Even after searching it up I still don’t understand how it cools down air.
And what exactly does Freon do?
In: 9
Compressing a gas into a liquid (increasing pressure) means heat is released from the gas as the pressure increases and especially as it changes to liquid form.
Having a gas expand means it will absorb heat as it expands.
Put a substance in pipes with a compressor and an expansion valve in the circuit and you have yourself a basic refrigeration cycle.
An A/C unit is just that.
You have a pipe coil with aluminium fins that is at the outlet of an expansion valve called the evaporator. A fan blows air through the fins and as the gas expands, the heat from the air is absorbed leading which cools the air.
Outside, you have a similar heat exchanger, but there is also a compressor. The gas gets compressed and the heat absorbed from the inside air gets released to the outside air.
Run the cycle in reverse and you have a heat pump.
Freon is a trademark owned by Dupont. People call it Freon, but the technical term is refrigerant. The refrigerant is a mixture of chemicals that has been tuned to have properties that work for the temperatures and pressures encountered in a typical AC. When the refrigerant is past the expansion valve, it is in gas form or at least partial gas form and turns back to liquid after going thorugh the compressor.
Commercial systems may use higher pressures and use different refrigerants. You even have systems that use CO2 as the refrigerant. It requires pretty crazy pressures, as in thousands of psi, but it can make a pretty good refrigerant.
ETA: A refrigerator uses the same principle. It cools what’s inside and dumps the heat at the back into your home.
ETA2: AC was first invented to help a printing business prevent humidity in the summer from making paper warp and jam in the printing presses. AC due to its effect of cooling air also decreases humidity. There was also obviously demand to keep indoors cooler than outdoors, so using it for the purpose of cooling was only a matter of time.
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