Eli5: How do refrigerators work?
In: Technology
Usually heat only wants to flow from a higher-temperature area to a lower-temperature area.
But something neat happens to gases when they compress and expand. Compressing a gas makes its temperature rise. Letting a gas expand makes its temperature lower.
So if you compress a gas, it will get hot. But what if you then take that hot, compressed gas, and let it cool down? Well, then , you have some cool, compressed gas. Now, if you let the gas expand again, it will get cold! Much colder than it was when you started.
So the trick is, you compress the gas over here outside the to make it hot, and then let it radiate all that heat away through the grille on the back of the fridge. Then you bring that compressed gas back over there to the inside the fridge, and then let it expand, and it gets very cold, and the cold gas is warmed up when heat flows into it from, say, your vegetables.
The fridge achieves all this by pumping the gas, called a refrigerant, through a closed circuit of pipes. (It’s actually not always in the gas phase; usually it condenses into a liquid for part of the cycle, but that’s not really important to the basic principle here. Refrigerants are generally fluids which boil and condense at just the right temperatures and pressures to make this process most efficient.)
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