An air cooling system works by blowing cool outdoor air across a refrigerant coil inside the indoor unit. The heat in the air is absorbed by the refrigerant, which becomes a gas.
This is the method used in most cars, motorcycles, aircraft and many small stationary installations. The quality of cooling air is regulated thermostatically.
Thermodynamics
Thermodynamics, literally meaning heat and power (dynamics), is the science that explains how thermal energy can be transferred from one object to another. Cooling systems rely on thermodynamics in order to remove the heat from your building and transfer it outside of that area.
The vapor-compression cycle that powers most air cooling systems works by using mechanical energy to move thermal energy from a low temperature to a high temperature. The system’s efficiency is calculated by measuring the ratio of the output (cooling) to the input (mechanical energy). This ratio is known as the coefficient of performance or COP.
The refrigerant, which is a chemical substance in some cooling systems, absorbs heat at the evaporator and rejects it at the condenser. A compressor, metering device, and expansion valve help manipulate the pressure of the refrigerant to make this cycle possible. The suction lines, which transport cold vapor back to the compressor, should be insulated to control condensation and limit parasitic heat losses.
Heat Exchangers
Air cooling systems use heat exchangers to cool gasses such as hydrogen, nitrogen and carbon monoxide. They also remove contaminants from the exhaust and prevent them from being circulated throughout the house or building. This helps to prevent carbon monoxide poisoning.
Air cooled heat exchangers (ACHEs) dissipate heat from process fluid by passing ambient air over a bundle of finned tubes. They are common in petrochemical and power generation applications where cooling water is scarce or costly, when recirculation of cooling tower plumes is not permitted, or when environmental regulations prohibit the discharge of waste streams into surface waters.
Fans mounted below (forced draft) or on top (induced draft) of the ACHE move the air over the tube bundle. They may be designed to be easily removed for inspection and maintenance. For operation in cold climates, a winterization system is often provided to pre-heat the ACHE bay before starting up. The system includes louvers and actuators and is powered by electric motors.
Fans
A series of fans cool various components within the case. More fans are needed when building custom, high-powered PCs and they take up more space than liquid cooling does.
Fans come in various shapes and sizes. The size is usually indicated by the mounting holes on the frame, with square 120 mm fans being used in more demanding applications and smaller 80 mm fans used where larger fans would not fit or are not compatible.
Fans with impedance protection, overheat protection and low speed alarms are available. The latter protect the motor from damage by keeping the temperature down when the fan is running and reducing heat generation. The former prevents the fan from locking if the ambient temperature rises suddenly or input current increases for some reason. This ensures that the fans are always operating at optimum performance. They can also detect when they are defective, which enables them to be replaced more quickly.
Filters
Air filters are an important component of an air cooling system. They remove harmful particles from the air as it circulates. Those particles could be dust, mold spores or smoke and fumes. Filters are rated according to their ability to trap pollutants by the industry standard known as MERV (Minimum Efficiency Reporting Value).
HEPA air filters are highly efficient in filtering both large and small pollutant particles. They are often used in clean rooms for IC fabrication, medical facilities and automobiles. They are also available for home use.
UV light air filters kill bacteria and viruses using short-wave ultraviolet radiation. These filters are generally more expensive and need replacement every few years.