How Air Conditioning Works – AC’s work by removing the heat from the space they service. An AC is simply a big refrigerator that uses the process of refrigeration to provide cooling for a building. AC’s work by using direct expansion coils or chilled water coils to absorb and move the heat from the air as air is blown across the coils. Types of air conditioner systems that use direct expansion coils for cooling are window units, split system air conditioners, package unit air conditioners, packaged terminal air conditioners like the air conditioners used in hotels, and mini-split ductless AC’s.
How Air Conditioning Works - The Air Conditioner Components
Air conditioners which utilize chilled water for air conditioning are typically commercial air conditioners for large commercial buildings. It doesn’t matter what type of air conditioner is used, the coils in the air conditioner system are brought to a temperature colder than the air. These air conditioners coils are designed with materials like copper or aluminum to absorb heat easily and pass this heat to the refrigerant whether the refrigerant is Freon or another type refrigerant chemical or whether that refrigerant is water. Any type of refrigerant is designed to absorb heat. That is how air conditioning works.
AC’s use refrigerant that is pumped through coils where the refrigerant can either absorb heat or reject heat. For the process of how air conditioning works there needs to be some primary air conditioning components in the air conditioner system. The following is a description of the chief components in an air conditioning system that will show you how an air conditioner works.
The Air Conditioner Compressor
There are different types of compressors used in air conditioning. There are scroll compressors, reciprocating compressors, rotary compressors, screw compressors, and centrifugal compressors. All the different types of compressors have different capacities and are used in various applications. The AC compressor is like a pump. It pumps cool refrigerant vapor from the evaporator and compresses the vapor. When the refrigerant vapor is compressed its pressure and temperature are raised. This high temperature vapor is pumped to the AC condenser coils.
The condenser coils receive the hot vapor from the compressor and immediately the compressor begins to condense the refrigerant into a liquid by removing heat from the hot vapor. The heat being removed from the hot vapor is the heat the refrigerant absorbed when the refrigerant was running through the evaporator coils. The condenser is responsible for rejecting the heat absorbed in the evaporator coil.
The Metering Device
The most widely used metering devices are thermostatic expansion valves (TXV) followed by piton metering devices and capillary tubes. The refrigerant leaves the condenser as a liquid and is pumped to the metering device. The metering device meters the refrigerant only allowing a certain quantity to get past it. Typically the quantity of refrigerant is based on the size or capacity of the air conditioning system. TXV’s will meter the refrigerant based on superheat or a calculated quantity of refrigerant needed to satisfy demand. Capillary tubes and pistons meter the same quantity of refrigerant no matter the demand. This is the reason why TXV metering devices are used in air conditioner systems rated for higher efficiency than the AC systems that use capillary tubes or pistons to meter the refrigerant. The bottom for metering devices in an air conditioner system is that the metering creates a pressure drop of the liquid refrigerant. When the refrigerant drops in pressure it drops in temperature. Some of the liquid will flash to a gas state depending on the temperature pressure relationship but the refrigerant is now cold and ready to enter the evaporator coil.
The Evaporator Coil
The evaporator coil in an AC system is responsible for absorbing heat. As air (can also be water in a chiller) passes over the evaporator coils a heat exchange process takes place between the air and the refrigerant. The refrigerant absorbs the heat and as it absorbs heat is flashes to a vapor. The evaporator conditions the air in two ways when it is typically operating below the dew point. It causes sensible cooling and it causes latent heat removal. The latent heat removal is the process of drawing moisture out of the air and the sensible cooling is dropping the temperature of the air. Both types of heat removal make you more comfortable in the summer time. Most evaporator coils can be found in or near the air handling unit.
All the components mentioned in How Air Conditioners Work article are necessary components to make any AC system work except in evaporative coolers or swamp coolers which use a different process to create cooling. There are different types of components in the AC system but by an large air-conditioners need these basic components to work. In higher efficient models of AC’s more components are added especially controls to make the AC more efficient.
Air Conditioner Service and Repair - Another great article from High Performance HVAC to help you with air conditioner problems and diagnosis. Another article to help you learn about how air conditioners works - Air Conditioner Sequence of Operation.
Additional resources for How Air Conditioning Works and an in depth look – Refrigeration and Air Conditioning Technology
How Air Conditioning Works