You are asked to design a heating system for a swimming

Problem 161P An ideal gas undergoes a constant entropy (isen-tropic) process in a closed system. The heat transfer and work are, respectively (a)0,-cv?T ________________ (b) cv?T,0 ________________ (c) cp?T,RT ________________ (d) R In(T2/T1),R In(T2/T1)

Problem 1P An ideal gas at a given state expands to a fixed final volume first at constant pressure and then at constant temperature. For which case is the work done greater?

Problem 2P Nitrogen at an initial state of 300 K, 150 kPa, and 0.2 m3 is compressed slowly in an isothermal process to a final pressure of 800 kPa. Determine the work done during this process.

Problem 3P The volume of 1 kg of helium in a piston-cylinder device is initially 5 m3. Now helium is compressed to 2 m3 while its pressure is maintained constant at 180 kPa. Determine the initial and final temperatures of helium as well as the work required to compress it, in kJ.

Calculate the total work, in \(Btu\), for process 1–3 shown in Fig. P4–4E. FIGURE P4–4E Equation Transcription: Text Transcription: Btu

A piston-cylinder device with a set of stops initially contains \(0.6 \mathrm{~kg}\) of steam at \(1.0 \mathrm{MPa}\) and \(400^{\circ} \mathrm{C}\). The location of the stops corresponds to 40 percent of the initial volume. Now the steam is cooled. Determine the compression work if the final state is \((a) 1.0 \mathrm{MPa}\) and \(250^{\circ} \mathrm{C}\) and \((b) 500 \mathrm{kPa}\). (c) Also determine the temperature at the final state in part \((b)\). FIGURE P4–6 Equation Transcription: 400? 250? Text Transcription: 0.6 kg 1.0 MPa 400 degree celsius 250 degree celsius 500 kPa

Problem 5P A piston-cylinder device initially contains 0.07 m3 of nitrogen gas at 130 kPa and 120ºC. The nitrogen is now expanded polytropically to a state of 100 kPa and 100 C. Determine the boundary work done during this.process.

Problem 7P A piston-cylinder device initially contains 0.07 m3 of nitrogen gas at 130 kPa and 180°C. The nitrogen is now expanded to a pressure of 80 kPa polytropically with a polytropic exponent whose value is equal to the specific heat ratio (called isentropic expansion). Determine the final temperature and the boundary work done during this process.

Problem 8P A mass of 5kg of saturated water vapor at 300 kPa is heated at constant pressure until the temperature reaches 200°C. Calculate the work done by the steam during this process.

Problem 11P A mass of 1.5 kg of air at 120 kPa and 24°C is contained in a gas-tight, frictionless piston–cylinder device. The air is now compressed to a final pressure of 600 kPa. During the process, heat is transferred from the air such that the temperature inside the cylinder remains constant. Calculate the work input during this process.

Problem 9P 1-m3 of saturated liquid water at 200°C is expanded isothermally in a closed system until its quality is 80 percent. Determine the total work produced by this expansion, in kJ.

The equation of state of a gas is given as \(\bar{v}\left(P+10 / v^{-2}\right)=R_{u} T\), where the units of \(\bar{v}\) and \(P\) are \(m^{3} / \mathrm{km} \mathrm{ol}\) and \(k P a\), respectively. Now 0.2 \(\mathrm{~km} \mathrm{ol}\) of this gas is expanded in a quasi-equilibrium manner from 2 to \(4 m^{3}\) at a constant temperature of 350 K. Determine (a) the unit of the quantity 10 in the equation and (b) the work done during this isothermal expansion process. Equation Transcription: Text Transcription: bar v(P+10/v^-2)=R_uT v P m^3/km ol kPa 0.2km ol 4m^3

A frictionless piston-cylinder device contains \(5 \mathrm{~kg}\) of nitrogen at \(100 \mathrm{kPa}\) and \(250 \mathrm{~K}\). Nitrogen is now compressed slowly according to the relation \(P V^{1.4}=\) constant until it reaches a final temperature of \(360 \mathrm{~K}\). Calculate the work input during this process. FIGURE P4–14 Equation Transcription: Text Transcription: 5 kg 100 kPa 250 K PV^1.4= 360 K

Hydrogen is contained in a piston-cylinder device at \(14.7\) psia and \(15 \mathrm{ft}^{3}\). At this state, a linear spring \((F \propto x)\) with a spring constant of \(15,000 \mathrm{lbf} / \mathrm{ft}\) is touching the piston but exerts no force on it. The cross-sectional area of the piston is \(3 \mathrm{ft}^{2}\). Heat is transferred to the hydrogen, causing it to expand until its volume doubles. Determine (a) the final pressure, (b) the total work done by the hydrogen, and (c) the fraction of this work done against the spring. Also, show the process on a \(P-V\) diagram. Equation Transcription: () Text Transcription: 14.7 psia 15 ft^3 (F infinity x) 15,000 lbf/ft 3 ft^2 P-?

Problem 17P During an expansion process, the pressure of a gas changes from 15 to 100 psia according to the relation P = aV+ b,where a= 5 psia/ft3 and bis a constant. If the initial volume of the gas is 7 ft3, calculate the work done during the process.

Problem 20P A piston-cylinder device contains 0.15 kg of air initially at 2 MPa and 350°C. The air is first expanded isothermally to 500 kPa, then compressed polytropically with a polytropic exponent of 1.2 to the initial pressure, and finally compressed at the constant pressure to the initial state. Determine the boundary work for each process and toe net work of the cycle.

During some actual expansion and compression processes in piston-cylinder devices, the gases have been observed to satisfy the relationship \(P V^{n}=C\), where \(n\) and \(C\) are constants. Calculate the work done when a gas expands from \(350 \mathrm{kPa}\) and \(0.03 \mathrm{~m}^{3}\) to a final volume of \(0.2 \mathrm{~m}^{3}\) for the case of \(n=1.5\). Equation Transcription: Text Transcription: PV^n=C n C 350 kPa 0.03 m^3 0.2 m^3 n=1.5

4-18 A piston-cylinder device initially contains \(0.4 \mathrm{~kg}\) of nitrogen gas at \(160 \mathrm{kPa}\) and \(140^{\circ} \mathrm{C}\). The nitrogen is now expanded isothermally to a pressure of \(100 \mathrm{kPa}\). Determine the boundary work done during this process. Answer: \(23.0 \mathrm{~kJ}\) FIGURE P4–18 Equation Transcription: Text Transcription: 0.4 kg 160kPa 140 degrees celsius 100kPa

1-kg of water that is initially at \(90^{\circ} \mathrm{C}\) with a quality of 10 percent occupies a spring-loaded piston-cylinder device, such as that in Fig. P4-21. This device is now heated until the pressure rises to \(800 \mathrm{kPa}\) and the temperature is \(250^{\circ} \mathrm{C}\). Determine the total work produced during this process, in \(\mathrm{kJ}\). FIGURE P4–21 Equation Transcription: 90? 250? Text Transcription: 1-kg 90 degree celsius 800 kPa 250 degree celsius kJ

Problem 10P A gas is compressed from an initial volume of to a final volume of During the quasi-equilibrium process, the pressure changes with volume according to the relation Calculate the work done during this process (a) by plotting the process on a P-V diagram and finding the area under the process curve and (b) by performing the necessary integrations.

Problem 22P 0.75-kg water that is initially at 0.5 MPa and 30 percent quality occupies a spring-loaded piston–cylinder device. This device is now cooled until the water is a saturated liquid at 100°C. Calculate the total work produced during this process, in kJ.

Problem 27P A closed system undergoes a process in which there is no internal energy change. During this process, the system produces 1.1 X106 lbf·ft of work. Calculate the heat transfer for this process, in Btu.

A piston-cylinder device contains \(50 \mathrm{~kg}\) of water at \(250 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\). The cross-sectional area of the piston is \(0.1 \mathrm{~m}^{2}\). Heat is now transferred to the water, causing part of it to evaporate and expand. When the volume reaches \(0.2 \mathrm{~m}^{3}\), the piston reaches a linear spring whose spring constant is \(100 \mathrm{kN} / \mathrm{m}\). More heat is transferred to the water until the piston rises \(20 \mathrm{~cm}\) more. Determine (a) the final pressure and temperature and (b) the work done during this process. Also, show the process on a \(P-V\) diagram. FIGURE P4–24 Equation Transcription: 25? Text Transcription: 50 kg 250 kPa 25 degree celsius 0.1 m^2 0.2 m^3 20 cm P-V

Problem 28P A rigid container equipped with a stirring device contains 2.5 kg of motor oil. Determine the rate of specific energy increase when heat is transferred to the oil at a rate of 1 W, and 1.5 W of power is applied to the stirring device.

Problem 26P Complete the table below on the basis of the conservation of energy principle for a closed system. Qin Wout E1 E2 m e2-e1 Btu Btu Btu Btu Ibm Btu/lbm 350 — 1020 860 3 — 350 130 550 — 5 — — 260 600 — 2 150 ?500 — 1400 900 7 — — ?50 1000 — 3 ?200

Problem 30P A 20-ft3 rigid tank initially contains saturated refrigerant- 134a vapor at 160 psia. As a result of heat transfer from the refrigerant, the pressure drops to 50 psia. Show the process on a P-v diagram with respect to saturation lines, and determine (a) the final temperature, (b) the amount of refrigerant that has condensed, and (c) the heat transfer.

Problem 32P A fixed mass of saturated water vapor at 400 kPa is isothermally cooled until it is a saturated liquid. Calculate the amount of heat rejected during this process, in kJ/kg.

A \(0.5-\mathrm{m}^{3}\) rigid tank contains refrigerant- \(134 \mathrm{a}\) initially at \(160 \mathrm{kPa}\) and 40 percent quality. Heat is now transferred to the refrigerant until the pressure reaches \(700 \mathrm{kPa}\). Determine (a) the mass of the refrigerant in the tank and (b) the amount of heat transferred. Also, show the process on a \(P-V\) diagram with respect to saturation lines. Equation Transcription: Text Transcription: 0.5-m^3 134a 160 kPa 700 kPa P-v

Problem 33P A piston–cylinder device contains steam initially at 1 MPa, 450°C, and 2.5 m3 .Steam is allowed to cool at constant pressure until it first starts condensing. Show the process on a T-v diagram with respect to saturation lines and determine (a) the mass of the steam, (b) the final temperature, and (c) the amount of heat transfer.

A rigid 10- \(\mathrm{L}\) vessel initially contains a mixture of liquid water and vapor at \(100^{\circ} \mathrm{C}\) with \(12.3\) percent quality. The mixture is then heated until its temperature is \(150^{\circ} \mathrm{C}\). Calculate the heat transfer required for this process. Equation Transcription: 100°C 150°C Text Transcription: 10-L 100 degree celsius 150 degree celsius

An insulated piston-cylinder device contains \(5 \mathrm{~L}\) of saturated liquid water at a constant pressure of \(175 \mathrm{kPa}\). Water is stirred by a paddle wheel while a current of \(8 \mathrm{~A}\) flows for 45 min through a resistor placed in the water. If one-half of the liquid is evaporated during this constant-pressure process and the paddle-wheel work amounts to \9400 \mathrm{~kJ}\), determine the voltage of the source. Also, show the process on a \(P\) - \(v\) diagram with respect to saturation lines. Equation Transcription: Text Transcription: 5 L 175 kPa 45 min 400 kJ P-v

Reconsider Prob. 4-35. Using EES (or other) software, investigate the effect of the initial temperature of steam on the final temperature, the work done, and the total heat transfer. Let the initial temperature vary from 150 to \(250^{\circ} \mathrm{C}\). Plot the final results against the initial temperature, and discuss the results. Equation Transcription: 250°C Text Transcription: 250 degree celsius

A piston-cylinder device initially contains \(0.8 \mathrm{~m}^{3}\) of saturated water vapor at \(250 \mathrm{kPa}\). At this state, the piston is resting on a set of stops, and the mass of the piston is such that a pressure of \(300 \mathrm{kPa}\) is required to move it. Heat is now slowly transferred to the steam until the volume doubles. Show the process on a \(P-V\) diagram with respect to saturation lines and determine (a) the final temperature, (b) the work done during this process, and (c) the total heat transfer. Equation Transcription: P-v Text Transcription: 0.8 m^3 250 kPa 300 kPa P-v

Steam at \(75 \mathrm{kPa}\) and 8 percent quality is contained in a spring-loaded piston-cylinder device, as shown in Fig. P4-39, with an initial volume of \(2 \mathrm{~m}^{3}\). Steam is now heated until its volume is \(5 \mathrm{~m}^{3}\) and its pressure is \(225 \mathrm{kPa}\). Determine the heat transferred to and the work produced by the steam during this process. Equation Transcription: Text Transcription: 75 kPa 2 m^3 5 m^3 225 kPa

A piston-cylinder device initially contains steam at \(200 \mathrm{kPa}, 200^{\circ} \mathrm{C}\), and \(0.4 \mathrm{~m}^{3}\). At this state, a linear spring \((F \propto x)\) is touching the piston but exerts no force on it. Heat is now slowly transferred to the steam, causing the pressure and the volume to rise to \(250 \mathrm{kPa}\) and \(0.6 \mathrm{~m}^{3}\), respectively. Show the process on a \(P\)-\(v\) diagram with respect to saturation lines and determine (a) the final temperature, (b) the work done by the steam, and (c) the total heat transferred. Equation Transcription: °C Text Transcription: 200 kPa, 200 degree celsius 0.4 m^3 F propto x 250 kPa 0.6 m^3 P-v

An insulated tank is divided into two parts by a partition. One part of the tank contains \(2.5 \mathrm{~kg}\) of compressed liquid water at \(60^{\circ} \mathrm{C}\) and \(600 \mathrm{kPa}\) while the other part is evacuated. The partition is now removed, and the water expands to fill the entire tank. Determine the final temperature of the water and the volume of the tank for a final pressure of \(10 \mathrm{kPa}\). Equation Transcription: 60°C Text Transcription: 2.5 kg 60 degree celsius 600 kPa 10 kPa

Problem 45P Is the energy required to heat air from 295 to 305 K the same as the energy required to heat it from 345 to 355 K? Assume the pressure remains constant in both cases.

