Chilled water systems were used in less than 4% of commercial buildings in the U.S. in 1995. However, because chillers are usually installed in larger buildings, chillers cooled over 28% of the U.S. commercial building floor space that same year (DOE, 1998). Five types of chillers are commonly applied to commercial buildings: reciprocating, screw, scroll, centrifugal, and absorption. The first four utilize the vapor compression cycle to produce chilled water. They differ primarily in the type of compressor used. Absorption chillers utilize thermal energy (typically steam or combustion source) in an absorption cycle with either an ammonia-water or water-lithium bromide solution to produce chilled water.
Overall System
Figure 4.2.2 shows a simple representation of a dual chiller application with all the major auxiliary equipment. An estimated 86% of chillers are applied in multiple chiller arrangements like that shown in the figure (Bitondo and Tozzi, 1999). In chilled water systems, return water from the building is circulated through each chiller evaporator where it is cooled to an acceptable temperature (typically 4 to 7°C) (39 to 45°F). The chilled water is then distributed to water-to-air heat exchangers spread throughout the facility. In these heat exchangers, air is cooled and dehumidified by the cold water. During the process, the chilled water increases in temperature and must be returned to the chiller(s).
冷水機(jī)組
1995年，在美國(guó)，冷水機(jī)組應(yīng)用在至少4％的商用建筑中。而且，由于制冷機(jī)組通常安裝在較大的建筑中，在同一年里，制冷機(jī)組冷卻了多于28％的商用建筑的地板空間（DOE，1998）。在商用建筑中普遍采用五種型式的制冷機(jī)：往復(fù)式、螺桿式、旋渦式、離心式和吸收式。前四種利用蒸汽壓縮式循環(huán)來(lái)制得冷凍水。它們的不同主要在于使用的壓縮機(jī)種類的不同。吸收式制冷機(jī)在吸收循環(huán)中利用熱能（典型