Auto air conditioning is an air conditioning system that is specifically designed to provide climate control for the interior of an automobile. Before the introduction of air conditioning in automobiles, the only standard method of cooling the interior was to open the windows. Auto air conditioning creates a much more comfortable environment for the passengers of a vehicle.
Auto air conditioning works in a similar fashion as other forms of air conditioning systems. Heat naturally wants to move from a higher concentration to a lower concentration until there is a state of equilibrium. This is a principle known as heat transfer. Contrary to popular belief, an air conditioner does not actually work by cooling air, but rather by removing heat and humidity from the air.
Regardless of the specifics of a design, vehicle air conditioners are sealed, pressurized systems that generally consists of a compressor, condenser, and evaporator. A compressor is a pump that circulates the refrigerant through the air conditioning system. It also compresses or pressurizes the refrigerant; which heats it up, converting it to a vapor.
The refrigerant then travels to the condenser. It is here that the refrigerant is cooled down by a fan blowing on the condenser coils and converts to a liquid. As a colder liquid, the refrigerant is much more effective at removing heat than a vapor. Once converted to a liquid the refrigerant goes to the evaporator.
At the evaporator, a fan blows over the coils with the cold refrigerant in them. The fan forces the cooled air to enter the cabin of the vehicle. As this occurs, the refrigerant heat from the interior is transferred to the refrigerant. This in turn raises the temperature of the refrigerant, which converts it back to a gas state. From the evaporator, the now-liquid refrigerant is cycled back to the compressor where the process begins again.
Auto air conditioning was first introduced in 1939. The Packard Motor Car Company offered air conditioning as a $274 US Dollar (USD) option on the 1939 Packard. The Packard air conditioner was a rather rudimentary system that did not feature a thermostat or an independent shut-off feature. To turn off the air conditioning system, the engine needed to be turned off and the driver needed to disconnect the belt from the compressor.
By 1969, it was estimated that almost fifty percent of cars were equipped with air conditioning. By the late 1970s and early 1980s, auto air conditioning became even more common and it is estimated that approximately 80% of the automobiles now sold in the United States feature air conditioning.