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Reviewing ConceptsFor review, complete the following:(a)
Chapter 4, Problem 94P(choose chapter or problem)
For review, complete the following:
(a) Answer the following true or false. Explain.
(i) For a one-inlet, one-exit control volume at steady state, the mass flow rates at the inlet and exit are equal but the inlet and exit volumetric flow rates may not be equal.
(ii) Flow work is the work done on a flowing stream by a paddlewheel or piston.
(iii) Transient operation denotes a change in state with time.
(iv) In this book the flow at control volume inlets and exits is normally taken as one-dimensional.
(v) Where mass crosses the boundary of a control volume, the accompanying energy transfer is accounted for by the internal energy of the mass only.
(b) Answer the following true or false. Explain.
(i) A diffuser is a flow passage of varying cross-sectional area in which the velocity of a gas or liquid increases in the direction of flow.
(ii) The human body is an example of an integrated system.
(iii) When a substance undergoes a throttling process through a valve, the specific enthalpies of the substance at the valve inlet and valve exit are equal.
(iv) The hot and cold streams of cross-flow heat exchangers flow in the same direction.
(v) The thermodynamic performance of a device such as a turbine through which mass flows is best analyzed by studying the flowing mass alone.
(c) Answer the following true or false. Explain.
(i) For every control volume at steady state, the total of the entering rates of mass flow equals the total of the exiting rates of mass flow.
(ii) An open feedwater heater is a special type of a counterflow heat exchanger.
(iii) A key step in thermodynamic analysis is the careful listing of modeling assumptions.
(iv) An automobile’s radiator is an example of a crossflow heat exchanger.
(v) At steady state, identical electric fans discharging air at the same temperature in New York City and Denver
will deliver the same volumetric flow rate of air.
Questions & Answers
QUESTION:
For review, complete the following:
(a) Answer the following true or false. Explain.
(i) For a one-inlet, one-exit control volume at steady state, the mass flow rates at the inlet and exit are equal but the inlet and exit volumetric flow rates may not be equal.
(ii) Flow work is the work done on a flowing stream by a paddlewheel or piston.
(iii) Transient operation denotes a change in state with time.
(iv) In this book the flow at control volume inlets and exits is normally taken as one-dimensional.
(v) Where mass crosses the boundary of a control volume, the accompanying energy transfer is accounted for by the internal energy of the mass only.
(b) Answer the following true or false. Explain.
(i) A diffuser is a flow passage of varying cross-sectional area in which the velocity of a gas or liquid increases in the direction of flow.
(ii) The human body is an example of an integrated system.
(iii) When a substance undergoes a throttling process through a valve, the specific enthalpies of the substance at the valve inlet and valve exit are equal.
(iv) The hot and cold streams of cross-flow heat exchangers flow in the same direction.
(v) The thermodynamic performance of a device such as a turbine through which mass flows is best analyzed by studying the flowing mass alone.
(c) Answer the following true or false. Explain.
(i) For every control volume at steady state, the total of the entering rates of mass flow equals the total of the exiting rates of mass flow.
(ii) An open feedwater heater is a special type of a counterflow heat exchanger.
(iii) A key step in thermodynamic analysis is the careful listing of modeling assumptions.
(iv) An automobile’s radiator is an example of a crossflow heat exchanger.
(v) At steady state, identical electric fans discharging air at the same temperature in New York City and Denver
will deliver the same volumetric flow rate of air.
ANSWER:Step 1 of 3
Part a
(i) Volumetric flow depends on the area of cross-section on the inlet and exit. So, it may be different depending on their cross-section. But at the steady state, the mass flow rates are equal.
So. the given statement is true.
(ii) The work required to push a fluid into an inlet and out of an exit is the flow work.
So, the given statement is false.
(iii) If the state of an operation changes with time, it is known as the transient state.
So, the given statement is true.
(iv) The given statement is true.
(v) When a mass crosses a boundary, potential and kinetic energy are also transferred across the boundary.
So, the given statement is false.