Ever wonder how that A/C in your cars keeps you nice and cool in the summer time. From the compressor to the pumps all the way to fan is explained in detail.

All air conditioning systems work in the same basic way, relying upon the principles of evaporation, condensation, compression and expansion, and consist of the same seven major components: the compressor, condenser, recover-drier, orifice tube or expansion valve, evaporator, hoses and of course refrigerant.

The refrigerant which is now HFC-134a (R-134a), boils at around-15.9F, which means it is typically a gas under standard atmospheric pressure. One of the basic principles upon which an A/C system operates is Latent Heat of Evaporation, which means that the refrigerant must be able to evaporate, so it must first become a liquid. If you're unfamiliar with the Latent Heat Principle, it's the same idea as how sweat helps regulate your body temperature on a hot day.

When you sweat, the moisture evaporates from your skin, absorbing heat in the process and creating a cooling sensation. With R-134a, to raise the boiling point high enough for the refrigerant to condense to a liquid at more realistic ambient temperatures, it must be highly pressurized.

The A/C system is a continuous loop that is split into a high pressure side and low-pressure side by the compressor. The high pressure created by the pumping of the compressor pushes the now heated and pressurized gaseous refrigerant through a hose into the condenser, where much of the heat causes the refrigerant to condense into a liquid state. The still-highly-pressurized liquid then flows into the recover-drier, which contains a filter to remove any debris within the system as well as desiccant material to remove any moisture or impurities from the refrigerant. (Moisture combined with refrigerant can form a corrosive acid)

The purified liquid refrigerant flows through the A/C hoses and into the cabin of the car, where it is then forced through a small orifice, either in the form of a fixed orifice tube or thermal expansion valve. the resulting fine mist that is metered by the valve (think of a finger over the end of a hose) blows into the evaporator located in the heater box under the dash. The drop in pressure caused by the expansion valve is sufficient to cause the refrigerant to vaporize as it moves into the evaporator, absorbing a good deal of heat in the process.

A fan located in the heater box blows ambient air across the now chilled evaporator, which absorbs heat from the air, and the resulting cooled air blows through the vents into the cabin. Because the cooled air has less capacity to hold moisture, the evaporator also dehumidifies the air.

Condensation develops on the evaporator and the water drips away through a drain in the evaporator box and causes the puddles usually seen under vehicles with the A/C running.

Depending upon the system design, as the gaseous refrigerant is sucked back toward the compressor, there may also be an accumulator attached to the outlet of the evaporator that serves to ensure no liquid refrigerant or moisture makes its way to the compressor.

And that's about it when it comes to learning how the A/C in your car works.

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