15-m3 tank contains helium at 3 MPa and 1308C. A valve is now opened, allowing some helium to escape. The valve is closed when one-half of the initial mass has escaped. Determine the final temperature and pressure in the tank.

An insulated 40-ft3 rigid tank contains air at 50 psia and 1208F. A valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. The air temperature during this process is maintained constant by an electric resistance heater placed in the tank. Determine the electrical work done during this process.

A vertical pistoncylinder device initially contains 0.2 m3 of air at 208C. The mass of the piston is such that it maintains a constant pressure of 300 kPa inside. Now a valve connected to the cylinder is opened, and air is allowed to escape until the volume inside the cylinder is decreased by one-half. Heat transfer takes place during the process so that the temperature of the air in the cylinder remains constant. Determine (a) the amount of air that has left the cylinder and (b) the amount of heat transfer.

A vertical pistoncylinder device initially contains 0.25 m3 of air at 600 kPa and 3008C. A valve connected to the cylinder is now opened, and air is allowed to escape until three-quarters of the mass leave the cylinder at which point the volume is 0.05 m3 . Determine the final temperature in the cylinder and the boundary work during this process.

A vertical pistoncylinder device initially contains 0.01 m3 of steam at 2008C. The mass of the frictionless piston is such that it maintains a constant pressure of 500 kPa inside. Now steam at 1 MPa and 3508C is allowed to enter the cylinder from a supply line until the volume inside doubles. Neglecting any heat transfer that may have taken place during the process, determine (a) the final temperature of the steam in the cylinder and (b) the amount of mass that has entered.

The air in an insulated, rigid compressed-air tank whose volume is 0.5 m3 is initially at 4000 kPa and 208C. Enough air is now released from the tank to reduce the pressure to 2000 kPa. Following this release, what is the temperature of the remaining air in the tank?

An insulated vertical pistoncylinder device initially contains 0.8 m3 of refrigerant-134a at 1.4 MPa and 1208C. A linear spring at this point applies full force to the piston. A valve connected to the cylinder is now opened, and refrigerant is allowed to escape. The spring unwinds as the piston moves down, and the pressure and volume drop to 0.7 MPa and 0.5 m3 at the end of the process. Determine (a) the amount of refrigerant that has escaped and (b) the final temperature of the refrigerant

The air in a 6-m 3 5-m 3 4-m hospital room is to be completely replaced by conditioned air every 15 min. If the average air velocity in the circular air duct leading to the room is not to exceed 5 m/s, determine the minimum diameter of the duct.

A long roll of 1-m-wide and 0.5-cm-thick 1-Mn manganese steel plate (r 5 7854 kg/m3 ) coming off a furnace is to be quenched in an oil bath to a specified temperature. If the metal sheet is moving at a steady velocity of 10 m/min, determine the mass flow rate of the steel plate through the oil bath.

Air at 4.18 kg/m3 enters a nozzle that has an inletto-exit area ratio of 2:1 with a velocity of 120 m/s and leaves with a velocity of 380 m/s. Determine the density of air at the exit.

An air compressor compresses 15 L/s of air at 120 kPa and 208C to 800 kPa and 3008C while consuming 6.2 kW of power. How much of this power is being used to increase the pressure of the air versus the power needed to move the fluid through the compressor?

Saturated refrigerant-134a vapor at 348C is to be condensed as it flows in a 1-cm-diameter tube at a rate of 0.1 kg/min. Determine the rate of heat transfer from the refrigerant. What would your answer be if the condensed refrigerant is cooled to 208C?

A steam turbine operates with 1.6 MPa and 3508C steam at its inlet and saturated vapor at 308C at its exit. The mass flow rate of the steam is 22 kg/s, and the turbine produces 12,350 kW of power. Determine the rate at which heat is lost through the casing of this turbine.

Nitrogen gas flows through a long, constant-diameter adiabatic pipe. It enters at 100 psia and 1208F and leaves at 50 psia and 708F. Calculate the velocity of the nitrogen at the pipes inlet and outlet.