A \(40-\mathrm{L}\) electrical radiator containing heating oil is placed in a \(50-\mathrm{m}^{3}\) room. Both the room and the oil in the radiator are initially at \(10^{\circ} \mathrm{C}\). The radiator with a rating of \(2.4 \mathrm{~kW}\) is now turned on. At the same time, heat is lost from the room at an average rate of \(0.35 \mathrm{~kJ} / \mathrm{s}\). After some time, the average temperature is measured to be \(20^{\circ} \mathrm{C}\) for the air in the room, and \(50^{\circ} \mathrm{C}\) for the oil in the radiator. Taking the density and the specific heat of the oil to be \(950 \mathrm{~kg} / \mathrm{m}^{3}\) and \(2.2 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\), respectively, determine how long the heater is kept on. Assume the room is well-sealed so that there are no air leaks. Equation Transcription: 10°C 20°C 50°C °C Text Transcription: 40-L 50-m^3 10 degree calsius 2.4 kW 0.35 kJ/s 20 degree calsius 50 degree calsius 950 kg/m^3 2.2 kJ/kg degree calsius

Problem 40P Saturated R-134a vapor at 100°F is condensed at constant pressure to a saturated liquid in a closed piston-cylinder system. Calculate the heat transfer and work done during this process, in Btu/lbm.

Problem 43P Is the relation ?m = mc Vavg\ T restricted to constant-volume processes only, or can it be used for any kind of process of an ideal gas?

Problem 44P Is the relation ?h= mcv,avg?T restricted to constant-pressure processes only, or can it be used for any kind of process of an ideal gas?

Problem 46P A fixed mass of an ideal gas is heated from 50 to 80°C at a constant pressure of (a)1 atm and (b)3 atm. For which case do you think the energy required will be greater? Why?

Problem 47P A fixed mass of an ideal gas is heated from 50 to 80°C at a constant volume of (a)1 m3 and (b)3 m3. For which case do you think the energy required will be greater? Why?

Problem 48P A fixed mass of an ideal gas is heated from 50 to 80°C (a) at constant volume and (b) at constant pressure. For which case do you think the energy required will be greater? Why?

Show that for an ideal gas \(\bar{c}_{p}=\bar{c}_{v}+R_{u}\) Equation Transcription: Text Transcription: bar c_p=bar c_v+R_u

Problem 50P What is the change in the enthalpy, in kJ/kg, of oxygen as its temperature changes from 150 to 250°C? Is there any difference if the temperature change were from 0 to 100°C? Does the pressure at the beginning and end of this process have any effect on the enthalpy change?

Problem 51P Air is compressed from 20 psia and 70°F to 150 psia in a compressor. The compressor is operated such that the air temperature remains constant. Calculate the change in the specific volume of air as it passes through this compressor.

Problem 52P The temperature of 2 kg of neon is increased from 20 to 180°C. Calculate the change in the total internal energy of the neon, in kJ. Would the internal energy change be any different if the neon were replaced with argon?

Problem 53P Calculate the change in the enthalpy of argon, in kJ/kg, when it is cooled from 75 to 25°C. If neon had undergone this same change of temperature, would its enthalpy change have been any different?

Problem 54P Determine the internal energy change of hydrogen, in kJ/kg, as it is heated from 200 to 800 K, using (a) the empirical specific heat equation as a function of temperature (Table A–2c), (b) the cvalue at the average temperature (Table A–2b), and (c) the cvalue at room temperature (Table A–2a).

Determine the enthalpy change \(\Delta h\) of nitrogen, in \(\mathrm{kJ} / \mathrm{kg}\), as it is heated from 600 to \(1000 \mathrm{~K}\), using (a) the empirical specific heat equation as a function of temperature (Table A- 2 c ), (b) the \(c_{p}\) value at the average temperature (Table A- 2 b ), and (c) the \(c_{p}\) value at room temperature (Table A-2a). Equation Transcription: Text Transcription: Delta h kJ/kg 1000 K c_p

\(1-\mathrm{ft}^{3}\) of air is contained in the spring-loaded pistoncylinder device shown in Fig. P4-56E. The spring constant is \(5 \mathrm{lbf} / \mathrm{in}\), and the piston diameter is \(10 \mathrm{in}\). When no force is exerted by the spring on the piston, the state of the air is \(250 \mathrm{psia}\) and \(460^{\circ} \mathrm{F}\). This device is now cooled until the volume is one-half its original size. Determine the change in the specific internal energy and enthalpy of the air. Answers. Equation Transcription: 460°F Text Transcription: 1-ft^3 10 in 250 psia 460degree fahrenheit

Problem 57P Is it possible to compress an ideal gas isothermally in an adiabatic piston-cylinder device? Explain.

Problem 58P A 3-m3 rigid tank contains hydrogen at 250 kPa and 550 K. The gas is now cooled until its temperature drops to 350 K. Determine (a) the final pressure in the tank and (b) the amount of heat transfer.

Problem 61P Nitrogen gas to 20 psia and 100°F initially occupies a volume of 1 ft3 in a rigid container equipped with a stirring paddle wheel. After 5000 lbf ft of paddle wheel work is done on nitrogen, what is its final temperature?

Problem 60P A rigid tank contains 10 lbm of air at 30 psia and 65°F. The air is now heated until its pressure doubles. Determine (a) the volume of the tank and (b) the amount of heat transfer.

Problem 59P A 10-ft3 tank contains oxygen initially at 14.7 psia and 80°F. A paddle wheel within the tank is rotated until the pressure inside rises to 20 psia. During the process 20 Btu of heat is lost to the surroundings. Determine the paddlewheel work done. Neglect the energy stored in the paddle wheel.

4-62 An insulated rigid tank is divided into two equal parts by a partition. Initially, one part contains \(4 \mathrm{~kg}\) of an ideal gas at \(800 \mathrm{kPa}\) and \)50^{\circ} \mathrm{C}\), and the other part is evacuated. The partition is now removed, and the gas expands into the entire tank. Determine the final temperature and pressure in the tank. Equation Transcription: 50°C Text Transcription: 4 kg 800 kPa 50 degree celsius

Problem 63P A 4-m × 5-m × 6-m room is to be heated by a baseboard resistance heater. It is desired that the resistance heater be able to raise the air temperature in the room from 5 to 25°C within 11 min. Assuming no heat losses from the room and an atmospheric pressure of 100 kPa, determine the required power of the resistance heater. Assume constant specific heats at room temperature.

4-64 A student living in a 3-m \(\times 4-m \times 4\) - \(m\) dormitory room turns on her \(100-\mathrm{W}\) fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and windows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back \(8 \mathrm{~h}\) later. Use specific heat values at room temperature, and assume the room to be at \(100 \mathrm{kPa}\) and \(20^{\circ} \mathrm{C}\) in the morning when she leaves. Equation Transcription: 20°C Text Transcription: 3-m times 4-m times 4-m 100-W 100 kPa 20 degree celsius

A \94-\mathrm{m} \times 5-\mathrm{m} \times 7-\mathrm{m}\) room is heated by the radiator of a steam-heating system. The steam radiator transfers heat at a rate of \(10,000 \mathrm{~kJ} / \mathrm{h}\), and a \(100-\mathrm{W}\) fan is used to distribute the warm air in the room. The rate of heat loss from the room is estimated to be about \(5000 \mathrm{~kJ} / \mathrm{h}\). If the initial temperature of the room air is \(10^{\circ} \mathrm{C}\), determine how long it will take for the air temperature to rise to \(20^{\circ} \mathrm{C}\). Assume constant specific heats at room temperature. Equation Transcription: 10°C 20°C Text Transcription: 4-m times 5-m times 7-m 10,000 kJ/h 100-W 5000 kJ/h 10 degree celsius 20 degree celsius

Problem 67P An insulated piston–cylinder device contains 100 L of air at 400 kPa and 25°8C. A paddle wheel within the cylinder is rotated until 15 kJ of work is done on the air while the pressure is held constant. Determine the final temperature of the air. Neglect the energy stored in the paddle wheel.

A spring-loaded piston-cylinder device contains \(1 \mathrm{~kg}\) of carbon dioxide. This system is heated from \(100 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) to \(1000 \mathrm{kPa}\) and \(300^{\circ} \mathrm{C}\). Determine the total heat transfer to and work produced by this system. Equation Transcription: 25°C 300°C Text Transcription: 1 kg 100 kPa 25 degree celsius 300 degree celsius

Argon is compressed in a polytropic process with \(n= 1.2\) from \(120 \mathrm{kPa}\) and \(10^{\circ} \mathrm{C}\) to \(800 \mathrm{kPa}\) in a piston-cylinder device. Determine the work produced and heat transferred during this compression process, in \(\mathrm{kJ} / \mathrm{kg}\). Equation Transcription: 10°C Text Transcription: n = 1.2 120 kPa 10 degree celsius 800 kPa kJ/kg

Problem 69P A piston–cylinder device contains 25ft3 of nitrogen at 40 psia and 700°F. Nitrogen is now allowed to cool at constant pressure until the temperature drops to 200°F. Using specific heats at the average temperature, determine the amount of heat loss.

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. Initially, air is at \(400 \mathrm{kPa}\) and \(17^{\circ} \mathrm{C}\). The paddle wheel is now turned by an external electric motor until \(75 \mathrm{~kJ} / \mathrm{kg}\) of work has been transferred to air. During this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. Calculate the required amount of heat transfer, in \(\mathrm{kJ} / \mathrm{kg}\). Equation Transcription: 17°C Text Transcription: 400 kPa 17 degree celsius 75 kJ/kg kJ/kg

A mass of \(15 \mathrm{~kg}\) of air in a piston-cylinder device is heated from 25 to \(77^{\circ} \mathrm{C}\) by passing current through a resistance heater inside the cylinder. The pressure inside the cylinder is held constant at \(300 \mathrm{kPa}\) during the process, and a heat loss of \(60 \mathrm{~kJ}\) occurs. Determine the electric energy supplied, in kWh. Equation Transcription: 77°C Text Transcription: 15 kg 77 degree celsius 300 kPa 60 kJ kWh

A piston-cylinder device contains \(2.2 \mathrm{~kg}\) of nitrogen initially at \(100 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\). The nitrogen is now compressed slowly in a polytropic process during which \(P V^{1.3}=\) constant until the volume is reduced by one-half. Determine the work done and the heat transfer for this process. Equation Transcription: 25°C Text Transcription: 2.2 kg 100 kPa 25 degree celsius PV^1.3=

Problem 74P A piston–cylinder device contains 3 ft3 of air at 60 psia and 150°F. Heat is transferred to the air in the amount of 40 Btu as the air expands isothermally. Determine the amount of boundary work done during this process.

Problem 78P A piston–cylinder device contains 4 kg of argon at 250 kPa and 35°C. During a quasi-equilibrium, isothermal expansion process, 15 kJ of boundary work is done by the system, and 3 kJ of paddle-wheel work is done on the system. Determine the heat transfer for this process.

A piston-cylinder device, with a set of stops on the top, initially contains \(3 \mathrm{~kg}\) of air at \(200 \mathrm{kPa}\) and \(27^{\circ} \mathrm{C}\). Heat is now transferred to the air, and the piston rises until it hits the stops, at which point the volume is twice the initial volume. More heat is transferred until the pressure inside the cylinder also doubles. Determine the work done and the amount of heat transfer for this process. Also, show the process on a \(P-v\) diagram. Equation Transcription: 27°C Text Transcription: 3 kg 200 kPa 27degree celsius P-v

Problem 77P Air is contained in a piston-cylinder device at 600 kPa and 927°C, and occupies a volume of 0.8 m3. The air undergoes an isothermal (constant temperature) process until the pressure is reduced to 300 kPa. The piston is now fixed in place and not allowed to move while a heat transfer process takes place until the air reaches 27°C. (a) Sketch the system showing the energies crossing the boundary and the P-J diagram for the combined processes. ________________ (b) For the combined processes determine the net amount of heat transfer, in kJ, and its direction. Assume air has constant specific heats evaluated at 300 K.

Problem 79P The state of liquid water is changed from 50 psia and 50°F to 2000 psia and 100°F. Determine the change in the internal energy and enthalpy of water on the basis of the (a) compressed liquid tables, (b) incompressible substance approximation and property tables, and (c) specific-heat model.

