Seriously, what is going on?
In: 1
It’s a heat pump!
Long story short. The walls of the fridge are constantly “stealing” warmth from inside and expelling that heat outside the fridge.
It does this using a fluid that can be compressed then turned to a gas and compressed repeatedly. This constant change of state is how the fridge moves the heat around.
More info from [Technology Connections] (https://youtu.be/7J52mDjZzto)
the temperature of a gas and the density of it are tied together.
this is the same for air/conditioners, dehumidifiers and heat pumps in the vast majority of situations.
so if you compress a gas it practically squeezes the heat out.
if you allow a gas to expand or force it it will absorb heat.
on the cool side there is an ‘evaporation or expansion radiator’ that radiator just encourages the transfer of heat energy from the air to the expanding gas housed inside(called refrigerant) that draws the heat out, or cools the air going over the radiator. that air is circulated inside the fridge.
on the other end is the compressor and compression radiator, the gas is pumped into a smaller space to squeeze the heat out. and the air(outside the fridge or house) gets warmer.
heat pumps are simply air conditioners designed to work both ways, typically just with a couple valves.
all gases do this, but some do it better than others.
Fridges have pumps that capture heat inside the box and releases heat outside the box.
How do they do this though?
To keep things simple, a special chemical flows through the fridge with a specific evaporation/condensation point. When the chemical changes states to a fluid it absorbs energy/heat and when that fluid turns back into a gas it disperses it. The chemical condenses to a fluid inside the fridge thus collecting energy/heat in the process, and turns back into a gas outside the fridge letting that heat back into the atmosphere.
Ever notice when you use a spray can that it gets cold?
That’s because gas gets cold when it expands. It’s a basic law of physics.
You’ll run into a big, obvious problem if you use a factory filled spray can to make stuff cold: The can will eventually run out.
So to build a fridge, you need to seal the system so the gas doesn’t escape, then after it’s sprayed you pipe it to a motor-driven fan to be re-compressed. Easy peasy.
Small problem, the basic law of physics works in reverse too: When the motor compresses the gas, it heats up equal [1] and opposite. This is easy to solve though, you just make a long squiggly pipe along the back of the fridge. By the time the hot gas gets all the way through the pipe, it’s back to room temperature.
This is why you can’t open the door to the fridge to cool the room: The heat coming off the back is equal [1] and opposite the cold coming from inside. In fact, that’s another basic law of physics: You can create heat, but you can’t destroy it; you can only move it around.
[1] Actually a little more than equal, because friction in the motor will add a little bit of heat.
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