A 110-V electric hot-water heater warms 0.1 L/s of water from 18 to 308C. Calculate the current in amperes that must be supplied to this heater.

Steam enters a long, insulated pipe at 1200 kPa, 2508C, and 4 m/s, and exits at 1000 kPa. The diameter of the pipe is 0.15 m at the inlet, and 0.1 m at the exit. Calculate the mass flow rate of the steam and its speed at the pipe outlet.

Air enters a pipe at 658C and 200 kPa and leaves at 608C and 175 kPa. It is estimated that heat is lost from the pipe in the amount of 3.3 kJ per kg of air flowing in the pipe. The diameter ratio for the pipe is D1/D2 5 1.4. Using constant specific heats for air, determine the inlet and exit velocities of the air.

Steam enters a nozzle with a low velocity at 1508C and 200 kPa, and leaves as a saturated vapor at 75 kPa. There is a heat transfer from the nozzle to the surroundings in the amount of 26 kJ for every kilogram of steam flowing through the nozzle. Determine (a) the exit velocity of the steam and (b) the mass flow rate of the steam at the nozzle entrance if the nozzle exit area is 0.001 m2 .

In a gas-fired boiler, water is boiled at 1808C by hot gases flowing through a stainless steel pipe submerged in water. If the rate of heat transfer from the hot gases to water is 48 kJ/s, determine the rate of evaporation of water.

Saturated steam at 1 atm condenses on a vertical plate that is maintained at 908C by circulating cooling water through the other side. If the rate of heat transfer by condensation to the plate is 180 kJ/s, determine the rate at which the condensate drips off the plate at the bottom.

The condenser of a steam power plant operates at a pressure of 0.95 psia. The condenser consists of 144 horizontal tubes arranged in a 12 3 12 square array. Steam condenses on the outer surfaces of the tubes whose inner and outer diameters are 1 in and 1.2 in, respectively. If steam is to be condensed at a rate of 6800 lbm/h and the temperature rise of the cooling water is limited to 88F, determine (a) the rate of heat transfer from the steam to the cooling water and (b) the average velocity of the cooling water through the tubes.

In large steam power plants, the feedwater is frequently heated in a closed feedwater heater by using steam extracted from the turbine at some stage. Steam enters the feedwater heater at 1 MPa and 2008C and leaves as saturated liquid at the same pressure. Feedwater enters the heater at 2.5 MPa and 508C and leaves at 108C below the exit temperature of the steam. Determine the ratio of the mass flow rates of the extracted steam and the feedwater.

Cold water enters a steam generator at 208C and leaves as saturated vapor at 2008C. Determine the fraction of heat used in the steam generator to preheat the liquid water from 208C to the saturation temperature of 2008C.

Cold water enters a steam generator at 208C and leaves as saturated vapor at the boiler pressure. At what pressure will the amount of heat needed to preheat the water to saturation temperature be equal to the heat needed to vaporize the liquid at the boiler pressure?

An ideal gas expands in an adiabatic turbine from 1200 K and 900 kPa to 800 K. Determine the turbine inlet volume flow rate of the gas, in m3 /s, required to produce turbine work output at the rate of 650 kW. The average values of the specific heats for this gas over the temperature range and the gas constant are cp 5 1.13 kJ/kgK, cv 5 0.83 kJ/kgK, and R 5 0.30 kJ/kgK.

Chickens with an average mass of 2.2 kg and average specific heat of 3.54 kJ/kg8C are to be cooled by chilled water that enters a continuous-flow-type immersion chiller at 0.58C. Chickens are dropped into the chiller at a uniform temperature of 158C at a rate of 500 chickens per hour and are cooled to an average temperature of 38C before they are taken out. The chiller gains heat from the surroundings at a rate of 200 kJ/h. Determine (a) the rate of heat removal from the chickens, in kW, and (b) the mass flow rate of water, in kg/s, if the temperature rise of water is not to exceed 28C.