Problem 80P During a picnic on a hot summer day, all the cold drinks disappeared quickly, and the only available drinks were those at the ambient temperature of 85°F. In an effort to cool a 12-fluid-oz drink in a can, a person grabs the can and starts shaking it in the iced water of the chest at 32°F. Using the properties of water for the drink, determine the mass of ice that will melt by the time the canned drink cools to 37°F.

Problem 82P Stainless steel ball bearings (? = 8085 kg/m3 and cp =0.480 kJ/kg-°C) having a diameter of 1.2 cm are to be quenched in water at a rate of 800 per minute. The balls leave the oven at a uniform temperature of 900°C and are exposed to air at 25°C for a while before they are dropped into the water. If the temperature of the balls drops to 850°C prior to quenching, determine the rate of heat transfer from the balls to the air.

Problem 85P An electronic device dissipating 25 W has a mass of 20 g and a specific heat of 850 J/kg-°C. The device is lightly used, and it is on for 5 min and then off for several hours, during which it cools to the ambient temperature of 25°C. Determine the highest possible temperature of the device at the end of the 5-min operating period. What would your answer be if the device were attached to a 0.5-kg aluminum heat sink? Assume the device and the heat sink to be nearly isothermal.

Consider a 1000-W iron whose base plate is made of \(0.5\)-cm-thick aluminum alloy 2024-T6 \(\left(\rho=2770 \mathrm{~kg} / \mathrm{m}^{3}\right.\) and \(c_{p}=875 \mathrm{~J} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\) ). The base plate has a surface area of \(0.03 \mathrm{~m}^{2}\). Initially, the iron is in thermal equilibrium with the ambient air at \(22^{\circ} \mathrm{C}\). Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach \(200^{\circ} \mathrm{C}\). Equation Transcription: °C 22°C 200°C Text Transcription: 0.5-cm rho= 2770 kg/m^3 c_p= 875 J/kg dot degree celsius 0.03 m^2 22 degree celsius 200°C

Problem 84P Long cylindrical steel rods (? = 7833 kg/m3 and cp =0.465 kJ/kg-°C),of 8-cm diameter are heat-treated,by drawing them at a velocity of 2 m/min through an oven maintained at 900°C if f]je rods enter the oven at 30°C and leave at a mean temperature of 700°C, determine the rate of heat transfer to the rods in the oven.

In a production facility, \(1.6\)-in-thick \(2-\mathrm{ft} \times 2-\mathrm{ft}\) square brass plates \9\left(\rho=532.5 \mathrm{lbm} / \mathrm{ft}^{3}\right.\) and \(\left.c_{p}=0.091 \mathrm{Btu} / \mathrm{lbm} \cdot{ }^{\circ} \mathrm{F}\right)\) that are initially at a uniform temperature of \975^{\circ} \mathrm{F}\) are heated by passing them through an oven at \(1500^{\circ} \mathrm{F}\) at a rate of 300 per minute. If the plates remain in the oven until their average temperature rises to \(900^{\circ} \mathrm{F}\), determine the rate of heat transfer to the plates in the furnace. Equation Transcription: -in Text Transcription: 1.6 -in 2-ft times 2-ft c_p=0.091Btu/lbm? F 75 degree Fahrenheit 1500 degree Fahrenheit 900 degree Fahrenheit

Reconsider Prob. 4–85. Using EES (or other) software, investigate the effect of the mass of the heat sink on the maximum device temperature. Let the mass of heat sink vary from 0 to \(1\ kg\). Plot the maximum temperature against the mass of heat sink, and discuss the results. Equation Transcription: Text Transcription: 1 kg

Problem 87P If you ever slapped someone or got slapped yourself, you probably remember the burning sensation. Imagine you had the unfortunate occasion of being slapped by an angry person, which caused the temperature of the affected area of your face to rise by 2.4°C (ouch!). Assuming the slapping hand has a mass of 0.9 kg and about 0.150 kg of the tissue on the face and the hand is affected by the incident, estimate the velocity of the hand just before impact. Take the specific heat of the tissue to be 3.8 kJ/kg·K.

Problem 90P Is the metabolizable energy content of a food the same as the energy released when it is burned in a bomb calorimeter? If not, how does it differ?

Problem 91P Is the number of prospective occupants an important consideration in the design of heating and cooling systems of classrooms? Explain.

In a manufacturing facility, \(5-\mathrm{cm}\)-diameter brass balls \(\left(\rho=8522 \mathrm{~kg} / \mathrm{m}^{3}\right.\) and \(\left.c_{p}=0.385 \mathrm{~kJ} / \mathrm{kg} \cdot{ }^{\circ} \mathrm{C}\right)\) initially at \(120^{\circ} \mathrm{C}\) are quenched in a water bath at \(50^{\circ} \mathrm{C}\) for a period of \(2 \mathrm{~min}\) at a rate of 100 balls per minute. If the temperature of the balls after quenching is \(74^{\circ} \mathrm{C}\), determine the rate at which heat needs to be removed from the water in order to keep its temperature constant at \(50^{\circ} \mathrm{C}\). Equation Transcription: Text Transcription: rho=8522 kg/m^3 c_p=0.385 kJ/kg dot degree celsius 120 degree celsius 50 degree celsius 2 min 74 degree celsius

Repeat Prob. 4–88 for aluminum balls.

Problem 92P What do you think of a diet program that allows for generous amounts of bread and rice provided that no butter or margarine is added?

Problem 93P The average specific heat of the human body is 3.6 kJ/kg°C. If the body temperature of an 80-kg man rises from 37°C to 39°C during strenuous exercise, determine the increase in the thermal energy of the body as a result of this rise in body temperature.

Problem 95P A 68-kg woman is planning to bicycle for an hour. If she is to meet her entire energy needs while bicycling by eating 30-g chocolate candy bars, determine how many candy bars she needs to take with her.

Problem 94P Consider two identical 80-kg men who are eating identical meals and doing identical things except that one of them jogs for 30 min every day while the other watches TV. Determine me weight difference between the two in a month.

Problem 96P A 90 - kg man gives in to temptation and eats an entire 1-L box of ice cream. How long does this man need to jog to burn off the calories he consumed from the ice cream?

Problem 97P A 60-kg man used to have an apple every day after dinner without losing or gaining any weight. He now eats a 200 - ml serving of ice cream instead of an apple and walks 20 min every day. On this new diet, how much weight will he lose or gain per month?

Problem 99P Consider two identical 50-kg women, Candy and Wendy, who are doing identical things and eating identical food except that Candy eats her baked potato with four teaspoons of butter while Wendy eats hers plain every evening. Determine the difference in the weights of Candy and Wendy after one year.

Problem 98P Consider a man who has 20 kg of body fat when he goes on a hunger strike. Determine how long he can survive on his body fat alone.

Problem 101P A 190-pound man and a 130-pound woman went to Burger King for lunch. The man had a BK Big Fish sandwich (720 Cal), medium french fries (400 Cal), and a large Coke (225 Cal). The woman had a basic hamburger (330 Cal), medium french fries (400 Cal), and a diet Coke (0 Cal). After lunch, they start shoveling snow and burn calories at a rate of 420 Cal/h for the woman and 610 Cal/h for the man. Determine how long each one of them needs to shovel snow to burn off the lunch calories.

Problem 102P A person eats a McDonald’s Big Mac sandwich (530 Cal), a second person eats a Burger King Whopper sandwich (640 Cal), and a third person eats 50 olives with regular french fries (350 Cal) for lunch. Determine who consumes the most calories. An olive contains about 5 Calories.

Problem 100P A woman who used to drink about one liter of regular cola every day switches to diet cola (zero calorie) and starts eating two slices of apple pie every day. Is she now consuming fewer or more calories?

Problem 103P A 75-kg man decides to lose 5 kg without cutting down his intake of 4000 Calories a day. Instead, he starts fast swimming, fast dancing, jogging, and biking each for an hour every day. He sleeps or relaxes the rest of the day. Determine how long it will take him to lose 5 kg.

Problem 104P The range of healthy weight for adults is usually expressed in terms of the body mass index(BMI), defined, in SI units, as where Wisthe weight (actually, the mass) ofthe person in kg and H is the height in m, and the range ofhealthy weight is 19 ? BMI ?= 25. Convert the previous formula to English units such that the weight is in pounds and the height in inches. Also, calculate your own BMI, and if it is not in the healthy range, determine how many pounds (or kg) you need to gain or lose to be fit.

Problem 105P The body mass index (BMI) of a 1.6-m tall woman who normally has 3 large slices of cheese pizza and a 400-ml Coke for lunch is 3,0. She now decides to change her lunch to 2 slices of pizza and a 200-ml Coke. Assuming that the deficit in the calorie intake is made up by burning body fat, determine how long it will take for the BMI of this person to drop to 20. Use the data in the text for calories and take the metabolizable energy content of 1 kg of body fat to be 33,100 kJ.

Problem 106P Alcohol provides 7 Calories per gram, but it provides no essential nutrients. A 1.5 ounce serving of 80-proof liquor contains 100 Calories in alcohol alone. Sweet wines and beer provide additional calories since they also contain carbohydrates. About 75 percent of American adults drink some sort of alcoholic beverage, which adds an average of 210 Calories a day to their diet. Determine how many pounds less an average American adult will weigh per year if he or she quit drinking alcoholic beverages and started drinking diet soda.

Problem 107P The temperature of air changes from 0 to 10°C while its velocity changes from zero to a final velocity, and its elevation changes from zero to a final elevation. At which values of final air velocity and final elevation will the internal, kinetic, and potential energy changes be equal?

Problem 110P Air is expanded in a polytropic process with n = 1.2 from 1 MPa and 400°C to 110 kPa in a piston-cylinder device. Determine the final temperature of the air.

Problem 108P Consider a piston–cylinder device that contains 0.5 kg air. Now, heat is transferred to the air at constant pressure and the air temperature increases by 5°C. Determine the expansion work done during this process.

Air in the amount of \(2 \mathrm{lbm}\) is contained in a well insulated, rigid vessel equipped with a stirring paddle wheel. The initial state of this air is 30 psia and \(60^{\circ} \mathrm{F}\). How much work, in Btu, must be transferred to the air with the paddle wheel to raise the air pressure to 40 psia? Also, what is the final temperature of air? Equation Transcription: 60°F Text Transcription: 2 lbm 30 psia 60 degree fahrenheit 40 psia

Problem 111P Nitrogen at 100 kPa and 25°C in a rigid vessel is heated until its pressure is 300 kPa. Calculate the work done and the heat transferred during this process, in kJ/kg.

Problem 112P A well-insulated rigid vessel contains 3 kg of saturated liquid water at 40°C. The vessel also contains an electrical resistor that draws 10 amperes when 50 volts are applied. Determine the final temperature in the vessel after the resistor has been operating for 30 minutes.

Problem 113P In order to cool 1 ton of water at 20°C in an insulated tank, a person pours 80 kg of ice at -5°C into the water. Determine the final equilibrium temperature in the tank. The melting temperature and the heat of fusion of ice at atmospheric pressure are 0°C and 333.7 kJ/kg, respectively.

A mags of \(3 \mathrm{~kg}\) of saturated liquid-vapor mixture of water is contained in a piston-cylinder device at \(160 \mathrm{kPa}\). Initially, \(1 \mathrm{~kg}\) of the water is in the liquid phase and the rest is in the vapor phase. Heat is now transferred to the water, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches \(500 \mathrm{kPa}\). Heat transfer continues until the total volume increases by 20 percent. Determine \((a)\) the initial and final temperatures, \((b)\) the mass of liquid water when the piston first starts moving, and \((c)\) the work done during this process. Also, show the process on a \(P-v\) diagram. Equation Transcription: Text Transcription: 3 kg 160 kPa 500 kPa P-v

Problem 116P Saturated water vapor at 200°C is condensed to a saturated liquid at 50°C in a spring-loaded piston-cylinder device. Determine the heat transfer for this process, in kJ/kg.

A mass of \(12 \mathrm{~kg}\) of saturated refrigerant-134a vapor is contained in a piston-cylinder device at \(240 \mathrm{kPa}\). Now \(300 \mathrm{~kJ}\) of heat is transferred to the refrigerant at constant pressure while a 110-V source supplies current to a resistor within the cylinder for \(6 \mathrm{~min}\). Determine the current supplied if the final temperature is \(70^{\circ} \mathrm{C}\). Also, show the process on a \(T-V\) di?gram with respect to the sáturation lines. Equation Transcription: 70°C Text Transcription: 12 kg 134a 240 kPa 300 kJ 110-V 70 degree celsius T-v

A piston-cylinder device contains helium gas initially at \(100 \mathrm{kPa}, 10^{\circ} \mathrm{C}\), and \(0.2 \mathrm{~m}^{3}\). The helium is now compressed in a polytropic process \(\left(P V^{n}=\right.\) constant) to \(700 \mathrm{kPa}\) and \(290^{\circ} \mathrm{C}\). Determine the heat loss or gain during this process. Equation Transcription: Text Transcription: 100 kPa,10 degree celsius 0.2 m^3 PV^n= 700kPa 290 degree celsius

A piston-cylinder device contains \(0.8 \mathrm{~kg}\) of an ideal gas. Now, the gas is cooled at constant pressure until its temperature decreases by \(10^{\circ} \mathrm{C}\). If \(16.6 \mathrm{~kJ}\) of compression work is done during this process, determine the gas constant and the molar mass of the gas. Also, determine the constant volume and constant-pressure specific heats of the gas if its specific heat ratio is \(1.667 .\) Equation Transcription: 10°C Text Transcription: 0.8 kg 10 degree celsius 16.6 kJ 1.667

An insulated piston-cylinder device initially contains \(0.01 \mathrm{~m}^{3}\) of saturated liquid-vapor mixture with a quality of \(0.2\) at \(120^{\circ} \mathrm{C}\). Now some ice at \(0^{\circ} \mathrm{C}\) is added to the cylinder. If the cylinder contains saturated liquid at \(120^{\circ} \mathrm{C}\) when thermal equilibrium is established, determine the amount of ice added. The melting temperature and the heat of fusion of ice at atmospheric pressure are \(0^{\circ} \mathrm{C}\) and \(333.7 \mathrm{~kJ} / \mathrm{kg}\), respectively. Equation Transcription: 120°C 0°C Text Transcription: 0.01 m^3 120 degree celsius 0 degree celsius 333.7 kJ/kg

Problem 120P Nitrogen gas is expanded in a polytropic process with n = 1.25 from 2 MPa and 1200 K to 200 kPa in a piston–cylinder device. How much work is produced and heat is transferred during this expansion process, in kJ/kg?

