Process of VCRS:

Process 1-2: lsentropic compression of saturated vapour in compressor

Process 2-3': Isobaric heat rejection in condenser

Process 3'-3: Sub-cooling (Under cooling)

• Sometimes, the refrigerant,after the condensation process 2-3', is cooled below the saturation temperature (T_3') before expansion by throttling.
• Such a process is called under-cooling or sub-cooling of the refrigerant.
• The refrigeration effect ls Increased due to sub-cooling.
• The ultimate effect of the under-cooling is to increase the value of the coefficient of performance under the same set of conditions.
• The process of under-cooling is generally brought about by circulating more quantity of cooling water through the condenser or by using water colder than the main circulating water.
• Sometimes, this process is also brought about by employing a heat exchanger.
• The magnitude of sub-cooling is usually kept between 5 to 10 K.
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Process 3-4: lsenthalpic expansion of saturated liquid in throttling device

Process 4-1: Isobaric heat extraction in the evaporator.