For each of the following statement, choose \"T (True) or \"F\" (False) 1. A hea

Question

For each of the following statement, choose "T (True) or "F" (False) 1. A heat engine with a 100% efficiency is impossible to build because it violates the first law of thermodynamics. 2. Entropy generation is a state property 3. If a process is both adiabatic and reversible, then the process is also isentropic 4. For an expansion process, the boundary work is positive. 5. Entropy per unit mass and specific heat have the same dimension. 6. The compressibility factor Z-Pv/(RT) for an ideal gas is always 1 7. Turbine is a device that transfers mechanical energy into flow energy 8. It is possible to compress an ideal gas isothermally in a piston-cylinder device. 9. Consider two identical fans, Fan A at sea level and Fan B on top of a high mountain, running at identical speeds. The mass flow rate of Fan A is higher than that of Fan B 10.One incorrectly uses the "ratio of the volume of the saturated vapor to the total volume" to calculate the quality, so his/her result is larger than the real quality

Explanation / Answer

1) False

First law of thermodynamics deal with only energy conversion.

It is second law of thermodynamics, which deny the possibility of converting complete heat into work, it says that there is always energy rejection associated with heat engines, thus no heat engine is 100%v efficient,

2) True

Entropy is a property of the system and it tells us how far the system has deviated from the ideal or reversible state. It tells about system dis-orders. It is the ratio of heat transferred to temperature.

3) True.

If the process is both reversible, that is system is capable of acquiring initial state without leaving any trace of the process had occurred and adiabatic, that is no heat interactions, the process is called isentropic and entropy of the process is constant.

4) True.

yes, in case of the expansion process, work is done by the system on surroundings. It is arbitrarily taken as positive. In case of compression, work is done on the system and the sign is negative.

5) True

Entropy per unit mass = e = (Q/T)/m = J / kg-K.

Specific heat = C = Amount of heat required to cause a unit change in temperature = J / kg-K.

6) True

the ratio of the actual volume of a real gas to the volume predicted by the ideal gas at the same temperature and pressure as the actual volume. For an ideal gas, Z always has a value of 1

7) False

Turbine is a device where we get mechanical energy at the expense of flow energy. Turbines are usually attached to shafts which will rotate as flow work is done on the turbine.

8) False

From ideal gas law, PV=RT, keeping it as Isothermal which means temperature constant, for an ideal gas it is not possible.

9) True.

The density of air at sea level is higher than the density of air on top of a high mountain. Therefore, the volume flow rates of the two fans running at identical speeds will be the same. Since mass flow rate depends on the density, due to the density difference mass flow rate of the fan at sea level will be higher.

10) False.

It depends upon the choosen volume of saturated from real value.

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