Repeat Prob. 5153 assuming heat gain of the chiller is negligible.

A refrigeration system is being designed to cool eggs ( r 5 67.4 lbm/ft3 and cp 5 0.80 Btu/lbm8F) with an average mass of 0.14 lbm from an initial temperature of 908F to a final average temperature of 508F by air at 348F at a rate of 10,000 eggs per hour. Determine (a) the rate of heat removal from the eggs, in Btu/h and (b) the required volume flow rate of air, in ft3 /h, if the temperature rise of air is not to exceed 108F.

A glass bottle washing facility uses a well-agitated hot-water bath at 508C that is placed on the ground. The bottles enter at a rate of 450 per minute at an ambient temperature of 208C and leave at the water temperature. Each bottle has a mass of 150 g and removes 0.2 g of water as it leaves the bath wet. Make-up water is supplied at 158C. Disregarding any heat losses from the outer surfaces of the bath, determine the rate at which (a) water and (b) heat must be supplied to maintain steady operation.

The heat of hydration of dough, which is 15 kJ/kg, will raise its temperature to undesirable levels unless some cooling mechanism is utilized. A practical way of absorbing the heat of hydration is to use refrigerated water when kneading the dough. If a recipe calls for mixing 2 kg of flour with 1 kg of water, and the temperature of the city water is 158C, determine the temperature to which the city water must be cooled before mixing in order for the water to absorb the entire heat of hydration when the water temperature rises to 158C. Take the specific heats of the flour and the water to be 1.76 and 4.18 kJ/kg8C, respectively.

Long aluminum wires of diameter 5 mm (r 5 2702 kg/m3 and cp 5 0.896 kJ/kg8C) are extruded at a temperature of 3508C and are cooled to 508C in atmospheric air at 258C. If the wire is extruded at a velocity of 8 m/min, determine the rate of heat transfer from the wire to the extrusion room.

Repeat Prob. 5158 for a copper wire (r 5 8950 kg/m3 and cp 5 0.383 kJ/kg8C).

Steam at 80 psia and 4008F is mixed with water at 608F and 80 psia steadily in an adiabatic device. Steam enters the device at a rate of 0.05 lbm/s, while the water enters at 1 lbm/s. Determine the temperature of the mixture leaving this device when the outlet pressure is 80 psia.

A constant-pressure R-134a vapor separation unit separates the liquid and vapor portions of a saturated mixture into two separate outlet streams. Determine the flow power needed to pass 6 L/s of R-134a at 320 kPa and 55 percent quality through this unit. What is the mass flow rate, in kg/s, of the two outlet streams?

Consider two identical buildings: one in Los Angeles, California, where the atmospheric pressure is 101 kPa and the other in Denver, Colorado, where the atmospheric pressure is 83 kPa. Both buildings are maintained at 218C, and the infiltration rate for both buildings is 1.2 air changes per hour (ACH). That is, the entire air in the building is replaced completely by the outdoor air 1.2 times per hour on a day when the outdoor temperature at both locations is 108C. Disregarding latent heat, determine the ratio of the heat losses by infiltration at the two cities.

It is well established that indoor air quality (IAQ) has a significant effect on general health and productivity of employees at a workplace. A study showed that enhancing IAQ by increasing the building ventilation from 5 cfm (cubic feet per minute) to 20 cfm increased the productivity by 0.25 percent, valued at $90 per person per year, and decreased the respiratory illnesses by 10 percent for an average annual savings of $39 per person while increasing the annual energy consumption by $6 and the equipment cost by about $4 per person per year (ASHRAE Journal, December 1998). For a workplace with 120 employees, determine the net monetary benefit of installing an enhanced IAQ system to the employer per year.

The ventilating fan of the bathroom of a building has a volume flow rate of 30 L/s and runs continuously. The building is located in San Francisco, California, where the average winter temperature is 12.28C, and is maintained at 228C at all times. The building is heated by electricity whose unit cost is $0.12/kWh. Determine the amount and cost of the heat vented out per month in winter.

