Question

2. Understand how much work and heat are transferred in an ideal heat engine or reverse heat engine.

a) What is the maximum work that I can get from a heat source at 450K and a cold sink at 298K? (0.338 J per joule of heat in at 450 K)

b) How much heat can I get from ideal reverse heat engine per Joule of energy of work if the outside temperature is 10oC and my house is at 25oC? (approx. 20 J)

Answer 1

a)

For ideal heat engine

the efficiency is giveen by

efficiency is nothing but net work done per joule of heat supplied

Hence the maximum amount of heat that can be done is 0.338 Joules of work per Joule of heat supplied

b) Here for reverse heat enginer we don't have efficiency term but rather COP term

COP is given by

.

Hence reverse heat engine will extract 20 Joule of heat per Jule of work done to the system