How Air Conditioners and Heat Exchangers Work

Air Conditioners

• The air conditioning process is familiar to many, with window units and central air systems a ubiquitous presence in many homes and businesses around the world. Through the use of a refrigerant liquid, hot air is taken out of a room, cooled, dehumidified then injected back into the room. Besides the refrigerant, the main parts of an air conditioner are the compressor, condenser and evaporator, which all work together to cycle and transform the refrigerant.

Cooling Process

• The ability of refrigerant, known as freon, to change from a liquid to gaseous state and back again is at the heart of the air conditioning process. A compressor circulates refrigerant in a closed loop between an evaporator and a condenser, taking advantage of the natural cooling property of the refrigerant to withdraw heated air from inside a room and pass it over coils, also filled with freon, thereby cooling the air in the process. Some of the hot air is sent outside while the rest, now cool and comfortable, is vented back into the room.

Heat Exchangers

• Though heat exchangers are frequently found in industrial settings, the human lungs are a good example of the principle involved in action. The core idea is to transfer heat from one liquid or gas to another without allowing the two to mingle. Generally, the goal is to cool one of the substances down from a superheated state, after use, in some sort of manufacturing or industrial process. With a heat exchanger, the key is movement and surface area.

Heat Diffusion

• A heat exchanger is typically a unit with two chambers separated by a wall. The more common surface area the two chambers share, the more effective the exchanger will be at cooling down the hot liquid. A common design is to have two pipes side-by-side, snaking back-and-forth. A liquid, sometimes water, is pumped into one chamber. Since refrigerant is not used for cooling, the liquid assumes room temperature, which is much cooler than the hot liquid in the other chamber. Heat diffuses between the two until a common temperature is reached.