Working of Refrigerator and Refrigeration Principle
Earlier food was preserved by traditional methods like salting and pickling which were not always practical. Nowadays refrigerators are used to preserve food.
They are able to preserve food for long periods by keeping it cool.
This cooling process prevents bacteria from attacking and spoiling the food, which in turn reduces wastage of food.
A Refrigerator works on 2 basic principals
1) As a liquid evaporates , it absorbs the heat from the surrounding areas . (A example, after having a bath , if you stand in the sun , you feel cold because the water is evaporating and absorbing the heat from your body.)
2) The opposite occurs if gas is compressed. That is a gas gives out heat when it is changed into a liquid. ( An example , A cycle pump gets hot while filling air into a cycle tire , because air is getting compressed).
6 Parts of a Refrigerator
1. Heat exchanging pipes – These coils are present on the inside and the outside of the fridge , they carry the refrigerant from one part of the fridge to another.
2. Refrigerant – This is the substance which evaporates in the fridge causing freezing temperatures.
3. Expansion Valve – The expansion valve which is made up of a thin copper coil reduces the pressure on the liquid refrigerant.
4. Compressor – A compressor is a metal object which compresses the refrigerant thus raising the pressure and in turn the temperature of the gas.
5. Condenser – A condenser , condenses , that is , it converts the refrigerant into liquid form , reducing its temperature.
6. Evaporator – A evaporator absorbs the heat in the refrigerator with assistance of the evaporating liquid refrigerant.
How Refrigerators work?
- The refrigerant gas is compressed to a high pressure which results in rise of temperature.
- This gas then passes through heat exchanging pipes where it loses most of its heat to its surroundings which causes the cooling of the refrigerant.
- It then passes through a condenser which causes the gas to get converted into a liquid form. This happens because In this condenser the temperature of the refrigerant keeps on reducing but the pressure remains the same.
- The refrigerant then reaches the expansion valve, where there is a drastic decrease in pressure which causes the refrigerant to expand and evaporate.
- This further decreases the temperature.
- The evaporation of the refrigerant takes place in the evaporator, which absorbs the heat from the food and the air in refrigerator which keeps the food cool.
- The second law of thermodynamics is used here.
- This law states : When 2 surfaces of different temperatures come in contact with one an the other , the surface with the high temperature cools and that with the lower temperature heats up.
- This causes the refrigerant to again heat up to form gas. This gas then again enters the compressor and the whole process is repeated again.
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