Freezers keep food cold. However, you will find that they become warm on the outside, which seems counterintuitive because they are cooling devices. So, do freezers have heat?
Freezers don’t produce heat. They suck heat from the food placed in them and pump it out, making the walls warm while their contents stay cold. The compressor also produces some heat, but it’s nominal. The heat on a freezer’s outside is from the contents in it and thermal leakage through the walls.
Let’s talk about this in more detail now.
Why Does A Freezer Get Hot On The Outside?
A freezer is an insulated box with a heat pump. Its main purpose is to keep its contents cold and prevent spoilage.
Now, the concept of keeping things cool is tricky because there is no such thing as “cold.” Cold is merely a lack of heat. In other words, you can say that things become cold when you remove heat from them.
A freezer has a heat pump. Its task is to suck heat from the inside of the compartment and transfer it outside.
This heat pump creates a very low internal temperature, below freezing point, to preserve the contents and prevent them from spoiling.
To create this low-temperature setting, the heat pump must remove any heat present inside the compartment.
Freezers work extra hard to eliminate all the heat inside their chamber and lower the internal temperature of the compartment.
So technically speaking, the freezer doesn’t produce heat. However, it pumps a lot of heat outside its chambers.
Recommended Further Reading:
- Do Mini Fridges Have Freezers? [How Do They Work?]
- How Many Amps Does A Freezer Use? (By Size And Type)
- Do Refrigerators Have Air Filters? (Where Are They Located?)
Where Does The Heat Inside A Freezer Come From?
The compressor unit and electric circuitry inside a freezer produce small, almost negligible quantities of heat. However, the outside of a freezer becomes quite warm. So, where is this heat generated?
Interestingly, the heat inside a freezer comes from the food inside it. The main task of the heat pump in the freezer is to suck this heat from the contents of the freezer and expel it.
By doing so, the freezer manages to lower the temperature and keep the food cold. Meanwhile, the removed heat goes out of the chamber through the walls, making them warm.
In an ideal situation, the freezer would have excellent insulation. Hot air from the environment should be unable to enter the appliance.
So, once the heat pump removes the existing heat, the walls should cool down. However, you may notice that the outside wall of a freezer remains warm most of the time.
This occurs because the interior of a freezer has some amount of heat. You may have introduced hot air into the freezer when you opened the door.
It’s also possible that the thermal insulation is less than ideal, and some heat enters the chamber from the outside.
Finally, friction caused by the operation of the compressor and other electrical parts can produce small amounts of heat.
The heat pump must continuously eliminate this heat to keep the chamber cold.
How Do Freezers Dissipate Heat?
To better understand how heat dissipation occurs in freezers, we should understand their basic principle of operation.
Refrigerators and freezers create a cooling effect by converting fluids from liquid to gas form and vice-versa.
You may already know that molecules are loosely bound together in liquids, whereas they are further apart and free to float in gases.
Now, to convert a liquid to vapor form, you must heat it. Heating makes liquids evaporate.
When you heat a liquid, the molecules break apart and move away from each other. This heat that makes a liquid transform into vapor is called latent heat.
Let’s next look at the reverse process and begin with a gas.
To convert gas into a liquid, you cool it. This process is called condensation, where you take heat away from the vapor. So, by taking the heat out of the gas, you end up with the liquid.
Now, refrigerators and freezers use this principle to operate. They have a fluid refrigerant, which is a liquid that easily evaporates.
The refrigerant fluid flows through coiled metal tubes called cooling pipes in the walls of your freezer. These pipes connect to a heat pump called the compressor.
The main job of the compressor is to suck the vapor from the cooling pipes. Due to this action, the liquid refrigerant changes into a gaseous form.
When the liquid changes to vapor, it takes heat out of the system. This keeps the inside of the freezer cool.
The vaporized refrigerant flows into a cooling pipe, where it condenses. As we mentioned earlier, condensation causes the vapor to return to liquid form. When the gas changes into liquid form, it releases heat.
Since these pipes are located at the back of the freezer, the heat is dissipated into the walls and hence the surrounding air. This is the heat you feel on the walls of the freezer compartment.
In other words, the heat pump inside a freezer sucks the heat from the freezer compartment and expels it to the surroundings. This makes the freezer cold and the inside of your kitchen warm.
By continuously performing this process, the freezer will keep the inner chamber cool at all times. So any item you place in it remains preserved below freezing point and doesn’t spoil.
Why Does Frost Build Up Inside A Freezer?
Frost build-up can reduce the storage space inside a freezer. Frost formation is troublesome because it prevents the door from closing properly.
Most modern freezers have frost-free features that prevent freezer frost from forming.
Freezer frost forms when moisture enters the freezer. It happens when you open and close the freezer door frequently.
Constant exposure to warm and moist air from the environment can cause moisture to creep in and form frost.
Frost formation will also happen if you accidentally leave the freezer door open. It will also happen if the gasket of the door is loose and doesn’t form a tight seal.
Another cause of freezer frost is a faulty thermostat or defrost heater. The appliance may fail to defrost properly when the thermostat or heater setting is wrong or malfunctioning.
Interesting Further Reading:
- Will Freezers Work In Cold Garages? [Which Freezers Work?]
- Do Freezers Use Freon? [How To Find Out If A Freezer Uses Freons?]
- Why Are Rice Cookers So Expensive? (Are They Worth It?)
Why Does The Outside Of A Freezer Seem Warmer Than That Of A Refrigerator?
Both refrigerators and freezers have a similar operating mechanism. These appliances work by pumping heat from the inside to the external environment, thus keeping the inner compartment cool.
Both appliances have heat pumps, refrigerant fluids, and cooling coils. However, the outside of a freezer may seem warm than that of a refrigerator.
This has to do with the temperature of the refrigerator and freezer compartments. Although refrigerators too cool their contents, they don’t achieve temperatures as low as freezers.
Freezers store food below freezing point. To achieve this low temperature, the appliance has to pump more heat to the outside.
A freezer appears to produce more heat because it has to create a cooler environment than a refrigerator.
Since it works harder to pump more heat out, the heat dissipated will also be higher. So the outer walls will appear to be warmer in a freezer than a refrigerator.