Question

(a) Which might describe a heat engine? 

(b) Which might describe a heat pump? 

(c) Which might describe a refrigerator? Explain.

The figure shows PV diagrams for five cyclical processes. (Cycle D is a simplified model of a steam engine cycle.)

Answer 1

(a)

Heat engine converts heat into work and the cycle operates in the clockwise direction consisting of thermodynamic processes that are repeated in the same way. The processes B and D describe heat engine as the cycle in these processes move in clockwise direction.

 

(b)

Heat pumps pump heat from the colder outdoors into the warmer house. The energy transfer will be in a direction opposite to the heat engine. Therefore the processes A, C, and E describe heat pump as the cycle in these processes move in the counterclockwise direction.

 

(c)

Refrigerators pump the heat out of the food compartment into the warmer room. The work of refrigerator will be similar to the heat pump. Therefore the processes A, C, and E describe refrigerator as the cycle in these processes move in the counterclockwise direction.