How does a freezer work?

Written by john lister Google
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How does a freezer work?
A freezer takes advantage of evaporation. (Joe Raedle/Getty Images News/Getty Images)

A freezer uses electrical motors to repeatedly turn a gas into liquid and back again. This process causes changes in temperature which in turn keep the food compartment below zero degrees Celsius, the freezing point of water. This causes the water in food to freeze, which keeps the food itself in edible condition for longer.

Evaporation principle

The principle of a freezer is based on evaporation, in which a liquid becomes hotter and turns into a gas; it's a more gradual alternative to boiling. This process absorbs heat causes the area around the liquid to cool down, something you'll notice if you splash water on yourself on a hot day. The temperature at which a liquid evaporates depends on the starting temperature of the liquid, the volume and surface area or the liquid, the surrounding air temperature, and the ordinary boiling point of the liquid. The evaporation point of water is nearly always too high to leave the surrounding air cold enough to freeze food.


Instead of water or other substances that are liquid at room temperature, fridge freezers usually use substances that are gas at room temperature. Common examples include isobutane and tetrafluoroethane. Some other gases used in the past, included those known as CFCs, are no longer used because they cause too much environmental damage.


A freezer has a device known as a compressor that raises the air pressure in a gas container (thus compressing the gas), which eventually turns the gas into liquid. The heat from this process is dispersed into your kitchen through metal coils at the back of the freezer. The gas then pumped into another area, the expansion valve, with a lower air pressure. This causes it to turn back into gas through evaporation, causing the surrounding pipes (and in turn the freezer compartments) to get extremely cold. The electricity in a freezer is simply used for the motor mechanics of the compressor and for using a thermostat to start and stop the process to regulate temperature.

Freezer vs fridge freezer

A fridge freezer is simply a device that has two separate compartments, one a refrigerator and one a freezer. Generally the freezer sections in these devices do not get as cold as with a standalone freezer. This is because both compartments use the same loop for the coolant gas, meaning there's only so cold the freezer compartment can be made before it becomes more difficult and less economical to keep the refrigerator section above freezing point.

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