A refrigerator is a heat extraction machine that keeps food fresh. At room temperature hot drinks cool but ice cubes also melt. That happens because heat usually travels from one hot place to a cool place. Refrigerators reverse the flow of heat. In refrigerators, heat is moved from the inside and released at the back. The interior of the refrigerator gets cold and stays cold so that food stays fresh and ice cubes stay frozen. A refrigerator contains two connected pipes through which a substance known as a refrigerant is pumped. As a refrigerant circulates around a fridge it alternatively evaporates and condenses. Liquid refrigerant passes through the first pipe (the condenser) through a tiny hole into the second pipe (the evaporator). After that the high pressure causes the refrigerant in vapor form to condense giving out heat at the back of the refrigerant as it liquefies.

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Figure 1: A picture showing the refrigerator system

Evaporation and Condensation
Figure 2: A picture showing 1 part of the refrigeration system
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Liquid turns into vapor by the process of evaporation. Vapor turns into liquid by the process of condensation. Inside a refrigerator the refrigerant evaporates and condensates to get through each of the two pipes. The refrigerant in vapor form is compressed in a compressor and turned into a cold liquid by condensation. The compressor is at the bottom of the refrigerator and is powered by an electric motor.

Refrigerant- A substance that runs through a refrigerator.
Alternatively- Switches from one to another.
Liquefies- To make or become liquid.

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