Mechanical Engineering - Thermodynamics - Discussion

Heat rejection: Work done by surrounding on the system so heat will get rejected in compression.

Heat addition: Work done by a system on surrounding during expansion, so heat addition.

Answer is absolutely correct. I agree.

In isothermal compression, heat is added.

In an isothermal process, change in internal energy is zero as there is no change in temperature. So according to the first law of thermodynamics dQ = dW. During an isothermal compression process, volume decreases as pressure increases after compression. So the work in compression dW =P2V2 on(V3/V2).

As explained able volume after compression is less than volume before compression. Hence the dW term decreases as V3<V2.

Now, dW becomes negative, hence dQ is also negative. As we know that negative dQ means loss or ejection of heat. Hence heat ejection is taking place in an isothermal compression process.

It is isothermal compression. I agree with the given answer.

Agree with in isothermal expansion heat added & compression heat rejected.

In isothermal compression, if heat is added then how heat rejection takes place in isothermal compression. It doesn't make sense.

Please provide the correct answer with the explanation.

Heat rejection takes place in an isothermal expansion.

Isothermal expansion = isothermal heat addition or absorption.

Isothermal compression = isothermal heat rejection.