Here in Yuma air conditioning is more than a luxury, it is a must have for our homes, our businesses, our cars and all the places we visit each day. But, did you ever wonder just how air conditioning (a/c) works? How does it make the “cold” air that keeps us cool in all those places?

For starters, a/c systems do not create cold air at all. They simply remove heat from the air making it feel cold. What you feel as cold air is really air that has had heat removed from it. Never thought about it that way before did you? 

So, how does the a/c system remove heat from the air? Utilizing a gas that is known as a “refrigerant”, the system uses energy to run a compressor that compresses the refrigerant to pressures well over 200 PSI that cause the gas to become heated. Refrigerants are things with commonly known names such as ammonia and freon, as well as a class of many compounds known as chlorofluorocarbons due to their chemical make-up.

The compressed refrigerant becomes very hot during the compression process. The hot gas then runs from the compressor to a component known as a “condenser”. The condenser acts just like a car’s radiator, as the gas passes through the condenser, air flow removes heat from the gas as the compressed gas now turns to a liquid as heat is removed from it. Kind of the reverse of what happens to a pot of boiling water. As heat is added, the liquid turns to a vapor. Condensation works in the reverse, turning gas into liquid. That’s why when you walk past that noisy thing running in your back yard with the fan blowing you get blasted with hot air. That “hot” air is the heat being removed from the refrigerant. This removal of heat by the condenser is what keeps the interior of whatever cool.

The liquid refrigerant is then sent to a device that goes by many names but in cars it is most commonly known as an expansion valve. There, the liquid refrigerant is forced under pressure through a very small opening known as an orifice. The sudden expansion of the liquid now turns the refrigerant back into a gas as the sudden expansion and return to a gaseous state absorbs energy or, as we know it, heat. Back to the boiling pot of water, as the pot boils, it is taking in energy (heat) which turns the water into steam (gas).

The rapidly expanding gas passes through a coil and fin unit known as the evaporator. An evaporator is like a radiator in design except that it is taking in heat rather than giving it off. As air is pushed through the evaporator by the blower motor, heat is removed from the air due to the refrigerant taking in energy as it passes from a liquid to a gas, and it ends up coming out the vents as what we know as cold air (air with energy removed from it). The now gaseous refrigerant flows to the compressor and the cycle starts all over.

You may have noticed the very practical terms of the major components, they are all named for what they do. Not very clever names, but quite practical!

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Posted in Car Advice