As the refrigerant circulates through the system, it passes through a number of changes in state or condition, each of which is called a process. The refrigerant starts at some initial state or condition, passes through a series of processes in a definite sequence, and returns to the initial-condition. This series of processes is called a cycle.
The simple vapour- compression, refrigeration cycle is made up of four fundamental processes:
(1) expansion,
(2) vaporization,
(3) compression, and
(4) condensation.
To under-stand properly the refrigeration cycle it is necessary to consider each process in the cycle both separately and in relation to the complete cycle. Any changes in any one process in the cycle will bring about changes in all the other processes in the cycle.
