The earliest known commercial air conditioning unit was developed in 1902 by W.H. Carrier for the Sacket-Wilhelms Lithographing and Publishing Company in Brooklyn, NY. Humidity was ruining the paper stock and Carrier was called upon to solve the problem. His simple and effective design blew the buildings’ warm moist air over chilled pipes. By cooling the air, the humidity was also reduced as cool air cannot hold as much moisture as warm.
Fast forward more than 100 years and today’s AC units still work on the same principal: warm air from a building is passed over refrigerant-filled coils, where it cools before being returned to the building, colder and dryer.
Here’s what happens: Inside your house is an air handler (sometimes in the basement, sometimes in the attic, sometimes part of your furnace). Within this air handler there is an evaporator coil holding liquid refrigerant. It looks very similar to the radiator in your car. Liquid refrigerant is designed to absorb heat from the surrounding air. Warm air from your house is pulled into the air handler. It passes over the evaporator coil. Inside the coil the refrigerant liquid absorbs the heat from the air and is converted into a gas. The gas is then pumped from the air handler to a condenser, usually outside. As it enters the condenser it is passed through a compressor. Now, under high pressure, the gas releases its heat which is blown out into the outside world by a fan. Then the now-cooling gas enters a condenser coil, is re-converted to liquid and pumped back to the air-handler. And on it goes, around and around.
The main parts of the AC system are:
the air handler/evaporator—holds the liquid refrigerant in the evaporator coil; receives warm air from the house and releases cool air back into the house
pump—moves the refrigerant gas from the air handler to the condenser
compressor—pressurizes the refrigerant gas and causes it to release heat
condenser—holds the cooling gas as it re-converts to liquid
expansion valve—regulates the flow of liquid refrigerant from the compressor back into the evaporator
pump—moves the liquid gas from the condenser to the air handler
Whether you have a central-air system or a small window-mounted unit the method is the same and, while things have undoubtedly become more technical over the decades, Mr. Carrier would surely recognize today’s air conditioners as a continuation of his own device.