The boundary work associated with a constant volume system is always zero. The c

Question

The boundary work associated with a constant volume system is always zero. The cross-sectional area of a nozzle always decrease in the flow direction. In a turbine where the stream first enters, the turbine blades are usually the largest. From the conservation of mass principle, it can be shown that the density of air entering a compressor is equal to the density of air exiting. A heat pump can operate both as a heater in the winter and an air conditioner during the summer. Evaporation is a cooling process. Condensation is a heating process. A thermocouple is an example of the Peltier effect. In Jesie's experiments he showed that for an ideal gas that internal energy is function of both temperature and pressure. One would expect the temperature of air to drop as it under goes a steady flow throttling process.

Explanation / Answer

1) True , Because boundary work is given by Pdv , hence when dv = 0   work = 0

2) False , cross sectional increases in case of a diverging nozzle.

3) False , turbine blades are larger at the exit because the cross sectional area at the exit is larger than inlet.

4) False , Density of air can change only the mass flow rate is constant.

5) True, A heat pump can be used to perform both functions.

6) True, Evaporation does always lead to cooling due to absorption of heat.

7) True, Condenstation of a substance releases heat.

8) False, thermocouple is not an example of peltier effect

9) False, internal energy is a function of temperature.

10) False, throttling process may also lead to heating of air as well.

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