During the inflation and deflation of a safety airbag in an automobile, the gas enters the airbag with a specific volume of 15 ft3 /lbm and at a mass flow rate that varies with time as illustrated in Fig. P5165E. The gas leaves this airbag with a specific volume of 13 ft3 /lbm, with a mass flow rate that varies with time, as shown in Fig. P5165E. Plot the volume of this bag (i.e., airbag size) as a function of time, in ft3 .

Determine the rate of sensible heat loss from a building due to infiltration if the outdoor air at 258C and 95 kPa enters the building at a rate of 60 L/s when the indoors is maintained at 258C.

An air-conditioning system requires airflow at the main supply duct at a rate of 130 m3 /min. The average velocity of air in the circular duct is not to exceed 8 m/s to avoid excessive vibration and pressure drops. Assuming the fan converts 80 percent of the electrical energy it consumes into kinetic energy of air, determine the size of the electric motor needed to drive the fan and the diameter of the main duct. Take the density of air to be 1.20 kg/m3 .

The maximum flow rate of standard shower heads is about 3.5 gpm (13.3 L/min) and can be reduced to 2.75 gpm (10.5 L/min) by switching to low-flow shower heads that are equipped with flow controllers. Consider a family of four, with each person taking a 5-min shower every morning. City water at 158C is heated to 558C in an electric water heater and tempered to 428C by cold water at the T-elbow of the shower before being routed to the shower heads. Assuming a constant specific heat of 4.18 kJ/kg8C for water, determine (a) the ratio of the flow rates of the hot and cold water as they enter the T-elbow and (b) the amount of electricity that will be saved per year, in kWh, by replacing the standard shower heads by the low-flow ones.

Reconsider Prob. 5168. Using EES (or other) software, investigate the effect of the inlet temperature of cold water on the energy saved by using the lowflow shower head. Let the inlet temperature vary from 108C to 208C. Plot the electric energy savings against the water inlet temperature, and discuss the results.

An adiabatic air compressor is to be powered by a direct-coupled adiabatic steam turbine that is also driving a generator. Steam enters the turbine at 12.5 MPa and 5008C at a rate of 25 kg/s and exits at 10 kPa and a quality of 0.92. Air enters the compressor at 98 kPa and 295 K at a rate of 10 kg/s and exits at 1 MPa and 620 K. Determine the net power delivered to the generator by the turbine.

Determine the power input for a compressor that compresses helium from 110 kPa and 208C to 400 kPa and 2008C. Helium enters this compressor through a 0.1-m2 pipe at a velocity of 9 m/s.

Refrigerant 134a enters a compressor with a mass flow rate of 5 kg/s and a negligible velocity. The refrigerant enters the compressor as a saturated vapor at 108C and leaves the compressor at 1400 kPa with an enthalpy of 281.39 kJ/kg and a velocity of 50 m/s. The rate of work done on the refrigerant is measured to be 132.4 kW. If the elevation change between the compressor inlet and exit is negligible, determine the rate of heat transfer associated with this process, in kW.

Submarines change their depth by adding or removing air from rigid ballast tanks, thereby displacing seawater in the tanks. Consider a submarine that has a 700 m3 air-ballast tank originally partially filled with 100 m3 of air at 1500 kPa and 158C. For the submarine to surface, air at 1500 kPa and 208C is pumped into the ballast tank, until it is entirely filled with air. The tank is filled so quickly that the process is adiabatic and the seawater leaves the tank at 158C. Determine the final temperature and mass of the air in the ballast tank.

In Prob. 5-173, presume that air is added to the tank in such a way that the temperature and pressure of the air in the tank remain constant. Determine the final mass of the air in the ballast tank under this condition. Also determine the total heat transfer while the tank is being filled in this manner

Water flows through a shower head steadily at a rate of 10 L/min. An electric resistance heater placed in the water pipe heats the water from 16 to 438C. Taking the density of water to be 1 kg/L, determine the electric power input to the heater, in kW. In an effort to conserve energy, it is proposed to pass the drained warm water at a temperature of 398C through a heat exchanger to preheat the incoming cold water. If the heat exchanger has an effectiveness of 0.50 (that is, it recovers only half of the energy that can possibly be transferred from the drained water to incoming cold water), determine the electric power input required in this case. If the price of the electric energy is 11.5 /kWh, determine how much money is saved during a 10-min shower as a result of installing this heat exchanger.