A passive solar house that is losing heat to the outdoors at an average rate of \(50,000 \mathrm{~kJ} / \mathrm{h}\) is maintained at \(22^{\circ} \mathrm{C}\) at all times during a winter night for \(10 \mathrm{~h}\). The house is to be heated by 50 glass containers each containing \(20 \mathrm{~L}\) of water that is heated to \(80^{\circ} \mathrm{C}\) during the day by absorbing solar energy. \(\mathrm{A}\) thermostat-controlled \(15-\mathrm{kW}\) back-up electric resistance heater turns on whenever necessary to keep the house at \(22^{\circ} \mathrm{C}\). (a) How long did the electric heating system run that night? (b) How long would the electric heater run that night if the house incorporated no solar heating? Equation Transcription: 22°C 80°C Text Transcription: 50,000 kJ/h 22 degree celsius 20 L 80 degree celsius

Problem 122P One ton (1000 kg) of liquid water at 50°C is brought into a well-insulated and well-sealed 4-m × 5-m × 6-m room initially at 15°C and 95 kPa. Assuming constant specific heats for both air and water at room temperature, determine the final equilibrium temperature in the room.

Problem 124P A 3-m x 4-m x 5-m room is to be heated by one ton the room. The room is losing heat to the outside at an average rate of 6000 kJ/h. The room is initially at 20°C and 100 kPa and is maintained at an average temperature of 20°C at all times. If the hot water is to meet the heating requirements of this room for a 24-h period, determine the minimum temperature of the water when it is first brought into the room. Assume constant specific heats for both air and water at room temperature.

Water is boiled at sea level in a coffee maker equipped with an immersion-type electric heating element. The coffee maker contains \(1 \mathrm{~L}\) of water when full. Once boiling starts, it is observed that half of the water in the coffee maker evaporates in \(25 \mathrm{~min}\). Determine the power rating of the electric heating element immersed in water. Also, determine how long it will take for this heater to raise the temperature of \(1 \mathrm{~L}\) of cold water from \(18^{\circ} \mathrm{C}\) to the boiling temperature. Equation Transcription: 18°C Text Transcription: 1 L 25 min 18 degree celsius

The energy content of a certain food is to be determined in a bomb calorimeter that contains \(3 \mathrm{~kg}\) of water by burning a \(2-\mathrm{g}\) sample of it in the presence of \(100 \mathrm{~g}\) of air in the reaction chamber. If the water temperature rises by \(3.2^{\circ} \mathrm{C}\) when equilibrium is established, determine the energy content of the food, in \(\mathrm{kJ} / \mathrm{kg}\), by neglecting the thermal energy stored in the reaction chamber and the energy supplied by the mixer. What is a rough estimate of the error involved in neglecting the thermal energy stored in the reaction chamber? Equation Transcription: 3.2°C Text Transcription: 3 kg 2-g 100 g 3.2 degree celsius kJ/kg

Problem 126P A 68-kg man whose average body temperature is 39°C drinks 1 L of cold water at 3°C in an effort to cool down. Taking the average specific heat of the human body to be 3.6 kJ/kg-°C, determine the drop in the average body temperature of this person under the influence of this cold water.

An insulated rigid tank initially contains 1.4-kg saturated liquid water at \(200^{\circ} \mathrm{C}\) and air. At this state, 25 percent of the volume is occupied by liquid water and the rest by air. Now an electric resistor placed in the tank is turned on, and the tank is observed to contain saturated water vapor after \(20 \mathrm{~min}\). Determine \((a)\) the volume of the tank, \((b)\) the final temperature, and \((c)\) the electric power rating of the resistor. Neglect energy added to the air. Equation Transcription: 200°C Text Transcription: 1.4-kg 200 degree celsius 20 min

Reconsider Prob. 4–128. Using EES (or other) software, investigate the effect of the initial temperature of the ice on the final mass required. Let the ice temperature vary from ?26 to \(0^{\circ} \mathrm{C}\). Plot the mass of ice against the initial temperature of ice, and discuss the results. Equation Transcription: 0°C Text Transcription: 0 degree celsius

Problem 128P A 0.3-L glass of water at 20°C is to be cooled with ice to 5°C. Determine how much ice needs to be added to the water, in grams, if the ice is at (a)0°C and (b)-20°C. Also determine how much water would be needed if the cooling is to be done with cold water at 0°C. The melting temperature and the heat of fusion of ice at atmospheric pressure are 0°C and 333.7 kJ/kg, respectively, and the density of water is 1 kg/L.

A well-insulated 3-m \(\times 4-m \times 6-m\) room initially at \(7^{\circ} \mathrm{C}\) is heated by the radiator of a steam heating system. The radiator has a volume of \(15 \mathrm{~L}\) and is filled with superheated vapor at \(200 \mathrm{kPa}\) and \(200^{\circ} \mathrm{C}\). At this moment both the inlet and the exit valves to the radiator are closed. A 120 -W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to \(100 \mathrm{kPa}\) after \(45 \mathrm{~min}\) as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine the average temperature of air in 45 min. Assume the air pressure in the room remains constant at \(100 \mathrm{kPa}\). Equation Transcription: 78°C 200°C Text Transcription: 3-m times 4-m times 6-m 78 degree celsius 15 L 200 kPa 200 degree celsius 120-W 100 kPa 45 min

Two rigid tanks are connected by a valve. Tank A contains \(0.2 \mathrm{~m}^{3}\) of water at \(400 \mathrm{kPa}\) and 80 percent quality. Tank B contains \(0.5 \mathrm{~m}^{3}\) of water at \(200 \mathrm{kPa}\) and \(250^{\circ} \mathrm{C}\). The valve is now opened, and the two tanks eventually come to the same state. Determine the pressure and the amount of heat transfer when the system reaches thermal equilibrium with the surroundings at \(25^{\circ} \mathrm{C}\). Equation Transcription: 250°C 258°C Text Transcription: 0.2 m^3 400 kPa 0.5 m^3 200 kPa 250 degree celsius 258 degree celsius

Problem 134P Repeat Prob. 4–144 by assuming the piston is made of 8 kg of copper initially at the average temperature of the two gases on both sides.

Consider a well-insulated horizontal rigid cylinder that is divided into two compartments by a piston that is free to move but does not allow either gas to leak into the other side. Initially, one side of the piston contains \(1 \mathrm{~m}^{3}\) of \(\mathrm{N}_{2}\) gas at \(500 \mathrm{kPa}\) and \(120^{\circ} \mathrm{C}\) while the other side contains \(1 \mathrm{~m}^{3}\) of He gas at \(500 \mathrm{kPa}\) and \(40^{\circ} \mathrm{C}\). Now thermal equilibrium is established in the cylinder as a result of heat transfer through the piston. Using constant specific heats at room temperature, determine the final equilibrium temperature in the cylinder. What would your answer be if the piston were not free to move? Equation Transcription: 120°C 40°C Text Transcription: 1 m^3 N_2 500 kPa 120 degree celsius 500 kPa 40 degree celsius

Reconsider Prob. 4–134. Using EES (or other) software, investigate the effect of the mass of the copper piston on the final equilibrium temperature. Let the mass of piston vary from 1 to \(10\ kg\). Plot the final tem-perature against the mass of piston, and discuss the results. Equation Transcription: Text Transcription: 10 kg

An insulated piston-cylinder device initially contains \(1.8-\mathrm{kg}\) saturated liquid water at \(120^{\circ} \mathrm{C}\). Now an electric resistor placed in the tank is turned on for \(10 \mathrm{~min}\) until the volume quadruples. Determine \((a)\) the volume of the tank, \((b)\) the final temperature, and \((c)\) the electrical power rating of the resistor. Equation Transcription: 120°C Text Transcription: 1.8-kg 120 degree celsius 10 min

Problem 137P A vertical 12-cm diameter piston-cylinder device contains an ideal gas at the ambient conditions of 1 bar and 24°C. Initially, the inner face of the piston is 20 cm from the base of the cylinder. Now an external shaft connected to the piston exerts a force corresponding to a boundary work*input of 0.1 kJ. The temperature of the gas remains constant during the process. Determine (a) the amount of heat transfer, (b) the final pressure in the cylinder, and (c) the distance that the piston is displaced.

Problem 138P A vertical 12-cm diameter piston–cylinder device contains an ideal gas at the ambient conditions of 1 bar and 24°C. Initially, the inner face of the piston is 20 cm from the base of the cylinder. Now an external shaft connected to the piston exerts a force corresponding to a boundary work input of 0.1 kJ. The temperature of the gas remains constant during the process. Determine (a) the amount of heat transfer, (b) the final pressure in the cylinder, and (c) the distance that the piston is displaced.

An insulated rigid tank is divided into two compartments of different volumes. Initially, each compartment contains the same ideal gas at identical pressure but at different temperatures and masses. The wall separating the two compartments is removed and the two gases are allowed to mix. Assuming constant specific heats, find the simplest expression for the mixture temperature written in the form \(T_{3}=f\left(\frac{m_{1}}{m_{3}}, \frac{m_{2}}{m_{3}}, T_{1}, T_{2}\right)\) where \(m_{3}\) and \(T_{3}\) are the mass and temperature of the final mixture, respectively. Equation Transcription: Text Transcription: T_3=f(m_1/m_3,m_2/m_3,T_1,T_2) m_3 T_3

A piston-cylinder device initially contains \(0.35-\mathrm{kg}\) steam at \(3.5 \mathrm{MPa}\), superheated by \(7.4^{\circ} \mathrm{C}\). Now the steam loses heat to the surroundings and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at \(200^{\circ} \mathrm{C}\). Determine (a) the final pressure and the quality (if mixture), (b) the boundary work, (c) the amount of heat transfer when the piston first hits the stops, (d) and the total heat transfer. Equation Transcription: 7.4°C 200°C Text Transcription: 0.35-kg 3.5 MPa 7.4 degree celsius 200 degree celsius

Problem 141P One kilogram of carbon dioxide is compressed from 0.5 MPa and 200°C to 3 MPa in a piston-cylinder device arranged to execute a polytropic process with n = 1.3. Use the compressibility factor to determine the final temperature.

Problem 142P In solar-heated buildings, energy is often stored as sensible heat in rocks, concrete, or water during the day for use at night. To minimize the storage space, it is desirable to use a material that can store a large amount of heat while experiencing a small temperature change. A large amount of heat can be stored essentially at constant temperature during a phase change process, and thus materials that change phase at about room temperature such as glaubers salt (sodium sulfate decahydrate), which has a melting point of 32°C and a heat of fusion of 329 kJ/L, are very suitable for this purpose. Determine how much heat can be stored in a 5-m3 storage space using (a) glaubers salt undergoing a phase change, (b) granite rocks with a heat capacity of 2.32 kJ/kg · °C and a temperature change of 20°C, and (c) water with a heat capacity of 4.00 kJ/k · °C and a temperature change of 20°C.

