Basic Refrigeration Cycle

The cycle uses the Carnot Refrigeration cycle and operates as follows.

State 1 is the state after the refrigerant passes through an evaporator (D), where warm air heats the fluid and converts it completely to vapor.
State 2 is the state after the fluid passes through a compressor (A) which increases the fluid’s pressure and temperature up to superheated levels.
States 3 and 4 are when the fluid passes through an evaporator (B), which transfers heat to the ambient and condenses the fluid to liquid.
State 5 is the state after the fluid passes through an expansion valve or metering device (C), which lowers the pressure of the fluid. This cools the fluid and subsequently turns the liquid into a liquid/vapor mixture.