Reconsider Prob. 5175. Using EES (or other) software, investigate the effect of the heat exchanger effectiveness on the money saved. Let effectiveness range from 20 to 90 percent. Plot the money saved against the effectiveness, and discuss the results.

A tank with an internal volume of 1 m3 contains air at 800 kPa and 258C. A valve on the tank is opened allowing air to escape and the pressure inside quickly drops to 150 kPa, at which point the valve is closed. Assume there is negligible heat transfer from the tank to the air left in the tank. (a) Using the approximation he < constant 5 he,avg 5 0.5(h1 1 h2), calculate the mass withdrawn during the process. (b) Consider the same process but broken into two parts. That is, consider an intermediate state at P2 5 400 kPa, calculate the mass removed during the process from P1 5 800 kPa to P2 and then the mass removed during the process from P2 to P3 5 150 kPa, using the type of approximation used in part (a), and add the two to get the total mass removed. (c) Calculate the mass removed if the variation of he is accounted for.

A liquid R-134a bottle has an internal volume of 0.0015 m3 . Initially it contains 0.55 kg of R-134a (saturated mixture) at 268C. A valve is opened and R-134a vapor only (no liquid) is allowed to escape slowly such that temperature remains constant until the mass of R-134a remaining is 0.15 kg. Find the heat transfer necessary with the surroundings to maintain the temperature and pressure of the R-134a constant.

Steam enters a turbine steadily at 7 MPa and 6008C with a velocity of 60 m/s and leaves at 25 kPa with a quality of 95 percent. A heat loss of 20 kJ/kg occurs during the process. The inlet area of the turbine is 150 cm2 , and the exit area is 1400 cm2 . Determine (a) the mass flow rate of the steam, (b) the exit velocity, and (c) the power output

Reconsider Prob. 5179. Using EES (or other) software, investigate the effects of turbine exit area and turbine exit pressure on the exit velocity and power output of the turbine. Let the exit pressure vary from 10 to 50 kPa (with the same quality), and the exit area to vary from 1000 to 3000 cm2 . Plot the exit velocity and the power outlet against the exit pressure for the exit areas of 1000, 2000, and 3000 cm2 , and discuss the results.

In large gas-turbine power plants, air is preheated by the exhaust gases in a heat exchanger called the regenerator before it enters the combustion chamber. Air enters the regenerator at 1 MPa and 550 K at a mass flow rate of 800 kg/min. Heat is transferred to the air at a rate of 3200 kJ/s. Exhaust gases enter the regenerator at 140 kPa and 800 K and leave at 130 kPa and 600 K. Treating the exhaust gases as air, determine (a) the exit temperature of the air and (b) the mass flow rate of exhaust gases.

It is proposed to have a water heater that consists of an insulated pipe of 7.5-cm diameter and an electric resistor inside. Cold water at 208C enters the heating section steadily at a rate of 24 L/min. If water is to be heated to 488C, determine (a) the power rating of the resistance heater and (b) the average velocity of the water in the pipe.

An insulated vertical pistoncylinder device initially contains 0.11 m3 of air at 150 kPa and 228C. At this state, a linear spring touches the piston but exerts no force on it. The cylinder is connected by a valve to a line that supplies air at 700 kPa and 228C. The valve is opened, and air from the high-pressure line is allowed to enter the cylinder. The valve is turned off when the pressure inside the cylinder reaches 600 kPa. If the enclosed volume inside the cylinder doubles during this process, determine (a) the mass of air that entered the cylinder, and (b) the final temperature of the air inside the cylinder.

