How Air Conditioning Work

Sunday, February 22, 2009

AIR CONDITIONING FOR LARGE MULTISTOREY BUILDINGS

AIR CONDITIONING FOR LARGE MULTISTOREY BUILDINGS


DESIGN CONSIDERATION

Most large multistorey buildings are highly centralized air conditioning equipment. The roof and basement are the usual choice for these central station systems. The basement has the advantages of easy utility connections, noise isolation, not being valuable rental area and the fact that structural loads are not a problem. The roof on the other hand, is the ideal location for fresh air intakes and heat rejection to the atmosphere.

TYPES OF AIR CONDITIONING SYSTEMS

Large buildings have so many thermal zones, and there are so many ways to move heat from one place to another, that hundreds of air conditioning systems have been devised. One way to classify air conditioning systems is by the media used to transfer heat. Although thousands of liquids and gases can be used as carrier of heat, the three most common in building applications are air, water and refrigerant. Air conditioning for large buildings have three main system classifications:

a. All-air systems
b. Air and water systems
c. All water systems


ALL-AIR SYSTEMS

The great advantage of all-air systems is that complete control over air quality is possible. The main disadvantage is that all-air systems are very bulky and a significant part of the building volume must be devoted to them. It must be noted that for clarity only the supply ducts are shown on each plan in the following examples. Usually there is also a sizable return duct system on each floor.


AIR-WATER SYSTEMS

The following systems supply both air and water to each zone of a building. Although this increases the complexity of the mechanical systems, it greatly decreases the size of the equipment because of the immense heat-carrying capacity of water as opposed to air. Air is supplied mainly because of the need for ventilation.


AIL-WATER SYSTEMS

Since these systems supply no air, they are appropriate where a large amount of ventilation is either not necessary or where it can be achieved locally by other means such as opening windows.

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