Problem 145P A 3-m3 rigid tank contains nitrogen gas at 500 kPa and 300 K. Now heat is transferred to the nitrogen in the tank and the pressure of nitrogen rises to 800 kPa. The work done during this process is (a) 500 kJ ________________ (b) 1500 ________________ (c) 0 kJ ________________ (d) 900 kJ ________________ (e) 2400kJ

The early steam engines were driven by the atmospheric pressure acting on the piston fitted into a cylinder filled with saturated steam. A vacuum was created in the cylinder by cooling the cylinder externally with cold water, and thus condensing the steam. Consider a piston-cylinder device with a piston surface area of \(0.1 \mathrm{~m}^{2}\) initially filled with \(0.05 \mathrm{~m}^{3}\) of saturated water vapor at the atmospheric pressure of \(100 \mathrm{kPa}\). Now cold water is poured outside the cylinder, and the steam inside starts condensing as a result of heat transfer to the cooling water outside. If the piston is stuck at its initial position, determine the friction force acting on the piston and the amount of heat transfer when the temperature inside the cylinder drops to \(30^{\circ} \mathrm{C}\). Equation Transcription: 30°C Text Transcription: 0.1 m^2 0.05 m^3 100 kPa 30 degree celsius

Problem 146P A 0.5-m3 rigid tank contains nitrogen gas at 600 kPa and 300 K. Now the gas is compressed isothermally to a volume of 0.1 m3. The work done on the gas during this compression process is (a) 720kJ ________________ (b) 483kJ ________________ (c) 240 kJ ________________ (d) 175 kJ ________________ (e) 143 kJ

Problem 144P The specific heat of a material is given in a strange unit to be c =3.60 kJ/kg °F. The specific heat of this material in the SI units of kf/kg-°C is (a) 2.00kJ/kg-°C ________________ (b) 3.20 kJ/kg-°C ________________ (c) 3.60 kJ/kg-°C ________________ (d) 4.80 kJ/kg-°C ________________ (e) 6.48 kJ/kg-°C

Problem 147P A well-sealed room contains 60 kg of air at 200 kPa and 25°C. Now solar energy enters the room at an average rate of 0.8 kJ/s while a 120-W fan is turned on to circulate the air in the room. If heat transfer through the walls is negligible, the air temperature in the room in 30 min will be (a) 25.6°C ________________ (b) 49.8°C ________________ (c) 53.4°C ________________ (d) 52.5°C ________________ (e) 63.4°C

Problem 148P A 2-kW baseboard electric resistance heater in a vacant room is turned on and kept on for 15 min. The mass of the air in the room is 75 kg, and the room is tightly sealed so that no air can leak in or out. The temperature rise of air at the end of 15 min is (a) 8.5°C ________________ (b) 12.4°C ________________ (c) 24.0°C ________________ (d) 33.4°C ________________ (e) 54.8°C

Problem 149P A room contains 75 kg of air at 100 kPa and 15°C. The room has a 250-W refrigerator (the refrigerator consumes 250 W of electricity when running), a 120-W TV, a 1.8-kW electric resistance heater, and a 50-W fan. During a cold winter day, it is observed that the refrigerator, the TV, the fan, and the electric resistance heater are running continuously but the air temperature in the room remains constant. The rate of heat loss from the room that day is (a) 5832 kJ/h ________________ (b) 6192 kJ/h ________________ (c) 7560 kJ/h ________________ (d) 7632 kJ/h ________________ (e) 7992 kJ/h

Problem 150P A piston-cylinder device contains 5 kg of air at 400 kPa and 30°C. During a quasi-equilibium isothermal expansion process, 15 kJ of boundary work is done by the system, and 3 kJ of paddle-wheel work is done on the system. The heat transfer during this process is (a) 12 kJ ________________ (b) 18 kf ________________ (c) 2.4kJ ________________ (d) 3.5kJ ________________ (e) 60 kJ

Problem 152P A glass of water with a mass of 0.45 kg at 20°C is to be cooled to 0°C by dropping ice cubes at 0°C into it. The latent heat of fusion of ice is 334 kJ/kg, and the specific heat of water is 4.18 kJ/kg·°C. The amount of ice that needs to be added is (a) 56g ________________ (b) 113 g ________________ (c) 124 g ________________ (d) 224 g ________________ (e) 450g

Problem 153P A 2-kW electric resistance heater submerged in 5-kg water is turned on and kept on for 10 min. During the process, 300 kJ of heat is lost from the water. The temperature rise of water is (a) 0.4°C ________________ (b) 43.1°C ________________ (c) 57.4°C ________________ (d) 71.8°C ________________ (e) 180°C

Problem 151P A 6-pack canned drink is to be cooled from 18°C to 3°C. The mass of each canned drink is 0.355 kg. The drinks can be treated as water, and the energy stored in the aluminum can itself is negligible. The amount of heat transfer from the 6 canned drinks is (a) 22kJ ________________ (b) 32kJ ________________ (c) 134 kJ ________________ (d) 187 kJ ________________ (e) 223 kJ

Problem 157P The specific heat at constant volume for an ideal gas is given by cv= 0.7 + (2.7 X 10_4) r (kJ/kg-K) where Tis in kelvin. The change in the internal energy for this ideal gas undergoing a process in which the temperature changes from 27 to 127°C is most nearly (a) 70kJ/kg ________________ (b) 72.1 kJ/kg ________________ (c)79.5 kJ/kg ________________ (d) 82.1 kJ/kg ________________ (e)84.0 kJ/kg

Problem 156P An apple with an average mass of 0.18 kg and average specific heat of 3.65 kJ/kg·°C is cooled from 22°C to 5°C. The amount of heat transferred from the apple is (a) 0.85 kJ ________________ (b)62.1 kJ ________________ (c) 17.7 kJ ________________ (d) l 1.2 kJ ________________ (e) 7.1 kJ

Problem 158P An ideal gas has a gas constant R =0.3 kJ/kg-K and a constant-volume specific heat cv =0.7 kJ/kg-K. If the gas has a temperature change of 100°C, choose the correct answer for each of the following: 1. The change in enthalpy is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine ________________ 2. The change in internal energy is, in kJ/kg (a) 30 (b)70 (c) 100 (d) insufficient information to determine ________________ 3. The work done is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine ________________ 4. The heat transfer is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine ________________ 5. The change in the pressure-volume product is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine

Problem 159P An ideal gas undergoes a constant temperature (isothermal) process in a closed system. The heat transfer and work are, respectively (a) 0,-cv?T ________________ (b) cv?T,0 ________________ (c) c p?T,RT ________________ (d) R In(T2/T1),R In(T2/T1)

Problem 154P 1.5 kg of liquid water initially at 12°C is to be heated at 95°C in a teapot equipped with a 800-W electric heating element inside. The specific heat of water can be taken to be 4.18 kJ/kg·°C, and the heat loss from the water during heating can be neglected. The time it takes to heat water to the desired temperature is (a)5.9 min ________________ (b)7.3 min ________________ (c) 10.8 min ________________ (d) 14.0 min ________________ (e) 17.0 min

Problem 155P An ordinary egg with a mass of 0.1 kg and a specific heat of 3.32 kJ/kg·°C is dropped into boiling water at 95°C. If the initial temperature of the egg is 5°C, the maximum amount of heat transfer to the egg is (a)121J ________________ (b)30kJ ________________ (c) 24 kJ ________________ (d) 18 kJ ________________ (e) infinity

Problem 160P An ideal gas undergoes a constant pressure (isobaric) process in a closed system. The heat transfer and work are, respectively (a)0,-cv?T ________________ (b) cv?T,0 ________________ (c) cp?T,RT ________________ (d) R In(T2/T1),R In(T2/T1)

Air is contained in a cylinder device fitted with a piston-cylinder. The piston initially rests on a set of stops, and a pressure of \(200 \mathrm{kPa}\) is required to move the piston. Initially, the air is at \(100 \mathrm{kPa}\) and \(23^{\circ} \mathrm{C}\) and occupies a volume of \(0.25 \mathrm{~m}^{3}\). Determine the amount of heat transferred to the air, in \(\mathrm{kJ}\), while increasing the temperature to \(700 \mathrm{~K}\). Assume air has constant specific heats evaluated at \(300 \mathrm{~K}\). Equation Transcription: Text Transcription: 200 kPa 100 kPa 23^circC 0.25 m^3 kJ 700 K 300 K

An ideal gas at a given state expands to a fixed final volume first at constant pressure and then at constant temperature. For which case is the work done greater?

Nitrogen at an initial state of 300 K, 150 kPa, and 0.2 m3 is compressed slowly in an isothermal process to a final pressure of 800 kPa. Determine the work done during this process.

Problem 4.43C Is the relation restricted to constant-volume processes only, or can it be used for any kind of process of an ideal gas?

Problem 4.44E Is the relation restricted to constant-pressure process only, or can it be used for any kind of process of an ideal gas?

Is the energy required to heat air from to the same as the energy required to heat it from to Assume the pressure remains constant in both cases.

A fixed mass of an ideal gas is heated from 50 to at a constant pressure of (a) 1 atm and (b) 3 atm. For which case do you think the energy required will be greater? Why?

A fixed mass of an ideal gas is heated from 50 to at a constant volume of (a) and (b) . For which case do you think the energy required will be greater? why?

A fixed mass of an ideal gas is heated from 50 to (a) at constant volume and (b) at constant pressure. For which case do you think the energy required will be greater?

Show that for an ideal gas

A gas is compressed from an initial volume of 0.42 m3 to a final volume of 0.12 m3 . During the quasi-equilibrium process, the pressure changes with volume according to the relation P 5 aV 1 b, where a 5 21200 kPa/m3 and b 5 600 kPa. Calculate the work done during this process (a) by plotting the process on a P-V diagram and finding the area under the process curve and (b) by performing the necessary integrations.

A mass of of air at and is contained in a gas-tight, frictionless piston-cylinder device. The air is now compressed to a final pressure of . During the process, heat is transferred from the air such that the temperature inside the cylinder remains constant. Calculate the work input during this process.

During some actual expansion and compression processes in pistoncylinder devices, the gases have been observed to satisfy the relationship PV n 5 C, where n and C are constants. Calculate the work done when a gas expands from 350 kPa and 0.03 m3 to a final volume of 0.2 m3 for the case of n 5 1.5.

Reconsider Prob. 412. Using the EES (or other) software, plot the process described in the problem on a P-V diagram, and investigate the effect of the polytropic exponent n on the boundary work. Let the polytropic exponent vary from 1.1 to 1.6. Plot the boundary work versus the polytropic exponent, and discuss the results.

A frictionless piston-cylinder device contains 5 kg of nitrogen at and . Nitrogen is now compressed slowly according to the relation until it reaches a final temperature of 360 K. Calculate the work input during this process.

The equation of state of a gas is given as v(P 1 10/ v2 ) 5 RuT, where the units of v and P are m3 /kmol and kPa, respectively. Now 0.2 kmol of this gas is expanded in a quasi-equilibrium manner from 2 to 4 m3 at a constant temperature of 350 K. Determine (a) the unit of the quantity 10 in the equation and (b) the work done during this isothermal expansion process.

Reconsider Prob. 415. Using the integration feature of the EES software, calculate the work done, and compare your result with the hand-calculated result obtained in Prob. 415. Plot the process described in the problem on a P-v diagram

During an expansion process, the pressure of a gas changes from according to the relation where and b is a constant. If the initial volume of the gas is , calculate the work done during the process.

A piston-cylinder device initially contains of nitrogen gas at and . The nitrogen is now expanded isothermally to a pressure of . Determine the boundary work done during this process.

Hydrogen is contained in a piston-cylinder device at and . At this state, a linear spring with a spring constant of is touching the piston but exerts no force on it. The cross-sectional area of the piston is . Heat is transferred to the hydrogen, causing it to expand until its volume doubles. Determine (a) the final pressure, (b) the total work done by the hydrogen, and (c) the fraction of this work done against the spring. Also, show the process on a diagram.

A piston-cylinder device contains of air initially at and . The air is first expanded isothermally to , then compressed polytropically with a polytropic exponent of 1.2 to the initial pressure, and finally compressed at the constant pressure to the initial state. Determine the boundary work for each process and the net work of the cycle.

1-kg of water that is initially at with a quality of 10 percent occupies a spring-loaded piston-cylinder device, such as that in. This device is now heated until the pressure rises to and the temperature is . Determine the total work produced during this process, in .

0.75-kg water that is initially at and 30 percent quality occupies a spring-loaded piston-cylinder device. This device is now cooled until the water is a saturated liquid at . Calculate the total work produced during this process, in .

An ideal gas undergoes two processes in a pistoncylinder device as follows: 1-2 Polytropic compression from T1 and P1 with a polytropic exponent n and a compression ratio of r 5 V1/V2. 2-3 Constant pressure expansion at P3 5 P2 until V35V1. (a) Sketch the processes on a single P-V diagram. (b) Obtain an expression for the ratio of the compressionto-expansion work as a function of n and r. (c) Find the value of this ratio for values of n 5 1.4 and r 5 6.

A pistoncylinder device contains 50 kg of water at 250 kPa and 258C. The cross-sectional area of the piston is 0.1 m2 . Heat is now transferred to the water, causing part of it to evaporate and expand. When the volume reaches 0.2 m3 , the piston reaches a linear spring whose spring constant is 100 kN/m. More heat is transferred to the water until the piston rises 20 cm more. Determine (a) the final pressure and temperature and (b) the work done during this process. Also, show the process on a P-V diagram.

Reconsider Prob. 424. Using the EES software, investigate the effect of the spring constant on the final pressure in the cylinder and the boundary work done. Let the spring constant vary from 50 kN/m to 500 kN/m. Plot the final pressure and the boundary work against the spring constant, and discuss the results.

Complete the table below on the basis of the conservation of energy principle for a closed system.

A closed system undergoes a process in which there is no internal energy change. During this process, the system produces 1.13106 1bfft of work. Calculate the heat transfer for this process, in Btu.

A rigid container equipped with a stirring device contains 2.5 kg of motor oil. Determine the rate of specific energy increase when heat is transferred to the oil at a rate of 1 W, and 1.5 W of power is applied to the stirring device.

A 0.5-m3 rigid tank contains refrigerant-134a initially at 160 kPa and 40 percent quality. Heat is now transferred to the refrigerant until the pressure reaches 700 kPa. Determine (a) the mass of the refrigerant in the tank and (b) the amount of heat transferred. Also, show the process on a P-v diagram with respect to saturation lines.