A pistoncylinder device initially contains 2 kg of refrigerant-134a at 800 kPa and 808C. At this state, the piston is touching on a pair of stops at the top. The mass of the piston is such that a 500-kPa pressure is required to move it. A valve at the bottom of the tank is opened, and R-134a is withdrawn from the cylinder. After a while, the piston is observed to move and the valve is closed when half of the refrigerant is withdrawn from the tank and the temperature in the tank drops to 208C. Determine (a) the work done and (b) the heat transfer.

A pistoncylinder device initially contains 1.2 kg of air at 700 kPa and 2008C. At this state, the piston is touching on a pair of stops. The mass of the piston is such that 600-kPa pressure is required to move it. A valve at the bottom of the tank is opened, and air is withdrawn from the cylinder. The valve is closed when the volume of the cylinder decreases to 80 percent of the initial volume. If it is estimated that 40 kJ of heat is lost from the cylinder, determine (a) the final temperature of the air in the cylinder, (b) the amount of mass that has escaped from the cylinder, and (c) the work done. Use constant specific heats at the average temperature.

In a single-flash geothermal power plant, geothermal water enters the flash chamber (a throttling valve) at 2308C as a saturated liquid at a rate of 50 kg/s. The steam resulting from the flashing process enters a turbine and leaves at 20 kPa with a moisture content of 5 percent. Determine the temperature of the steam after the flashing process and the power output from the turbine if the pressure of the steam at the exit of the flash chamber is (a) 1 MPa, (b) 500 kPa, (c) 100 kPa, (d) 50 kPa.

The turbocharger of an internal combustion engine consists of a turbine and a compressor. Hot exhaust gases flow through the turbine to produce work and the work output from the turbine is used as the work input to the compressor. The pressure of ambient air is increased as it flows through the compressor before it enters the engine cylinders. Thus, the purpose of a turbocharger is to increase the pressure of air so that more air gets into the cylinder. Consequently, more fuel can be burned and more power can be produced by the engine. In a turbocharger, exhaust gases enter the turbine at 4008C and 120 kPa at a rate of 0.02 kg/s and leave at 3508C. Air enters the compressor at 508C and 100 kPa and leaves at 130 kPa at a rate of 0.018 kg/s. The compressor increases the air pressure with a side effect: It also increases the air temperature, which increases the possibility of a gasoline engine to experience an engine knock. To avoid this, an aftercooler is placed after the compressor to cool the warm air by cold ambient air before it enters the engine cylinders. It is estimated that the aftercooler must decrease the air temperature below 808C if knock is to be avoided. The cold ambient air enters the aftercooler at 308C and leaves at 408C. Disregarding any frictional losses in the turbine and the compressor and treating the exhaust gases as air, determine (a) the temperature of the air at the compressor outlet and (b) the minimum volume flow rate of ambient air required to avoid knock.

A building with an internal volume of 400 m3 is to be heated by a 30-kW electric resistance heater placed in the duct inside the building. Initially, the air in the building is at 148C, and the local atmospheric pressure is 95 kPa. The building is losing heat to the surroundings at a steady rate of 450 kJ/min. Air is forced to flow through the duct and the heater steadily by a 250-W fan, and it experiences a temperature rise of 58C each time it passes through the duct, which may be assumed to be adiabatic. (a) How long will it take for the air inside the building to reach an average temperature of 248C? (b) Determine the average mass flow rate of air through the duct.

A D0 5 10-m-diameter tank is initially filled with water 2 m above the center of a D 5 10-cm-diameter valve near the bottom. The tank surface is open to the atmosphere, and the tank drains through a L 5 100-m-long pipe connected to the valve. The friction factor of the pipe is given to be f 5 0.015, and the discharge velocity is expressed as V 5 2gz 1.5 1 fL/D where z is the water height above the center of the valve. Determine (a) the initial discharge velocity from the tank and (b) the time required to empty the tank. The tank can be considered to be empty when the water level drops to the center of the valve.

