How does a refrigerator work?


I gotta know how my ice cream stays cold

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A pump compresses a gas into a liquid. The gas/liquid gets hot and the back of your refrigerator has a coil that lets some of the heat off before the liquor goes inside the refrigerator. Inside, the liquid goes through a restriction that turns the high pressure liquid into a low pressure liquid. Due to pressure change, the liquid absorbs heat. There is another coil on the inside that let’s the low pressure liquid evaporate into a gas all while absorbing heat. Then it flows back to the compressor.

A refrigerator contains two long tubes, or coils thru which a substance (refrigerant) is circulated by means of a compressor pump. In one of them (the evaporator coil) the refrigerant is passed thru a small hole into a wider section of the tube. The rapid expansion causes the refrigerant to lose heat, much the way sweat evaporating off your body cools you down. The cold refrigerant is able to pick up heat energy from the inside of the refrigerator box and carry it away from your food. The warmed refrigerant is then circulated to another coil on the outside of the box (the condenser) where this heat is released into the room or outside air.

A refrigerator, an air conditioner and a dehumidifier all use essentially the same mechanism to move heat from one place to another.

Boiling liquid absorbs heat. That’s the base thing to remember. For water, you have to provide that heat from outside, because water boils above room temperature. But not all chemicals are like that.

So you find a chemical that boils at a much lower temperature, such as freon. To make it into a liquid, you have to compress it. So you compress the gas until it turns liquid and you stuff it into a closed loop (with some liquid and some gas in the loop, just vibing). In order to make it boil, you can either raise its temperature (not ideal for making things cold) or you can change its pressure, like the reverse of how you made it liquid to begin with.

Enter the compressor pump. This pump pushes the gas through a one way valve, causing higher pressure on one side, lower on the other. The lower pressure side starts to boil, absorbing heat in the process. That newly-evaporated gas goes around the closed loop and condenses on the other side, releasing its heat. By putting the evaporation process inside the fridge and the condensation outside, you now have a way to move heat away from your ice cream and into your kitchen.

Hope that helps.

There’s a scientific thing called the Carnot Cycle. Which is a name for a thermodynamic principle. If you compress something it gets hot. If you let the temperature go to equilibrium the pressurized stuff is now room temp. Then if you release the pressure, it gets cold. Then you let it go back to equilibrium room temp. Then repeat.

How this works in the fridge is you’ve got 4 parts. A compressor, a heat exchanger, a throttle, and another heat exchanger. All of these are connected by a series of tubes. And these tubes are filled with a substance that will stay liquid at high temps and low temps. Typically Freon.

The compressor compresses the Freon, making it hot, it also pumps the hot Freon to a heat exchanger on the back of the fridge where the Freon exchanges heat with the ambient air and cools to room temp (this is why the back of your fridge is hot) then the Freon goes into the fridge and then through a throttle. A throttle is a device that lowers pressure and increases speed in a moving liquid. The lower pressure causes the Freon to get cold. It’s then run through another heat exchanger inside the fridge where it absorbs all the heat in the fridge bringing it back to equilibrium. This is what causes the fridge to get cold. The Freon then goes out the back of the fridge and back into the compressor and the cycle repeats.

Typically there’s some other stuff attached, like a thermometer that tells the compressor to turn on and off at certain temperatures, and fans by the heat exchangers to get them to exchange heat more quickly. That stuff helps, definitely makes it work better, but they arent strictly necessary.

You know your AC on the windowsill? It’s called a heat pump.

When the fridge has the same thing, hidden in it. The cold part is on the in side and the hot part is on the out side (i.e., towards the house).

It basically takes heat from inside the fridge and put it outside in the house. The heat pump can work even if the house is already warmer than the fridge (just like you can use a heat pump to cool the house when it’s hot outside or warm it up when it’s cold).

The fridge is insulated so the inside remains cold more easily so the pump doesn’t need to be as powerful or work as much as the windowsill A/C.