Question

air contained in a cylinder comprises the system. a cycle is completed as follows: piston does 85 kj of work on air during compression stroke while 42 kj of heat is rejected to the surroundings. during expansion stroke air does 120 kj of work on the piston. determine the heat transfer

Answer 1

The heat transfer during the expansion stroke is 163 kJ

According to the first law of thermodynamics for a cycle the net heat transfer in the system is equal to the net work done.

Therefore, the heat transfer during the expansion stroke is calculated as

(Q-W)_{compression)=(Q-W)_{expansion}

(-42-(-85)=(Q-(120))

Q=163 kJ

Therefore the heat transfer during the expansion stroke is 163 kJ