The velocity of a liquid flowing in a circular pipe of radius R varies from zero at the wall to a maximum at the pipe center. The velocity distribution in the pipe can be represented as V(r), where r is the radial distance from the pipe center. Based on the definition of mass flow rate m , obtain a relation for the average velocity in terms of V(r), R, and r.

Two streams of the same ideal gas having different mass flow rates and temperatures are mixed in a steady-flow, adiabatic mixing device. Assuming constant specific heats, find the simplest expression for the mixture temperature written in the form

Steam is compressed by an adiabatic compressor from 0.2 MPa and 1508C to 2.5 MPa and 2508C at a rate of 1.30 kg/s. The power input to the compressor is (a) 144 kW (b) 234 kW (c) 438 kW (d) 717 kW (e) 901 kW

Steam enters a diffuser steadily at 0.5 MPa, 3008C, and 122 m/s at a rate of 3.5 kg/s. The inlet area of the diffuser is (a) 15 cm2 (b) 50 cm2 (c) 105 cm2 (d) 150 cm2 (e) 190 cm2

An adiabatic heat exchanger is used to heat cold water at 158C entering at a rate of 5 kg/s by hot air at 908C entering also at a rate of 5 kg/s. If the exit temperature of hot air is 208C, the exit temperature of cold water is (a) 278C (b) 328C (c) 528C (d) 858C (e) 908C

A heat exchanger is used to heat cold water at 158C entering at a rate of 2 kg/s by hot air at 858C entering at a rate of 3 kg/s. The heat exchanger is not insulated and is losing heat at a rate of 25 kJ/s. If the exit temperature of hot air is 208C, the exit temperature of cold water is (a) 288C (b) 358C (c) 388C (d) 418C (e) 808C

An adiabatic heat exchanger is used to heat cold water at 158C entering at a rate of 5 kg/s by hot water at 908C entering at a rate of 4 kg/s. If the exit temperature of hot water is 508C, the exit temperature of cold water is (a) 428C (b) 478C (c) 558C (d) 788C (e) 908C

In a shower, cold water at 108C flowing at a rate of 5 kg/min is mixed with hot water at 608C flowing at a rate of 2 kg/min. The exit temperature of the mixture is (a) 24.38C (b) 35.08C (c) 40.08C (d) 44.38C (e) 55.28C

In a heating system, cold outdoor air at 78C flowing at a rate of 4 kg/min is mixed adiabatically with heated air at 708C flowing at a rate of 3 kg/min. The exit temperature of the mixture is (a) 348C (b) 398C (c) 458C (d) 638C (e) 778C

Hot combustion gases (assumed to have the properties of air at room temperature) enter a gas turbine at 1 MPa and 1500 K at a rate of 0.1 kg/s, and exit at 0.2 MPa and 900 K. If heat is lost from the turbine to the surroundings at a rate of 15 kJ/s, the power output of the gas turbine is (a) 15 kW (b) 30 kW (c) 45 kW (d) 60 kW (e) 75 kW

Steam expands in a turbine from 4 MPa and 5008C to 0.5 MPa and 2508C at a rate of 1350 kg/h. Heat is lost from the turbine at a rate of 25 kJ/s during the process. The power output of the turbine is (a) 157 kW (b) 207 kW (c) 182 kW (d) 287 kW (e) 246 kW

Steam is compressed by an adiabatic compressor from 0.2 MPa and 1508C to 0.8 MPa and 3508C at a rate of 1.30 kg/s. The power input to the compressor is (a) 511 kW (b) 393 kW (c) 302 kW (d) 717 kW (e) 901 kW

Refrigerant-134a is compressed by a compressor from the saturated vapor state at 0.14 MPa to 0.9 MPa and 608C at a rate of 0.108 kg/s. The refrigerant is cooled at a rate of 1.10 kJ/s during compression. The power input to the compressor is (a) 4.94 kW (b) 6.04 kW (c) 7.14 kW (d) 7.50 kW (e) 8.13 kW

