Vapour compression refrigeration system

The most important of all the refrigeration systems is the vapour compression refrigeration system, with the view point of commercial and domestic utility. This system is the most practical form of refrigeration.

Principle of Vapour compression refrigeration system

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In this system, Freon-12 or freon-22 is used as a refrigerant. This refrigerant is capable of rapid evaporation and condensation without leaving the plant. During the evaporation state, it absorbs heat from the heated body. This absorbed heat is used as latent heat to convert it from a liquid to a vapour state. In the condensation or cooling process, it rejects the heat to the external body. Thus, it produces a cooling effect on the working fluid.

Description of the Vapour Compression refrigeration system

The vapour compression refrigeration system consists of the following parts.

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Compressor:

The purpose of the compressor is to raise the temperature and pressure of the input refrigerant, which has low pressure and low temperature.

Discharge line:

A discharge line is used for delivering the high-pressure, high-temperature vapour from the discharge of the compressor to the condenser.

Condenser:

The temperature of the hot refrigerant is reduced by using a coolant with the help of a condenser.

Receiver tank:

A receiver tank is used to provide storage for condensed liquid so that a constant supply of liquid is available to the evaporator as required.

Liquid line:

A liquid line transmits the liquid refrigerant from the receiver tank to the refrigerant flow control.

Expansion valve:

The proper amount of refrigerant liquid into the evaporator is controlled by the expansion valve.

Evaporator:

An evaporator provides a cooling effect on the refrigerated space. The liquid refrigerant absorbs heat from the refrigerated surface and gets converted into refrigerant vapour.

Suction line:

With the help of the suction line, the low-pressure vapour from the evaporator is transferred to the suction inlet of the compressor.

Working principle of Vapour compression refrigeration system

A simple vapour compression system follows the following chain,

                 Compression – condensation – expansion – evaporation

The vapour at low temperature and low pressure enters the compressor where it is compressed, which makes the temperature and pressure increase considerably. From the compressor, the vapour enters the condenser where it is condensed to a very high pressure liquid and collected in a receiver tank. From the receiver tank, the refrigerant slowly passes through the expansion valve, where it is throttled down to a lower pressure. Finally, it reaches the evaporator where it extracts heat from the surroundings where it is being refrigerated and vaporizes into low pressure vapour. Thus the environment is cooled. From the evaporator, the low pressure refrigerant vapour enters the compressor. This process is repeated as a cycle.

Advantages of vapour compression refrigeration system

  • The running cost of this system is low.
  • For a fixed capacity of refrigeration, it is compact in size.
  • This is done for a large range of temperatures.
  • The size of the evaporator is small.
  • This system is available in a variety of sizes.

Disadvantages of vapour compression refrigeration systems

  • The cost of the refrigerant is high.
  • Refrigerant leakage is a problem.
  • The initial cost is high.
  • Energy consumption in the form of electricity is high.

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