The principle of operation of refrigeration machines is based on the second law of thermodynamics. A certain amount of work has to be done to transfer heat from a cold body to a hot body.
The second law of thermodynamics is mathematically expressed as
Qk =Q0+L, J;
(Qk = Q0+AL, kcal),
Where Qk is the quantity of heat transferred to the hot body;
Q0is the quantity of heat given out by the cold body;
L is the work done to transfer the heat;
A=1/427 is the heat equivalent of work.
Machines that gather heat from a cold body and give it to a hot body are called refrigeration machines. Heat is transferred form a body at a lower temperature to a body at a higher temperature by a working substance (fluid) circulating in the refrigeration machine..............