An air cooling system takes heat energy from the space to be cooled and drives it elsewhere in the building or outside. There are several types of systems, but most involve a fan driving hot air through ductwork. The heat energy can be released in the space being cooled or driven elsewhere such as into a suspended ceiling.
Air cooling systems are simple and relatively inexpensive. They can be used in a wide range of applications including refrigeration, air conditioning, industrial and domestic cooling. However, they have a number of weaknesses including their lack of control over the air temperature and their inability to handle humid conditions.
The primary method of air cooling is the use of a large surface area to maximize the amount of heat that can be transferred to the surrounding atmosphere. This technique has been in use for thousands of years and is a very effective method of cooling. In modern gas turbines, this type of cooling is primarily achieved by a serpentine passage from the hub to the blade or vane.
A similar technique can be applied to water-cooled equipment. The metal surfaces that contact the coolant are coated with thermal paste and the entire assembly is packed with a liquid coolant. As the coolant moves through the waterblock it absorbs the heat and moves upward to a radiator where fans are used to move the coolant away from the load to be cooled by the air. The coolant then reenters the waterblock and the cycle begins again.
In cars, motorcycles, aircraft and some stationary installations the air cooling principle is still used. An engine has cooling fins that extend outward and are forced by a fan in automobiles and by the vehicle or aircraft’s speed in other systems to pull cool air across them. This cooling is inefficient because it relies on a constant flow of cool air, which is not always available.
Liquid cooling offers more efficient and precise control over the cooling process and requires a less complicated installation. Liquid cooling is also more flexible in terms of operating conditions because the refrigerant can be pumped through a series of coils to provide different cooling configurations. Liquid cooling systems also offer a more compact design and have better performance than most air cooled systems.
The major disadvantage of a liquid cooling system is its cost and the need for regular maintenance to ensure that the piping does not develop leaks. In addition, the system needs a free-clear air supply that is not affected by prevailing winds or nearby buildings that could cause the heated refrigerant to be drawn back into the tower. This type of system is also susceptible to poor distribution of the refrigerant over the evaporator coil which can reduce its effectiveness. This is particularly true of microchannel evaporators which have many parallel channels fed from the same header. A closed loop evaporative cooling system uses the same concept but has a separate tower water cooler for the closed cooling loop that is not connected to the coolant piping and is therefore not affected by this problem.