The Refrigerator

A refrigerator extracts heat from a system. Example: a kitchen refrigerator.

Again, to be useful, a refrigerator operates cyclically, with a certain amount of heat being extracted in every cycle.

Critical feature: two temperatures.

In a full cycle of a refrigerator, three things happen:

1. Work is done to compress a gas
2. Gas expands and removes heat Q_c from the interior of the refrigerator
3. The excess heat Q_h is delivered to the outside.

Schematics of a refrigerator:

Performance coeff:   κ ≡ Q_c/W = (Q_h/W)-1
Q_c = useful output
W = input energy