A car’s AC works much in the same way a residential air conditioning system works, but on a much smaller scale. The first and most important element is refrigerant. In the case of most vehicles built after the 1990s, the refrigerant of choice is R134a. It’s less damaging to the environment, the ozone layer in particular, than its pre-1990s predecessor, R12 (also known by the brand-name Freon).
A car’s AC depends on the thermodynamic properties associated with these operating within a closed loop under the correct pressure.
1. The thermodynamic properties of refrigerant gases under pressurization are a complex process, but in a nutshell, when refrigerant in its cool liquid form is exposed to warm air, it evaporates into a gas and absorbs or removes heat from the surrounding environment. This occurs in an AC component in the car known as the evaporator. It’s important to note here that an AC system doesn’t technically produce cool air, it removes heat from the air via the evaporator, then relies on the car’s blower and air ducts to blow cool air out into the cabin.
2. Now that the refrigerant has removed heat from the cabin, the hot refrigerant in gas form then travels to a separate part of the system, where the gas is compressed by the compressor.
3. Already heated by absorbing heat through the evaporator, the compression process creates even more heat. To remove this heat and once again cycle cool liquid through the system, the hot refrigerant gas is forced through a series of coils in the condenser, which is similar to a radiator in that it dissipates heat. The pattern of the coils creates a wide surface area in a compact space. Blowing air across this surface (created by the vehicle’s movement or a fan), dissipates the heat, turning the refrigerant gas back into a cool liquid.
4. Before the refrigerant can cycle back through the system, any water that may have been created in the process needs to be removed. This is achieved by a component known as a receiver or dryer. Once the water is removed, the refrigerant can start the cycle all over again.