How does a freezer freeze stuff?
#62022. Asked by Pyro900. (Jan 26 06 6:53 PM)
Here goes an attempt at an explanation. Wish me luck...|
A freezer is basically an insulated food cupboard with a heat=pump attached.
The heat-pump has a coil of tubing at the back which passes into the freezer and back out again.
The tube contains a gaseous refrigerant which is compressed into a liquid (by a compressor) as the tube exits the freezer.
By squidging the refrigerant into a liquid, the heat in it is also squidged into a smaller volume so the heat is more concentrated and the tube gets hot.
Now you know that if you put something hot next to something cooler, the heat flows away from it. The coil of tubing has a lot of surface area helping it to lose heat to the air.
By the time the liquid has coiled round the tube and back into the freezer it has already started to expand into a gas again. This gas now has a lot less heat per unit volume that it did before it left the freezer, so is colder than the air inside the freezer. The tube therefore draws heat from the air to restore the balance.
As the tube exits the freezer, the gas is compressed into a liquid and the cycle begins again. The air heated at the back can escape and take the heat with it, and this is assisted by fans. The air inside the fridge is sealed in so gets colder and colder each time the refrigerant draws heat from it. Eventually, the temperature of the compressed refrigerant and the air reach an equilibrium temperature and cannot be cooled further.
In a freezer, this is less than 0 deg C and in a fridge it is a little higher.
Note that the compressor and fans are very energy thirsty and fridges and freezers use an average of one third of a domestic supply.
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