How air conditioners take hot and humid air, and make it drier and cold.
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It’s basically magic. Google the “vapor-compression refrigeration cycle”.
The ELI5 version is that your refrigerator (or water cooler or AC unit) takes heat from a cold source and rejects it to a hot source. Normally, heat wants to flow from a hot source to a cold source. That’s the magic part. Your refrigerator does this by putting the refrigerant into a state where it really wants to boil (evaporate) at the right temperature – usually around 40-45 degrees F. When it evaporates, it sucks heat out of its environment….which can be the air in your refrigerator, or the air in your room, or the drinking water in a water cooler. In doing so, it cools the air or water.
The more complicated / complete version is that there’s four stages in the vapor-compression refrigeration cycle….which acts on a refrigerant. (Refrigerants are just chemicals that are typically gas at normal conditions, but which can be put into liquid states where they really “want” to boil or evaporate.)
So the four stages of the cycle are compression, condensation, expansion, and evaporation…..which occurs on the refrigerant.
The compression is done by….the compressor. The refrigerant is a gas at this point, and is compressed to a higher temperature and pressure. That’s the part of your refrigerator (or water cooler or window AC unit) that makes that kind of low rattling / humming noise. If you put your hand on it, it will be hot.
The condensation is done by….the condenser. At this point, the refrigerant starts as a hot gas and condenses into a hot liquid, still at high pressure. This corresponds to the heat being rejected from your refrigerator. The condenser coil is the part of your refrigerator that blows hot air into your kitchen.
The expansion is done by…the expansion valve. The refrigerant passes through the valve, and expands to a lower pressure. You don’t see this.
The final stage, where the actual cooling occurs, is evaporation. The refrigerant is in a state where it’s just dying to boil, and changes phase from a liquid into a gas. Whenever anything boils (evaporates), it sucks heat out of its environment. This occurs in the evaporator – which can be an air coil, or a water heat exchanger. In your refrigerator, this happens in the little blower coil that’s inside the refrigerator, near the top of your refrigerator. In a water cooler, it’s a copper heat exchanger that has refrigerant in one side and drinking water in the other side.
The important point of all this is that these three stages (compression, condensation, expansion) are all there to just get the refrigerant into a state where it really “wants” to evaporate….and suck heat out of its environment….thus causing a cooling effect.
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