Vapour Compression Refrigeration System
The following are the basic parts of a vapour compression refrigerator:
- Expansion valve
The Figure shows the layout of a Vapour Compression Refrigeration system.
At the beginning of the refrigeration cycle, the refrigerant (Freon-12, in the case of domestic refrigerator) leaves the receiver (storage tank) under high pressure. It travels through pipes to the expansion valve. The pipes are usually made of copper.
2) Expansion Valve
It is also called as expansion device or throttle valve. The pressure of the liquid passing through this device drops. When the pressure drops, the temperature also drops. This is because when the pressure drops the molecules loose energy resulting in a drop in temperature. This effect is called “Joule – Thomson effect’
The low pressure, low temperature liquid refrigerant, passes to the evaporator. The low temperature liquid absorbs the heat from the evaporator and cools the substance in the evaporator. It is the coldest region in the refrigerator and serves as the freezing unit. By absorbing the heat, the liquid refrigerator becomes vapour by the time it leaves the evaporator
The low pressure, low temperature vapour from the evaporator enters the com pressor. The compressor compresses the refrigerant vapour, as a result of which the pressure and temperature of the vapour increases. Thus the compressor performs work on the refrigerant.
The high temperature, high pressure vapour enters the condenser. The outer sur face of condenser tube is in contact with the atmospheric air. This air receives heat from high temperature vapour inside the condenser. The vapour gets cooled, and thus condenses to liquid. This liquid refrigerant flows back to the Receiver (storage tank).
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