2.3 The basic cycle in a log Ph diagram

​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.

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