A 20-ft3 rigid tank initially contains saturated refrigerant-134a vapor at 160 psia. As a result of heat transfer from the refrigerant, the pressure drops to 50 psia. Show the process on a P-v diagram with respect to saturation lines, and determine (a) the final temperature, (b) the amount of refrigerant that has condensed, and (c) the heat transfer.

A rigid 10-L vessel initially contains a mixture of liquid water and vapor at 1008C with 12.3 percent quality. The mixture is then heated until its temperature is 1508C. Calculate the heat transfer required for this process.

A fixed mass of saturated water vapor at 400 kPa is isothermally cooled until it is a saturated liquid. Calculate the amount of heat rejected during this process, in kJ/kg.

A pistoncylinder device contains steam initially at 1 MPa, 4508C, and 2.5 m3 . Steam is allowed to cool at constant pressure until it first starts condensing. Show the process on a T-v diagram with respect to saturation lines and determine (a) the mass of the steam, (b) the final temperature, and (c) the amount of heat transfer.

An insulated pistoncylinder device contains 5 L of saturated liquid water at a constant pressure of 175 kPa. Water is stirred by a paddle wheel while a current of 8 A flows for 45 min through a resistor placed in the water. If one-half of the liquid is evaporated during this constant-pressure process and the paddle-wheel work amounts to 400 kJ, determine the voltage of the source. Also, show the process on a P-v diagram with respect to saturation lines.

A pistoncylinder device initially contains steam at 200 kPa, 2008C, and 0.4 m3 . At this state, a linear spring (F ~ x) is touching the piston but exerts no force on it. Heat is now slowly transferred to the steam, causing the pressure and the volume to rise to 250 kPa and 0.6 m3 , respectively. Show the process on a P-v diagram with respect to saturation lines and determine (a) the final temperature, (b) the work done by the steam, and (c) the total heat transferred.

Reconsider Prob. 435. Using EES (or other) software, investigate the effect of the initial temperature of steam on the final temperature, the work done, and the total heat transfer. Let the initial temperature vary from 150 to 2508C. Plot the final results against the initial temperature, and discuss the results.

A pistoncylinder device initially contains 0.8 m3 of saturated water vapor at 250 kPa. At this state, the piston is resting on a set of stops, and the mass of the piston is such that a pressure of 300 kPa is required to move it. Heat is now slowly transferred to the steam until the volume doubles. Show the process on a P-v diagram with respect to saturation lines and determine (a) the final temperature, (b) the work done during this process, and (c) the total heat transfer.

A 40-L electrical radiator containing heating oil is placed in a 50-m3 room. Both the room and the oil in the radiator are initially at 108C. The radiator with a rating of 2.4 kW is now turned on. At the same time, heat is lost from the room at an average rate of 0.35 kJ/s. After some time, the average temperature is measured to be 208C for the air in the room, and 508C for the oil in the radiator. Taking the density and the specific heat of the oil to be 950 kg/m3 and 2.2 kJ/kg8C, respectively, determine how long the heater is kept on. Assume the room is well-sealed so that there are no air leaks.

Steam at 75 kPa and 8 percent quality is contained in a spring-loaded pistoncylinder device, as shown in Fig. P439, with an initial volume of 2 m3 . Steam is now heated until its volume is 5 m3 and its pressure is 225 kPa. Determine the heat transferred to and the work produced by the steam during this process.

Saturated R-134a vapor at 1008F is condensed at constant pressure to a saturated liquid in a closed piston cylinder system. Calculate the heat transfer and work done during this process, in Btu/lbm.

An insulated tank is divided into two parts by a partition. One part of the tank contains 2.5 kg of compressed liquid water at 608C and 600 kPa while the other part is evacuated. The partition is now removed, and the water expands to fill the entire tank. Determine the final temperature of the water and the volume of the tank for a final pressure of 10 kPa.

Reconsider Prob. 441. Using EES (or other) software, investigate the effect of the initial pressure of water on the final temperature in the tank. Let the initial pressure vary from 100 to 600 kPa. Plot the final temperature against the initial pressure, and discuss the results

Is the relation Du 5 mcv,avgDT restricted to constantvolume processes only, or can it be used for any kind of process of an ideal gas?

Is the relation Dh 5 mcp,avg DT restricted to constant-pressure processes only, or can it be used for any kind of process of an ideal gas?

Is the energy required to heat air from 295 to 305 K the same as the energy required to heat it from 345 to 355 K? Assume the pressure remains constant in both cases.

A fixed mass of an ideal gas is heated from 50 to 808C at a constant pressure of (a) 1 atm and (b) 3 atm. For which case do you think the energy required will be greater? Why?

A fixed mass of an ideal gas is heated from 50 to 808C at a constant volume of (a) 1 m3 and (b) 3 m3 . For which case do you think the energy required will be greater? Why?

A fixed mass of an ideal gas is heated from 50 to 808C (a) at constant volume and (b) at constant pressure. For which case do you think the energy required will be greater? Why?

Show that for an ideal gas c _ p 5 c _ v1 Ru.

What is the change in the enthalpy, in kJ/kg, of oxygen as its temperature changes from 150 to 2508C? Is there any difference if the temperature change were from 0 to 1008C? Does the pressure at the beginning and end of this process have any effect on the enthalpy change?

Air is compressed from 20 psia and 708F to 150 psia in a compressor. The compressor is operated such that the air temperature remains constant. Calculate the change in the specific volume of air as it passes through this compressor.

The temperature of 2 kg of neon is increased from 20 to 1808C. Calculate the change in the total internal energy of the neon, in kJ. Would the internal energy change be any different if the neon were replaced with argon?

Calculate the change in the enthalpy of argon, in kJ/kg, when it is cooled from 75 to 258C. If neon had undergone this same change of temperature, would its enthalpy change have been any different?

Determine the internal energy change Du of hydrogen, in kJ/kg, as it is heated from 200 to 800 K, using (a) the empirical specific heat equation as a function of temperature (Table A2c), (b) the cv value at the average temperature (Table A2b), and (c) the cv value at room temperature (Table A2a).

Determine the enthalpy change Dh of nitrogen, in kJ/kg, as it is heated from 600 to 1000 K, using (a) the empirical specific heat equation as a function of temperature (Table A2c), (b) the cp value at the average temperature (Table A2b), and (c) the cp value at room temperature (Table A2a).

1-ft3 of air is contained in the spring-loaded pistoncylinder device shown in Fig. P456E. The spring constant is 5 lbf/in, and the piston diameter is 10 in. When no force is exerted by the spring on the piston, the state of the air is 250 psia and 4608F. This device is now cooled until the volume is one-half its original size. Determine the change in the specific internal energy and enthalpy of the air.

Is it possible to compress an ideal gas isothermally in an adiabatic pistoncylinder device? Explain.

A 3-m3 rigid tank contains hydrogen at 250 kPa and 550 K. The gas is now cooled until its temperature drops to 350 K. Determine (a) the final pressure in the tank and (b) the amount of heat transfer.

A 10-ft3 tank contains oxygen initially at 14.7 psia and 808F. A paddle wheel within the tank is rotated until the pressure inside rises to 20 psia. During the process 20 Btu of heat is lost to the surroundings. Determine the paddlewheel work done. Neglect the energy stored in the paddle wheel.

A rigid tank contains 10 lbm of air at 30 psia and 658F. The air is now heated until its pressure doubles. Determine (a) the volume of the tank and (b) the amount of heat transfer.

Nitrogen gas to 20 psia and 1008F initially occupies a volume of 1 ft3 in a rigid container equipped with a stirring paddle wheel. After 5000 lbfft of paddle wheel work is done on nitrogen, what is its final temperature?

An insulated rigid tank is divided into two equal parts by a partition. Initially, one part contains 4 kg of an ideal gas at 800 kPa and 508C, and the other part is evacuated. The partition is now removed, and the gas expands into the entire tank. Determine the final temperature and pressure in the tank.

A 4-m 3 5-m 3 6-m room is to be heated by a baseboard resistance heater. It is desired that the resistance heater be able to raise the air temperature in the room from 5 to 258C within 11 min. Assuming no heat losses from the room and an atmospheric pressure of 100 kPa, determine the required power of the resistance heater. Assume constant specific heats at room temperature.

A student living in a 3-m 3 4-m 3 4-m dormitory room turns on her 100-W fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and windows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back 8 h later. Use specific heat values at room temperature, and assume the room to be at 100 kPa and 208C in the morning when she leaves.

A 4-m 3 5-m 3 7-m room is heated by the radiator of a steam-heating system. The steam radiator transfers heat at a rate of 10,000 kJ/h, and a 100-W fan is used to distribute the warm air in the room. The rate of heat loss from the room is estimated to be about 5000 kJ/h. If the initial temperature of the room air is 108C, determine how long it will take for the air temperature to rise to 208C. Assume constant specific heats at room temperature.

Argon is compressed in a polytropic process with n 5 1.2 from 120 kPa and 108C to 800 kPa in a pistoncylinder device. Determine the work produced and heat transferred during this compression process, in kJ/kg.

An insulated pistoncylinder device contains 100 L of air at 400 kPa and 258C. A paddle wheel within the cylinder is rotated until 15 kJ of work is done on the air while the pressure is held constant. Determine the final temperature of the air. Neglect the energy stored in the paddle wheel.

A spring-loaded piston-cylinder device contains 1 kg of carbon dioxide. This system is heated from 100 kPa and 258C to 1000 kPa and 3008C. Determine the total heat transfer to and work produced by this system.

A pistoncylinder device contains 25 ft3 of nitrogen at 40 psia and 7008F. Nitrogen is now allowed to cool at constant pressure until the temperature drops to 2008F. Using specific heats at the average temperature, determine the amount of heat loss.

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. Initially, air is at 400 kPa and 178C. The paddle wheel is now turned by an external electric motor until 75 kJ/kg of work has been transferred to air. During this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. Calculate the required amount of heat transfer, in kJ/kg.

A mass of 15 kg of air in a pistoncylinder device is heated from 25 to 778C by passing current through a resistance heater inside the cylinder. The pressure inside the cylinder is held constant at 300 kPa during the process, and a heat loss of 60 kJ occurs. Determine the electric energy supplied, in kWh.

A pistoncylinder device contains 2.2 kg of nitrogen initially at 100 kPa and 258C. The nitrogen is now compressed slowly in a polytropic process during which PV 1.3 5 constant until the volume is reduced by one-half. Determine the work done and the heat transfer for this process.

Reconsider Prob. 472. Using EES (or other) software, plot the process described in the problem on a P-V diagram, and investigate the effect of the polytropic exponent n on the boundary work and heat transfer. Let the polytropic exponent vary from 1.0 to 1.4. Plot the boundary work and the heat transfer versus the polytropic exponent, and discuss the results.

A pistoncylinder device contains 3 ft3 of air at 60 psia and 1508F. Heat is transferred to the air in the amount of 40 Btu as the air expands isothermally. Determine the amount of boundary work done during this process.

A pistoncylinder device, with a set of stops on the top, initially contains 3 kg of air at 200 kPa and 278C. Heat is now transferred to the air, and the piston rises until it hits the stops, at which point the volume is twice the initial volume. More heat is transferred until the pressure inside the cylinder also doubles. Determine the work done and the amount of heat transfer for this process. Also, show the process on a P-v diagram.

Air is contained in a cylinder device fitted with a piston-cylinder. The piston initially rests on a set of stops, and a pressure of 200 kPa is required to move the piston. Initially, the air is at 100 kPa and 238C and occupies a volume of 0.25 m3 . Determine the amount of heat transferred to the air, in kJ, while increasing the temperature to 700 K. Assume air has constant specific heats evaluated at 300 K

Air is contained in a piston-cylinder device at 600 kPa and 9278C, and occupies a volume of 0.8 m3 . The air undergoes and isothermal (constant temperature) process until the pressure in reduced to 300 kPa. The piston is now fixed in place and not allowed to move while a heat transfer process takes place until the air reaches 278C. (a) Sketch the system showing the energies crossing the boundary and the P-V diagram for the combined processes. (b) For the combined processes determine the net amount of heat transfer, in kJ, and its direction. Assume air has constant specific heats evaluated at 300 K. 478 A pistoncylinder device contains 4 kg of argon at 250 kPa and 358C. During a quasi-equilibrium, isothermal expansion process, 15 kJ of boundary work is done by the system, and 3 kJ of paddle-wheel work is done on the system. Determine the heat transfer for this process.

The state of liquid water is changed from 50 psia and 508F to 2000 psia and 1008F. Determine the change in the internal energy and enthalpy of water on the basis of the (a) compressed liquid tables, (b) incompressible substance approximation and property tables, and (c) specific-heat model.

During a picnic on a hot summer day, all the cold drinks disappeared quickly, and the only available drinks were those at the ambient temperature of 858F. In an effort to cool a 12-fluid-oz drink in a can, a person grabs the can and starts shaking it in the iced water of the chest at 328F. Using the properties of water for the drink, determine the mass of ice that will melt by the time the canned drink cools to 378F.

Consider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (r 5 2770 kg/m3 and cp 5 875 J/kg8C). The base plate has a surface area of 0.03 m2 . Initially, the iron is in thermal equilibrium with the ambient air at 228C. Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 2008C.

