How a refrigerator moves heat
Your fridge does not make cold. It moves heat. The vapour compression cycle as a loop you can follow with your eye.
The problem,
and the picture.
The brief
Thermodynamics students meet the refrigeration cycle as a T-s diagram. The physical loop behind it rarely gets drawn.
The approach
A cutaway fridge with the refrigerant loop drawn around it: compressor, condenser coils on the back, expansion valve, evaporator. Liquid and vapour are marked in two colours, and each part labels itself as the narration reaches it.
- FieldEngineering
- Runtime1:02
- Made forStudio sample
- SourcePurdue University ME 200 Thermodynamics notes
The narration.
Your fridge doesn't make cold. It moves heat, from inside the box to the room outside. Here's how. A fluid called the refrigerant flows round a closed loop through four parts. First, the compressor squeezes the refrigerant vapour. Its pressure and temperature shoot up, until it's hotter than the room. So in the condenser, the coils on the back, heat flows out into the room, and the vapour condenses into a liquid. Next, the expansion valve. The liquid is forced through a narrow opening. Its pressure drops, and it turns cold, colder than the inside of the fridge. Finally, the evaporator. Heat from your food flows into the cold refrigerant, which boils back into vapour and returns to the compressor. Squeeze, release heat, expand, absorb heat. Round and round. That's the refrigeration cycle.