Question Set 77

1.What is the difference between scavenging and supercharging ?

Ans: Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air.

2.What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.

Ans: Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.

3.In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?

Ans: It will decrease.

4.Why entropy change for a reversible adiabatic process is zero ?

Ans: Because there is no heat transfer in this process.

5.What are two essential conditions of perfect gas ?

Ans: It satisfies equation of state and its specific heats are constant.

6.Enthalpy and entropy are functions of one single parameter. Which is that ?

Ans: Temperature.

7.Why rate of condensation is higher on a polished surface compared to rusty surface ?

Ans: Polished surface promotes drop wise condensation and does not wet the surface.

8.How much resistance is offered to heat flow by drop wise condensation ?

Ans: Nil

9.What is the relationship between COP of heating and cooling ?

Ans: COP of heating is one(unity) more than COP of cooling.

10.How much is the work done in isochoric process ?

Ans: Zero.