Stainless steel ball bearings (r 5 8085 kg/m3 and cp 5 0.480 kJ/kg8C) having a diameter of 1.2 cm are to be quenched in water at a rate of 800 per minute. The balls leave the oven at a uniform temperature of 9008C and are exposed to air at 258C for a while before they are dropped into the water. If the temperature of the balls drops to 8508C prior to quenching, determine the rate of heat transfer from the balls to the air.

ln a production facility, 1.6-in-thick 2-ft 3 2-ft square brass plates (r 5 532.5 lbm/ft3 and cp 5 0.091 Btu/lbm8F) that are initially at a uniform temperature of 758F are heated by passing them through an oven at 15008F at a rate of 300 per minute. If the plates remain in the oven until their average temperature rises to 9008F, determine the rate of heat transfer to the plates in the furnace.

Long cylindrical steel rods (r 5 7833 kg/m3 and cp 5 0.465 kJ/kg8C) of 8-cm diameter are heat-treated by drawing them at a velocity of 2 m/min through an oven maintained at 9008C. If the rods enter the oven at 308C and leave at a mean temperature of 7008C, determine the rate of heat transfer to the rods in the oven.

An electronic device dissipating 25 W has a mass of 20 g and a specific heat of 850 J/kg8C. The device is lightly used, and it is on for 5 min and then off for several hours, during which it cools to the ambient temperature of 258C. Determine the highest possible temperature of the device at the end of the 5-min operating period. What would your answer be if the device were attached to a 0.5-kg aluminum heat sink? Assume the device and the heat sink to be nearly isothermal.

Reconsider Prob. 485. Using EES (or other) software, investigate the effect of the mass of the heat sink on the maximum device temperature. Let the mass of heat sink vary from 0 to 1 kg. Plot the maximum temperature against the mass of heat sink, and discuss the results.

If you ever slapped someone or got slapped yourself, you probably remember the burning sensation. Imagine you had the unfortunate occasion of being slapped by an angry person, which caused the temperature of the affected area of your face to rise by 2.48C (ouch!). Assuming the slapping hand has a mass of 0.9 kg and about 0.150 kg of the tissue on the face and the hand is affected by the incident, estimate the velocity of the hand just before impact. Take the specific heat of the tissue to be 3.8 kJ/kgK.

In a manufacturing facility, 5-cm-diameter brass balls (r 5 8522 kg/m3 and cp 5 0.385 kJ/kg 8C) initially at 1208C are quenched in a water bath at 508C for a period of 2 min at a rate of 100 balls per minute. If the temperature of the balls after quenching is 748C, determine the rate at which heat needs to be removed from the water in order to keep its temperature constant at 508C.

Repeat Prob. 488 for aluminum balls.

Is the metabolizable energy content of a food the same as the energy released when it is burned in a bomb calorimeter? If not, how does it differ?

Is the number of prospective occupants an important consideration in the design of heating and cooling systems of classrooms? Explain.

What do you think of a diet program that allows for generous amounts of bread and rice provided that no butter or margarine is added?

The average specific heat of the human body is 3.6 kJ/kg 8C. If the body temperature of an 80-kg man rises from 378C to 398C during strenuous exercise, determine the increase in the thermal energy of the body as a result of this rise in body temperature.

Consider two identical 80-kg men who are eating identical meals and doing identical things except that one of them jogs for 30 min every day while the other watches TV. Determine the weight difference between the two in a month.

A 68-kg woman is planning to bicycle for an hour. If she is to meet her entire energy needs while bicycling by eating 30-g chocolate candy bars, determine how many candy bars she needs to take with her.

A 90-kg man gives in to temptation and eats an entire 1-L box of ice cream. How long does this man need to jog to burn off the calories he consumed from the ice cream?

A 60-kg man used to have an apple every day after dinner without losing or gaining any weight. He now eats a 200-ml serving of ice cream instead of an apple and walks 20 min every day. On this new diet, how much weight will he lose or gain per month?

Consider a man who has 20 kg of body fat when he goes on a hunger strike. Determine how long he can survive on his body fat alone.

Consider two identical 50-kg women, Candy and Wendy, who are doing identical things and eating identical food except that Candy eats her baked potato with four teaspoons of butter while Wendy eats hers plain every evening. Determine the difference in the weights of Candy and Wendy after one year.

A woman who used to drink about one liter of regular cola every day switches to diet cola (zero calorie) and starts eating two slices of apple pie every day. Is she now consuming fewer or more calories?

A 190-pound man and a 130-pound woman went to Burger King for lunch. The man had a BK Big Fish sandwich (720 Cal), medium french fries (400 Cal), and a large Coke (225 Cal). The woman had a basic hamburger (330 Cal), medium french fries (400 Cal), and a diet Coke (0 Cal). After lunch, they start shoveling snow and burn calories at a rate of 420 Cal/h for the woman and 610 Cal/h for the man. Determine how long each one of them needs to shovel snow to burn off the lunch calories

A person eats a McDonalds Big Mac sandwich (530 Cal), a second person eats a Burger King Whopper sandwich (640 Cal), and a third person eats 50 olives with regular french fries (350 Cal) for lunch. Determine who consumes the most calories. An olive contains about 5 Calories.

A 75-kg man decides to lose 5 kg without cutting down his intake of 4000 Calories a day. Instead, he starts fast swimming, fast dancing, jogging, and biking each for an hour every day. He sleeps or relaxes the rest of the day. Determine how long it will take him to lose 5 kg.

The range of healthy weight for adults is usually expressed in terms of the body mass index (BMI), defined, in SI units, as BMI 5 W (kg) H2 (m2 ) where W is the weight (actually, the mass) of the person in kg and H is the height in m, and the range of healthy weight is 19 # BMI $ 25. Convert the previous formula to English units such that the weight is in pounds and the height in inches. Also, calculate your own BMI, and if it is not in the healthy range, determine how many pounds (or kg) you need to gain or lose to be fit.

The body mass index (BMI) of a 1.6-m tall woman who normally has 3 large slices of cheese pizza and a 400-ml Coke for lunch is 30. She now decides to change her lunch to 2 slices of pizza and a 200-ml Coke. Assuming that the deficit in the calorie intake is made up by burning body fat, determine how long it will take for the BMI of this person to drop to 20. Use the data in the text for calories and take the metabolizable energy content of 1 kg of body fat to be 33,100 kJ.

Alcohol provides 7 Calories per gram, but it provides no essential nutrients. A 1.5 ounce serving of 80-proof liquor contains 100 Calories in alcohol alone. Sweet wines and beer provide additional calories since they also contain carbohydrates. About 75 percent of American adults drink some sort of alcoholic beverage, which adds an average of 210 Calories a day to their diet. Determine how many pounds less an average American adult will weigh per year if he or she quit drinking alcoholic beverages and started drinking diet soda.

The temperature of air changes from 0 to 108C while its velocity changes from zero to a final velocity, and its elevation changes from zero to a final elevation. At which values of final air velocity and final elevation will the internal, kinetic, and potential energy changes be equal?

Consider a pistoncylinder device that contains 0.5 kg air. Now, heat is transferred to the air at constant pressure and the air temperature increases by 58C. Determine the expansion work done during this process.

Air in the amount of 2 lbm is contained in a wellinsulated, rigid vessel equipped with a stirring paddle wheel. The initial state of this air is 30 psia and 608F. How much work, in Btu, must be transferred to the air with the paddle wheel to raise the air pressure to 40 psia? Also, what is the final temperature of air?

Air is expanded in a polytropic process with n 5 1.2 from 1 MPa and 4008C to 110 kPa in a piston-cylinder device. Determine the final temperature of the air.

Nitrogen at 100 kPa and 258C in a rigid vessel is heated until its pressure is 300 kPa. Calculate the work done and the heat transferred during this process, in kJ/kg.

A well-insulated rigid vessel contains 3 kg of saturated liquid water at 408C. The vessel also contains an electrical resistor that draws 10 amperes when 50 volts are applied. Determine the final temperature in the vessel after the resistor has been operating for 30 minutes.

In order to cool 1 ton of water at 208C in an insulated tank, a person pours 80 kg of ice at 258C into the water. Determine the final equilibrium temperature in the tank. The melting temperature and the heat of fusion of ice at atmospheric pressure are 08C and 333.7 kJ/kg, respectively.

A mass of 3 kg of saturated liquidvapor mixture of water is contained in a pistoncylinder device at 160 kPa. Initially, 1 kg of the water is in the liquid phase and the rest is in the vapor phase. Heat is now transferred to the water, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 500 kPa. Heat transfer continues until the total volume increases by 20 percent. Determine (a) the initial and final temperatures, (b) the mass of liquid water when the piston first starts moving, and (c) the work done during this process. Also, show the process on a P-v diagram.

A mass of 12 kg of saturated refrigerant-134a vapor is contained in a pistoncylinder device at 240 kPa. Now 300 kJ of heat is transferred to the refrigerant at constant pressure while a 110-V source supplies current to a resistor within the cylinder for 6 min. Determine the current supplied if the final temperature is 708C. Also, show the process on a T-v diagram with respect to the saturation lines.

Saturated water vapor at 2008C is condensed to a saturated liquid at 508C in a spring-loaded piston-cylinder device. Determine the heat transfer for this process, in kJ/kg.

A pistoncylinder device contains 0.8 kg of an ideal gas. Now, the gas is cooled at constant pressure until its temperature decreases by 108C. If 16.6 kJ of compression work is done during this process, determine the gas constant and the molar mass of the gas. Also, determine the constantvolume and constant-pressure specific heats of the gas if its specific heat ratio is 1.667.

A pistoncylinder device contains helium gas initially at 100 kPa, 108C, and 0.2 m3 . The helium is now compressed in a polytropic process (PV n 5 constant) to 700 kPa and 2908C. Determine the heat loss or gain during this process.

An insulated pistoncylinder device initially contains 0.01 m3 of saturated liquidvapor mixture with a quality of 0.2 at 1208C. Now some ice at 08C is added to the cylinder. If the cylinder contains saturated liquid at 1208C when thermal equilibrium is established, determine the amount of ice added. The melting temperature and the heat of fusion of ice at atmospheric pressure are 08C and 333.7 kJ/kg, respectively.

Nitrogen gas is expanded in a polytropic process with n 5 1.25 from 2 MPa and 1200 K to 200 kPa in a pistoncylinder device. How much work is produced and heat is transferred during this expansion process, in kJ/kg?

A passive solar house that is losing heat to the outdoors at an average rate of 50,000 kJ/h is maintained at 228C at all times during a winter night for 10 h. The house is to be heated by 50 glass containers each containing 20 L of water that is heated to 808C during the day by absorbing solar energy. A thermostat-controlled 15-kW back-up electric resistance heater turns on whenever necessary to keep the house at 228C. (a) How long did the electric heating system run that night? (b) How long would the electric heater run that night if the house incorporated no solar heating?

One ton (1000 kg) of liquid water at 508C is brought into a well-insulated and well-sealed 4-m 3 5-m 3 6-m room initially at 158C and 95 kPa. Assuming constant specific heats for both air and water at room temperature, determine the final equilibrium temperature in the room.

Water is boiled at sea level in a coffee maker equipped with an immersion-type electric heating element. The coffee maker contains 1 L of water when full. Once boiling starts, it is observed that half of the water in the coffee maker evaporates in 25 min. Determine the power rating of the electric heating element immersed in water. Also, determine how long it will take for this heater to raise the temperature of 1 L of cold water from 188C to the boiling temperature

A 3-m 3 4-m 3 5-m room is to be heated by one ton (1000 kg) of liquid water contained in a tank that is placed in the room. The room is losing heat to the outside at an average rate of 6000 kJ/h. The room is initially at 208C and 100 kPa and is maintained at an average temperature of 208C at all times. If the hot water is to meet the heating requirements of this room for a 24-h period, determine the minimum temperature of the water when it is first brought into the room. Assume constant specific heats for both air and water at room temperature.

The energy content of a certain food is to be determined in a bomb calorimeter that contains 3 kg of water by burning a 2-g sample of it in the presence of 100 g of air in the reaction chamber. If the water temperature rises by 3.28C when equilibrium is established, determine the energy content of the food, in kJ/kg, by neglecting the thermal energy stored in the reaction chamber and the energy supplied by the mixer. What is a rough estimate of the error involved in neglecting the thermal energy stored in the reaction chamber?

A 68-kg man whose average body temperature is 398C drinks 1 L of cold water at 38C in an effort to cool down. Taking the average specific heat of the human body to be 3.6 kJ/kg8C, determine the drop in the average body temperature of this person under the influence of this cold water.

An insulated rigid tank initially contains 1.4-kg saturated liquid water at 2008C and air. At this state, 25 percent of the volume is occupied by liquid water and the rest by air. Now an electric resistor placed in the tank is turned on, and the tank is observed to contain saturated water vapor after 20 min. Determine (a) the volume of the tank, (b) the final temperature, and (c) the electric power rating of the resistor. Neglect energy added to the air.

A 0.3-L glass of water at 208C is to be cooled with ice to 58C. Determine how much ice needs to be added to the water, in grams, if the ice is at (a) 08C and (b) 2208C. Also determine how much water would be needed if the cooling is to be done with cold water at 08C. The melting temperature and the heat of fusion of ice at atmospheric pressure are 08C and 333.7 kJ/kg, respectively, and the density of water is 1 kg/L.