Refrigerant-134a expands in an adiabatic turbine from 1.2 MPa and 1008C to 0.18 MPa and 508C at a rate of 1.25 kg/s. The power output of the turbine is (a) 44.7 kW (b) 66.4 kW (c) 72.7 kW (d) 89.2 kW (e) 112.0 kW

Refrigerant-134a at 1.4 MPa and 908C is throttled to a pressure of 0.6 MPa. The temperature of the refrigerant after throttling is (a) 228C (b) 568C (c) 828C (d) 808C (e) 908C

Air at 278C and 5 atm is throttled by a valve to 1 atm. If the valve is adiabatic and the change in kinetic energy is negligible, the exit temperature of air will be (a) 108C (b) 158C (c) 208C (d) 238C (e) 278C

Steam at 1 MPa and 3008C is throttled adiabatically to a pressure of 0.4 MPa. If the change in kinetic energy is negligible, the specific volume of the steam after throttling is (a) 0.358 m3 /kg (b) 0.233 m3 /kg (c) 0.375 m3 /kg (d) 0.646 m3 /kg (e) 0.655 m3 /kg

Air is to be heated steadily by an 8-kW electric resistance heater as it flows through an insulated duct. If the air enters at 508C at a rate of 2 kg/s, the exit temperature of air is (a) 46.08C (b) 50.08C (c) 54.08C (d) 55.48C (e) 58.08C

You have been given the responsibility of picking a steam turbine for an electrical-generation station that is to produce 300 MW of electrical power that will sell for $0.05 per kilowatt-hour. The boiler will produce steam at 700 psia and 7008F, and the condenser is planned to operate at 808F. The cost of generating and condensing the steam is $0.01 per kilowatt-hour of electricity produced. You have narrowed your selection to the three turbines in the table below. Your criterion for selection is to pay for the equipment as quickly as possible. Which turbine should you choose?

You are to design a small, directional control rocket to operate in space by providing as many as 100 bursts of 5 seconds each with a mass flow rate of 0.5 lbm/s at a velocity of 400 ft/s. Storage tanks that will contain up to 3000 psia are available, and the tanks will be located in an environment whose temperature is 408F. Your design criterion is to minimize the volume of the storage tank. Should you use a compressed-air or an R-134a system?

An air cannon uses compressed air to propel a projectile from rest to a final velocity. Consider an air cannon that is to accelerate a 10-gram projectile to a speed of 300 m/s using compressed air, whose temperature cannot exceed 208C. The volume of the storage tank is not to exceed 0.1 m3 . Select the storage volume size and maximum storage pressure that requires the minimum amount of energy to fill the tank.

Design a 1200-W electric hair dryer such that the air temperature and velocity in the dryer will not exceed 508C and 3 m/s, respectively.

Design a scalding unit for slaughtered chickens to loosen their feathers before they are routed to feather-picking machines with a capacity of 1200 chickens per hour under the following conditions: The unit will be of an immersion type filled with hot water at an average temperature of 538C at all times. Chicken with an average mass of 2.2 kg and an average temperature of 368C will be dipped into the tank, held in the water for 1.5 min, and taken out by a slow-moving conveyor. The chicken is expected to leave the tank 15 percent heavier as a result of the water that sticks to its surface. The center-to-center distance between chickens in any direction will be at least 30 cm. The tank can be as wide as 3 m and as high as 60 cm. The water is to be circulated through and heated by a natural gas furnace, but the temperature rise of water will not exceed 58C as it passes through the furnace. The water loss is to be made up by the city water at an average temperature of 168C. The walls and the floor of the tank are well-insulated. The unit operates 24 h a day and 6 days a week. Assuming reasonable values for the average properties, recommend reasonable values for (a) the mass flow rate of the makeup water that must be supplied to the tank, (b) the rate of heat transfer from the water to the chicken, in kW, (c) the size of the heating system in kJ/h, and (d) the operating cost of the scalding unit per month for a unit cost of $1.12/therm of natural gas.