How your fridge works

This is a diagram of how a basic mechanical refrigeration cycle works.
If you hover your mouse pointer over the different parts of the diagram an explanation of what is happening will appear.
Definitions of some of the terms used can be found below the diagram.

You can see the refrigerant moving around the circuit at different temperatures. Think about what happens when it expands or contracts. What effect does this have on the temperature?

Elements

Evaporator The cold liquid absorbs heat from the air in the fridge, chilling the inside of the fridge. The liquid vapourises.
Compressor The vapour is compressed, bringing it to a higher temperature.
Condenser Allows the gas to cool and liquify, and to release this heat through ventilation fins on the back of the fridge. As the heat is removed the gas condenses to a liquid.
Expansion device The flow of the liquid is controlled and pressure is lowered so that some of the liquid turns into a vapour. This evaporation cools the remaining liquid.
Ventilation fins Heat from the condenser is released through the ventilation fins on the back of the fridge.


Definitions

Absorption A process in which energy (heat) is taken up by a liquid or solid.
Compressor This is a pump which compresses refrigerant gas, and consequently heats the gas.
Condensation A change of state from gas or vapour to liquid.
Evaporation A change of state from solid or liquid to gas or vapour. It occurs when some molecules of a liquid have enough energy to escape into the gas phase and this has an overall cooling effect on the liquid.
Expansion The increase of volume of a sample of substance.
Intermediate temperature A temperature somewhere between hot and cold.
Refrigerant A chemical substance used as a fluid in a refrigeration system. There are many different types of fluid used, depending on the system design. Most commonly used are hydrofluorocarbons (HFCs) and hydrocarbons (HCs).
Refrigeration This is the transfer of heat from a substance to be cooled to somewhere else. Heat flows naturally from a warm substance to a colder one eg fish can be cooled by surrounding it with packing ice.
Restrictor Something that restricts the flow of a gas or liquid.
Sublimation This is when a solid turns to vapour without going through the liquid phase. For example, you can see solid carbon dioxide (CO2) turning to vapour when it melts without producing a liquid (dry ice).
Thermal Insulation A means of preventing or reducing the transfer of thermal energy (heat). Good insulators are foam, wool, and vacuums.
Vapour A substance in a gas state that has reached a temperature at which it could become a liquid just by the application of pressure. It is usually still in contact with the liquid from which it was formed.
Ventilation The addition of fresh air.

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