The compressor gets hot for a couple of reasons:
1) There's a motor inside there. Running all the time, it's going to get warm. Running all the time in a warm room, it's going to get warmer. Running constantly trying to cool down a fridge whose door is standing open, it's going to get very warm...
Best answer: The compressor gets hot for a couple of reasons:
1) There's a motor inside there. Running all the time, it's going to get warm. Running all the time in a warm room, it's going to get warmer. Running constantly trying to cool down a fridge whose door is standing open, it's going to get very warm indeed.
2) The refrigerator works by pushing heat. Imagine:
Do you remember pumping up a bicycle tire with a bike pump? And the bottom of the pump got hot? That's because of the compression of the air - the heat energy in the air (there's heat energy everywhere) gets squashed into a smaller space. Taking up less space but having the same energy as it had before means it has to feel hotter.
Now imagine the propane tank on the gas grill while the grill is on. That tank starts to get pretty cold, right? Even frosty sometimes. It's because the propane inside is boiling into gas - yes, boiling just at room temperature - and carrying heat away. And when heat is carried away, what's had its heat carried away feels cold.
Refrigerator: same deal. Here's the process:
1) The compressor squashes the refrigerant into a liquid to squeeze its heat into a smaller space. It now feels very hot.
2) The hot liquid refrigerant is pushed into lots of small coils with fins, and a fan blows air over the coils. Most of the heat that is hotter than room temperature gets blown away.
3) Room temperature liquid refrigerant goes inside the fridge and is expanded in the evaporator coils. It expands, boils, and in boiling absorbs a lot of heat from inside the fridge. Its temperature plummets in the coils as it boils and expands, becoming much colder than the inside of the fridge; a fan inside the fridge blows not-cool-enough air over the coils, and the air's heat goes into the boiling liquid.
4) Expanded, cool refrigerant continues through the refrigerant line back to the compressor, to be squashed back into a hot liquid and have its heat carried away.
There are lots of materials that can work as refrigerants, including propane, helium, Freon, water and air. They all have their advantages and pitfalls.
The compressor gets hot because of the motor and it's in the middle of the refrigerant cycle, right there in the middle of the hot part of the refrigerant cycle.