Heat Engines, Entropy, & the Second Law

Heat Pumps and Refrigerators


A heat engine run in reverse absorbs heat at a cold temperature and expels it at a hot temperature. This requires work to be input into the system. This describes the operation of a heat pump or a refrigerator.

Instead of describing the operation of a heat pump with the word efficiency, we use a very similar idea called the CoP or Coefficient of Performance

CoP = Qh/W

Gasoline Engine


Return to ToC

(c) Doug Davis, 2002; all rights reserved