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How Does a Freezer Work?

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By Elizabeth Masterman

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Most of us have a freezer, with many of us relying on our freezer to make our lives easier. It’s the hardest working appliance in the home, being the only appliance that is rarely, if ever, switched off. But have you ever wondered how it actually works?

How Does a Freezer Work?

Freezers rely on the idea that a gas, when condensed into a liquid, will release heat, and when it evaporates, it absorbs heat. Most freezers function by passing refrigerant through a system that compresses, condenses and evaporates it to remove heat from inside the unit.

How Does a Freezer Freeze Food?

When the air in the freezer is sufficiently cold, this will cause the food to freeze. The water in the cells of the food will turn into ice crystals.

Ideally, you want the food to freeze quite quickly as if it freezes slowly, it is more likely to develop larger ice crystals, which can affect the texture of the food.

This is why vegetables with a high water content, like lettuce and celery, don’t freeze well, as the large crystals burst the cell walls and turn to mush.

Frozen Vegetable Mix

How Does a Deep Freezer Work?

The term ‘deep freezer’ was used to refer to a freezer that reached a colder temperature and had a faster freezing process, but nowadays, the term is used to refer to any standalone freezer, as opposed to a combined fridge freezer. 

Technically, there isn’t a starting point to the process, as it’s a cycle, but we’ve got to begin somewhere, so let’s begin with the refrigerant as a vapour under low pressure.

Firstly, the refrigerant goes through the compressor, usually at the bottom and towards the back of the freezer. As the name suggests, the compressor compresses the vapour, heating it and pressuring it.

At this point, the hot vapour enters the condensing coils, usually on the back of the freezer. These pipes are exposed to the air, meaning most of the heat can escape into the room, and the refrigerant reverts to its liquid state.

This warm liquid then passes through a capillary tube or an expansion valve, before entering the larger space of the evaporator coils inside the freezer.

This causes the pressure to drop suddenly, causing the liquid to expand rapidly and boil, then evaporate.

Evaporation is an endothermic process, absorbing heat from the air inside the freezer, causing the temperature inside the freezer to fall.

The vapour in the evaporator coils then returns in its low-pressure state back to the compressor, to begin the process again.

How Does a Chest Freezer Work?

A chest freezer is a large type of deep freezer with the door on top, and so works in the same way.

While a fridge freezer or a standalone freezer usually stands in the kitchen for ease of access, chest freezers are often kept in a utility or garage and are opened less frequently.

Chest freezers are great for long-term storage. They can store vegetables if you have a vegetable patch or allotment.

They can also be helpful to store large quantities of meat, for example, if you buy your meat in bulk from a butcher or if you own a farm or smallholding. They are also great for larger items, like the Christmas turkey. 

Chest Freezer

How Does a Fridge Freezer Work?

A fridge works in precisely the same way as a freezer, just at a higher temperature, so a fridge freezer works in a very similar way to a deep freezer.

Some fridge freezers operate on one system, while others have a separate system for each part – the fridge and the freezer.

How Does a Frost-Free Freezer Work?

Every time you open the door to your freezer, warm air enters the appliance. This air contains moisture, which will then freeze and become frost.

Frost can build up, not only taking up valuable space, but it can also cause problems with your freezer.

It can stop the door from closing properly, which will stop the freezer being able to function correctly.

Plus, if there is a build-up of frost in your freezer, it will mean your freezer has to work harder and can cause damage to your freezer if left too long.

However, defrosting your freezer can be an inconvenient and time-consuming job, so many modern freezers are frost-free. If you have a frost-free freezer, there are a few ways it could achieve this function.

As mentioned above, every time you open your freezer, the warmer air from outside the freezer enters the unit. Some frost-free freezers have a fan that removes this warm air before the moisture in the air has a chance to condense and freeze.

Other frost-free freezers use a heating coil wrapped around the evaporator coils.

Every few hours a defrost sensor or a timer switches on the heating coil until the ice is melted, and then a temperature sensor switches the heater back off again. 

How Do Portable Fridge Freezers Work?

Portable fridge freezers are great for picnics, camping or outdoor adventure. They offer all the benefits of a regular fridge freezer but in a smaller and more robust unit.

A portable fridge freezer works in the same way as a static freezer.

However, the condenser coils are within the unit to keep them protected, rather than exposed on the back of the appliance.

For this reason, the unit will have vents to allow the warm air to escape, and you must take care not to cover these vents otherwise the unit won’t function effectively and could pose a fire risk.

Do you have more questions about how a freezer works? Then check these out:

What are the Components of a Freezer?

The four main parts of a freezer are the compressor, condenser coils, capillary tube and evaporator.

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