Figure 2.8 shows the fundamental process that describes the ideal refrigeration cycle. The following are assumed for the fundamental process:
- No sub-cooling of the liquid or superheating of the gas
- Ideal compression, i.e. it occurs at constant entropy
- No pressure drop losses
The fundamental process can be divided into the four parts described below, the numbers referring to the numbers in Figure 2.8:
- (1-2): The compression is performed at constant entropy.
- (2-3): The condensation is performed at constant pressure and thus follows the isobars.
- (3-4): The lowering of the pressure is performed at constant enthalpy (h).
- (4-5): The evaporation is performed at a constant pressure and thus follows the isobars, i.e. the pressure at states 1 and 4 is equal to the evaporator pressure (temperature). State 1 is determined by the temperature of the gas leaving the evaporator.