Please help me.?

Question

I am currently studying for a physics test and I have come across a section on refrigerators and heat pumps. I do not understand how a refrigerator removes thermal energy from a colder body and adds it to a warmer body? Please respond with serious answers. Thanks

Answer 1

You have it backwards, a heat pump removes the heat from the refrigerator and sends it out the back. If you look behind your refrigerator you will notice a network of wires and tubes, if you touch them they will be warm, this is the heat that is taken from inside.

Answer 2

A refrigerator is a heat pump! It pumps heat from a lower level (lesser temperature inside) to a higher temperature (outside). How it does the job? There is a compressor, condensor and an evaporator inside the regrigerator. The refrigerant is a gas like Freon. When it is compressed, it heats up (adiabatic compression), and that heat is given outside by the condenser (the sides and the back of the regrigerator will be generally warm). Once the gas at higher pressure cools down, it may liquify. This is admitted through a throttle valve into the evaporator which is connected to the low pressure side of the compressor thus completing the feed-back loop. As the liquid expands inside the evaporator, it expands and the adiabatic expansion causes the temperature to drop (reverse of adiabatic compression). This cooled liquid/gas is used to remove heat from the food, water etc. inside the refrigerator.

In earlier models, you could see the deep freezer with fins going around it. That is the evaporator section. The compressor and the condenser are at the back.

The compressor runs on electricity.

There are other types of refrigeration cycles such as the ammonia-water (vapor absorption cycle) and thermoelectric refrigerators, but in all cases, the heat is pumped from a lower temperature to a higher temperature and hence needs energy.

Answer 3

Inside the compartment, a coolant (such as Freon) is allowed to vaporise in the coils, which sucks heat from the surroundings. You notice how if you let propane escape from the cylinder, frost forms around the valve? heat suck.

Outside the cooling compartment, a compressor turns the Freon back into liquid. The heat from this process is vented to the environment by radiation or whatever.