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How does a domestic refrigerator work?

Updated: Category: How things work
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This article explains the construction and working of a domestic home refrigerator. You will know details about the principal parts of any domestic refrigerator, namely evaporator, compressor, condenser and capillary tube. A domestic refrigerator works on vapor compression refrigeration cycle.

To preserve foods/vegetables and drink cold waters, we normally rely on domestic refrigerator but do you know how does this machine work? Actually domestic refrigerator is a heat pump which throws the heat of the foods or stuffs to be cooled to atmosphere by taking power of compressor. Second law of thermodynamics with its Clausius statement suggests, to throw heat from low temperature to high temperature, one must put extra efforts in form of work. The same is done by compressor in domestic refrigerator.

The domestic refrigerator works on 'Vapor Compression Refrigeration Cycle (VCRC)'. The basic working of the cycle is explained as follows.

Construction of domestic refrigerator

The vapor compression cycle consists of 'Evaporator', 'Compressor', 'Condenser' and 'Capillary tube' as main parts. The system works on closed cyclic operation with the help of heat transfer media called 'refrigerant'. This refrigerant changes the phase during passing through evaporator and condenser to exchange the heat.

Working of domestic refrigerator

The function of compressor is to raise the pressure of gaseous refrigerant coming from the evaporator. By raising the pressure, boiling point of the refrigerant increases. This high pressure and high temperature refrigerant while passes through the condenser, changes the phase and condenses in high pressure and temperature liquid refrigerant. The room air is at lower temperature than the refrigerant passing through the condenser, hence condensation takes place and vapor refrigerant converted to liquid refrigerant. Thus heat is thrown to the air at this point in the refrigerator. Now resultant liquid refrigerant which is at high pressure and temperature, passes through the capillary tube which is made up of copper material and has very small diameter and longer length. As the high pressure liquid refrigerant passes through the capillary tube, due to throttling effect, temperature and pressure of the refrigerant decreases. Majority of the cooling is produced at this point in refrigerator. This low temperature and low pressure refrigerant now passes through evaporator where refrigerant in liquid phase takes heat from foods and stuffs. At this point, boiling point of liquid refrigerant is very low (because of low pressure) in terms of -20 degree C. Thus anything above this temperature makes refrigerant to boil. This low pressure vapor again circulated to compressor and cycle continuously as long as compressor is in running condition. (NOTE: Boiling point of refrigerant is a function of pressure, Thus change in pressure in compressor and capillary makes it to be able to change the phase).

Some technical Points of Domestic refrigerator

  • Compressor used in domestic refrigerator is of reciprocating type and is of hermetically sealed means compressor and electric motor are a single unit enclosed in a container

  • Capillary tube is a simple copper tube having very less diameter in few millimeter and longer length in terms of few feet. This low diameter and higher length increases friction and this is the reason why high pressure liquid refrigerant is converted to low pressure one due to pressure drop in capillary itself.

  • Except compressor, there are no moving parts in domestic refrigerator, this is the reason why refrigerator lasts long

  • Condenser and evaporator are simply heat exchangers where refrigerator changes the phase by rejecting and accepting heat from condenser and evaporator respectively. The compressor and capillary tube change the pressure accordingly to get boiling point in range to be able to change the phase

  • Refrigerator capacity is defined in 'Litre'. The litre is volume of storage space.

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