Reconsider Prob. 4128. Using EES (or other) software, investigate the effect of the initial temperature of the ice on the final mass required. Let the ice temperature vary from 226 to 08C. Plot the mass of ice against the initial temperature of ice, and discuss the results.

A well-insulated 3-m 3 4-m 3 6-m room initially at 78C is heated by the radiator of a steam heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 2008C. At this moment both the inlet and the exit valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 45 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine the average temperature of air in 45 min. Assume the air pressure in the room remains constant at 100 kPa.

Two rigid tanks are connected by a valve. Tank A contains 0.2 m3 of water at 400 kPa and 80 percent quality. Tank B contains 0.5 m3 of water at 200 kPa and 2508C. The valve is now opened, and the two tanks eventually come to the same state. Determine the pressure and the amount of heat transfer when the system reaches thermal equilibrium with the surroundings at 258C.

Reconsider Prob. 4131. Using EES (or other) software, investigate the effect of the environment temperature on the final pressure and the heat transfer. Let the environment temperature vary from 0 to 508C. Plot the final results against the environment temperature, and discuss the results.

Consider a well-insulated horizontal rigid cylinder that is divided into two compartments by a piston that is free to move but does not allow either gas to leak into the other side. Initially, one side of the piston contains 1 m3 of N2 gas at 500 kPa and 1208C while the other side contains 1 m3 of He gas at 500 kPa and 408C. Now thermal equilibrium is established in the cylinder as a result of heat transfer through the piston. Using constant specific heats at room temperature, determine the final equilibrium temperature in the cylinder. What would your answer be if the piston were not free to move?

Repeat Prob. 4133 by assuming the piston is made of 8 kg of copper initially at the average temperature of the two gases on both sides.

Reconsider Prob. 4134. Using EES (or other) software, investigate the effect of the mass of the copper piston on the final equilibrium temperature. Let the mass of piston vary from 1 to 10 kg. Plot the final temperature against the mass of piston, and discuss the results.

An insulated piston-cylinder device initially contains 1.8-kg saturated liquid water at 1208C. Now an electric resistor placed in the tank is turned on for 10 min until the volume quadruples. Determine (a) the volume of the tank, (b) the final temperature, and (c) the electrical power rating of the resistor.

A vertical 12-cm diameter pistoncylinder device contains an ideal gas at the ambient conditons of 1 bar and 248C. Initially, the inner face of the piston is 20 cm from the base of the cylinder. Now an external shaft connected to the piston exerts a force corresponding to a boundary work input of 0.1 kJ. The temperature of the gas remains constant during the process. Determine (a) the amount of heat transfer, (b) the final pressure in the cylinder, and (c) the distance that the piston is displaced.

A vertical 12-cm diameter pistoncylinder device contains an ideal gas at the ambient conditons of 1 bar and 248C. Initially, the inner face of the piston is 20 cm from the base of the cylinder. Now an external shaft connected to the piston exerts a force corresponding to a boundary work input of 0.1 kJ. The temperature of the gas remains constant during the process. Determine (a) the amount of heat transfer, (b) the final pressure in the cylinder, and (c) the distance that the piston is displaced.

A pistoncylinder device initially contains 0.35-kg steam at 3.5 MPa, superheated by 7.48C. Now the steam loses heat to the surroundings and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 2008C. Determine (a) the final pressure and the quality (if mixture), (b) the boundary work, (c) the amount of heat transfer when the piston first hits the stops, (d) and the total heat transfer

An insulated rigid tank is divided into two compartments of different volumes. Initially, each compartment contains the same ideal gas at identical pressure but at different temperatures and masses. The wall separating the two compartments is removed and the two gases are allowed to mix. Assuming constant specific heats, find the simplest expression for the mixture temperature written in the form T3 5 f a m1 m3 , m2 m3 , T1, T2b where m3 and T3 are the mass and temperature of the final mixture, respectively.

One kilogram of carbon dioxide is compressed from 0.5 MPa and 2008C to 3 MPa in a piston-cylinder device arranged to execute a polytropic process with n 5 1.3. Use the compressibility factor to determine the final temperature.

In solar-heated buildings, energy is often stored as sensible heat in rocks, concrete, or water during the day for use at night. To minimize the storage space, it is desirable to use a material that can store a large amount of heat while experiencing a small temperature change. A large amount of heat can be stored essentially at constant temperature during a phase change process, and thus materials that change phase at about room temperature such as glaubers salt (sodium sulfate decahydrate), which has a melting point of 328C and a heat of fusion of 329 kJ/L, are very suitable for this purpose. Determine how much heat can be stored in a 5-m3 storage space using (a) glaubers salt undergoing a phase change, (b) granite rocks with a heat capacity of 2.32 kJ/kg 8C and a temperature change of 208C, and (c) water with a heat capacity of 4.00 kJ/k 8C and a temperature change of 208C.

The early steam engines were driven by the atmospheric pressure acting on the piston fitted into a cylinder filled with saturated steam. A vacuum was created in the cylinder by cooling the cylinder externally with cold water, and thus condensing the steam. Consider a pistoncylinder device with a piston surface area of 0.1 m2 initially filled with 0.05 m3 of saturated water vapor at the atmospheric pressure of 100 kPa. Now cold water is poured outside the cylinder, and the steam inside starts condensing as a result of heat transfer to the cooling water outside. If the piston is stuck at its initial position, determine the friction force acting on the piston and the amount of heat transfer when the temperature inside the cylinder drops to 308C.

The specific heat of a material is given in a strange unit to be c 5 3.60 kJ/kg8F. The specific heat of this material in the SI units of kJ/kg8C is (a) 2.00 kJ/kg8C (b) 3.20 kJ/kg8C (c) 3.60 kJ/kg8C (d) 4.80 kJ/kg8C (e) 6.48 kJ/kg8C

A 3-m3 rigid tank contains nitrogen gas at 500 kPa and 300 K. Now heat is transferred to the nitrogen in the tank and the pressure of nitrogen rises to 800 kPa. The work done during this process is (a) 500 kJ (b) 1500 kJ (c) 0 kJ (d) 900 kJ (e) 2400 kJ

A 0.5-m3 rigid tank contains nitrogen gas at 600 kPa and 300 K. Now the gas is compressed isothermally to a volume of 0.1 m3 . The work done on the gas during this compression process is (a) 720 kJ (b) 483 kJ (c) 240 kJ (d) 175 kJ (e) 143 kJ

A well-sealed room contains 60 kg of air at 200 kPa and 258C. Now solar energy enters the room at an average rate of 0.8 kJ/s while a 120-W fan is turned on to circulate the air in the room. If heat transfer through the walls is negligible, the air temperature in the room in 30 min will be (a) 25.68C (b) 49.88C (c) 53.48C (d) 52.58C (e) 63.48C

A 2-kW baseboard electric resistance heater in a vacant room is turned on and kept on for 15 min. The mass of the air in the room is 75 kg, and the room is tightly sealed so that no air can leak in or out. The temperature rise of air at the end of 15 min is (a) 8.58C (b) 12.48C (c) 24.08C (d) 33.48C (e) 54.88C

A room contains 75 kg of air at 100 kPa and 158C. The room has a 250-W refrigerator (the refrigerator consumes 250 W of electricity when running), a 120-W TV, a 1.8-kW electric resistance heater, and a 50-W fan. During a cold winter day, it is observed that the refrigerator, the TV, the fan, and the electric resistance heater are running continuously but the air temperature in the room remains constant. The rate of heat loss from the room that day is (a) 5832 kJ/h (b) 6192 kJ/h (c) 7560 kJ/h (d) 7632 kJ/h (e) 7992 kJ/h

A pistoncylinder device contains 5 kg of air at 400 kPa and 308C. During a quasi-equilibium isothermal expansion process, 15 kJ of boundary work is done by the system, and 3 kJ of paddle-wheel work is done on the system. The heat transfer during this process is (a) 12 kJ (b) 18 kJ (c) 2.4 kJ (d) 3.5 kJ (e) 60 kJ

A 6-pack canned drink is to be cooled from 188C to 38C. The mass of each canned drink is 0.355 kg. The drinks can be treated as water, and the energy stored in the aluminum can itself is negligible. The amount of heat transfer from the 6 canned drinks is (a) 22 kJ (b) 32 kJ (c) 134 kJ (d) 187 kJ (e) 223 kJ

A glass of water with a mass of 0.45 kg at 208C is to be cooled to 08C by dropping ice cubes at 08C into it. The latent heat of fusion of ice is 334 kJ/kg, and the specific heat of water is 4.18 kJ/kg8C. The amount of ice that needs to be added is (a) 56 g (b) 113 g (c) 124 g (d) 224 g (e) 450 g

A 2-kW electric resistance heater submerged in 5-kg water is turned on and kept on for 10 min. During the process, 300 kJ of heat is lost from the water. The temperature rise of water is (a) 0.48C (b) 43.18C (c) 57.48C (d) 71.88C (e) 1808C

1.5 kg of liquid water initially at 128C is to be heated at 958C in a teapot equipped with a 800-W electric heating element inside. The specific heat of water can be taken to be 4.18 kJ/kg8C, and the heat loss from the water during heating can be neglected. The time it takes to heat water to the desired temperature is (a) 5.9 min (b) 7.3 min (c) 10.8 min (d) 14.0 min (e) 17.0 min

An ordinary egg with a mass of 0.1 kg and a specific heat of 3.32 kJ/kg8C is dropped into boiling water at 958C. If the initial temperature of the egg is 58C, the maximum amount of heat transfer to the egg is (a) 12 kJ (b) 30 kJ (c) 24 kJ (d) 18 kJ (e) infinity

An apple with an average mass of 0.18 kg and average specific heat of 3.65 kJ/kg8C is cooled from 228C to 58C. The amount of heat transferred from the apple is (a) 0.85 kJ (b) 62.1 kJ (c) 17.7 kJ (d) 11.2 kJ (e) 7.1 kJ

The specific heat at constant volume for an ideal gas is given by cv 5 0.7 1 (2.7 3 1024 )T (kJ/kgK) where T is in kelvin. The change in the internal energy for this ideal gas undergoing a process in which the temperature changes from 27 to 1278C is most nearly (a) 70 kJ/kg (b) 72.1 kJ/kg (c) 79.5 kJ/kg (d) 82.1 kJ/kg (e) 84.0 kJ/kg

An ideal gas has a gas constant R 5 0.3 kJ/kgK and a constant-volume specific heat cv 5 0.7 kJ/kgK. If the gas has a temperature change of 1008C, choose the correct answer for each of the following: 1. The change in enthalpy is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine 2. The change in internal energy is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine 3. The work done is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine 4. The heat transfer is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine 5. The change in the pressure-volume product is, in kJ/kg (a) 30 (b) 70 (c) 100 (d) insufficient information to determine

An ideal gas undergoes a constant temperature (isothermal) process in a closed system. The heat transfer and work are, respectively (a) 0, cv DT (b) cv DT, 0 (c) cp DT, RDT (d) R ln(T2/T1), R ln(T2/T1) 4160 An ideal gas undergoes a constant

An ideal gas undergoes a constant volume (isochoric) process in a closed system. The heat transfer and work are, respectively (a) 0, cv DT (b) cv DT, 0 (c) cp DT, RDT (d) R ln(T2/T1), R ln(T2/T1)

An ideal gas undergoes a constant pressure (isobaric) process in a closed system. The heat transfer and work are, respectively (a) 0, cv DT (b) cv DT, 0 (c) cp DT, RDT (d) R ln(T2/T1), R ln(T2/T1)

Find out how the specific heats of gases, liquids, and solids are determined in national laboratories. Describe the experimental apparatus and the procedures used.

Someone has suggested that the device shown in Fig. P4163 be used to move the maximum force F against the spring, which has a spring constant of k. This is accomplished by changing the temperature of the liquidvapor mixture in the container. You are to design such a device to close sun-blocking window shutters that require a maximum force of 0.5 lbf. The piston must move 6 inches to close these shutters completely. You elect to use R-134a as the working fluid and arrange the liquidvapor mixture container such that the temperature changes from 708F when shaded from the sun to 1008F when exposed to the full sun. Select the sizes of the various components in this system to do this task. Also select the necessary spring constant and the amount of R-134a to be used.

You are asked to design a heating system for a swimming pool that is 2 m deep, 25 m long, and 25 m wide. Your client desires that the heating system be large enough to raise the water temperature from 20 to 308C in 3 h. The rate of heat loss from the water to the air at the outdoor design conditions is determined to be 960 W/m2 , and the heater must also be able to maintain the pool at 308C at those conditions. Heat losses to the ground are expected to be small and can be disregarded. The heater considered is a natural gas furnace whose efficiency is 80 percent. What heater size (in kW input) would you recommend to your client?

It is claimed that fruits and vegetables are cooled by 68C for each percentage point of weight loss as moisture during vacuum cooling. Using calculations, demonstrate if this claim is reasonable.

Using a thermometer, measure the boiling temperature of water and calculate the corresponding saturation pressure. From this information, estimate the altitude of your town and compare it with the actual altitude value.

Design an experiment complete with instrumentation to determine the specific heats of a gas using a resistance heater. Discuss how the experiment will be conducted, what measurements need to be taken, and how the specific heats will be determined. What are the sources of error in your system? How can you minimize the experimental error?