How air conditioners take hot and humid air, and make it drier and cold.
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Air conditioners rely on some basic ideal gas laws that you probably learned in middle school. Let’s do a quick refresher.
* If you compress a gas, its temperature will go up.
* If you allow a gas to expand, its temperature will go down.
Here’s how your air conditioner uses these two laws to cool your house.
Outside your house, there is something called a compressor. This compressor pumps a gas into a copper tube that runs in a coil shape. At the other end of the long, coiled up tube is a tiny opening so that the gas cannot flow through quickly. The pumping action compresses the gas in the tube as it is blocked by the tiny opening, called the orifice.
As the gas is compressed, it gets hot. Like, really hot. Hot enough to burn your hand, and much hotter than the air is outside. Let’s say it gets up to 190°F, but the air outside is only 85°F. The compressor also has a fan that blows across the coils. The 85°F air blowing across the hot coils carries some of the heat away.
Inside your house is something called the air handler. It contains a fan that moves air around your house, and another, larger (diameter) coil of copper tubing that is connected to the compressor outside so that the two form a loop. Importantly, the orifice is also right at the beginning of the evaporator.
As the gas exits the orifice, it enters the larger diameter evaporator coil where it rapidly expands. Thanks to the ideal gas law we talked about earlier, this causes its temperature to drop rapidly. This causes the evaporator coil to get cold, because back when the gas was outside and very, very hot, we blew a fan across it to cool it down.
The fan in the air handler blows air from your home across the cold evaporator coil, cooling it. As the warm, humid air from inside your house hits the cold evaporator coil, condensation forms on the evaporator coil and drips into a condensation collection pan. The condensation pan has a pipe connected to it that carries the water away. Usually outside, but sometimes into a drain inside your house.
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