Working principle of Vapour Compression Refrigeration System

How does a Vapour Compression Refrigeration System work ?

v The main components of vapour compression system are

1. Compressor

2. Condenser

3. Expansion valve

4. Evaporator

v Compressor – It is used to increase the pressure of refrigerant from evaporator pressure to condenser pressure. For low pressure application reciprocating compressor is used. For very high pressure application, centrifugal compressor is used.

v Condenser – The main function is to condensate the vapour refrigerant into liquid refrigerant. In household, air cooled refrigerant is used. For industrial applications water and liquid cooled refrigerant is used.

v Expansion valve – It is used to control the flow rate. It makes partial evaporated liquid refrigerant to evaporator pressure.

v Evaporator – It is used to evaporate the refrigerant by transferring the heat from the area to be cooled.

v Process 1-2 – Pressure of the vapour refrigerant is increased by compressor adiabatically.

v Process 2-3 – Vapour refrigerant is condensed to the liquid through heat transfer.

v Process 3-4 – Liquid refrigerant expands to the evaporator pressure. Also flow of liquid refrigerant is controlled by means of expansion valve.

v Process 4-5 – Partially vapored refrigerant is evaporated through heat transfer from area to be cooled.

v Refrigeration effect by refrigeration system (Output) ∆h = m C_p dT = h₁ – h₄

v Work done by the compressor (Input) ∆h = m C_p dT = h₂ – h₁

v Substituting in COP formula

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