How does an air conditioner cool down a room?
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The concept you need to grasp, is that for matter to change state, it either absorbs or releases energy.
As I’m sure you know, adding heat to water will turn it from a liquid to a gas, but water doesn’t have to be boiling to change state. If you have ever felt cold while getting out-of the shower, what you are experiencing is the water evaporating off your skin, and to do so, it is taking the heat from your body to make the phase change.
So an a/c unit utilizes this theory, that a liquid changing state to a gas requires energy. Using a gas that has a low boiling/condensation temp, it is easy to force the gas into a liquid state with a compressor, much like an air compressor. The action of squeezing the gas isn’t enough to liquefy it, so it is send to a condensing coil (the one outside with a big fan) to cool off and turn back into a liquid at high pressure. It’s the pressure that keeps it in liquid form, like propane in your BBQ tank.
Then it travels to the evaporating coil, and a special valve admits specific amounts of liquid into this coil, which is at a lower pressure(the one in your house) the liquid turns back into a gas and while doing so, pulls the heat out of its surroundings causes a cooling effect we can take advantage of by passing air over this coil.
The now gas travels back to the compressor to repet the cycle.
This can be done with water, but it’s a much different set up. They use a unit that is under a deep vacuum, and this low pressure allows for the water to change state at very low Temps.
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