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【正文】 ms are either reciprocating, screw, scroll, or centrifugal in design. A small number of centrifugal chillers are sold that use either an internal bustion engine or steam drive instead of an electric motor to drive the pressor. [1]節(jié)選自 James B. Bradford et al. “HVAC Equipment and Systems”.Handbook of Heating, Ventilation, and . Jan F. Raton, CRC Press LLC. 2020 浙 江 海 洋 學(xué) 院 畢 業(yè) 設(shè) 計 2 FIGURE A dual chiller application with major auxiliary systems (courtesy of Carrier Corporation). The type of chiller used in a building depends on the application. For large office buildings or in chiller plants serving multiple buildings, centrifugal pressors are often used. In applications under 1000 kW (280 tons) cooling capacities, reciprocating or screw chillers may be more appropriate. In smaller applications, below 100 kW (30 tons), reciprocating or scroll chillers are typically used. Vapor Compression Chillers Table shows the nominal capacity ranges for the four types of electrically driven vapor pression chillers. Each chiller derives its name from the type of pressor used in the chiller. The systems range in capacities from the smallest scroll (30 kW。英文翻譯 Chilled Water Systems[1] Chilled water systems were used in less than 4% of mercial buildings in the . in 1995. However, because chillers are usually installed in larger buildings, chillers cooled over 28% of the . mercial building floor space that same year (DOE, 1998). Five types of chillers are monly applied to mercial buildings: reciprocating, screw, scroll, centrifugal, and absorption. The first four utilize the vapor pression cycle to produce chilled water. They differ primarily in the type of pressor used. Absorption chillers utilize thermal energy (typically steam or bustion source) in an absorption cycle with either an ammoniawater or waterlithium bromide solution to produce chilled water. Overall System Figure 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 7176。C) (39 to 45176。 8 tons) to the largest centrifugal (18,000 kW。 whereas, reciprocating chillers have the worst efficiency of the four types. The efficiency numbers provided in the table are the steady state fullload efficiency determined in accordance to ASHRAE Standard 30 (ASHRAE, 1995). These efficiency numbers do not include the auxiliary equipment, such as pumps and cooling tower fans that can add from to kW/ton to the numbers shown (Smit et al., 1996). Chillers run at part load capacity most of the time. Only during the highest thermal loads 浙 江 海 洋 學(xué) 院 畢 業(yè) 設(shè) 計 3 in the building will a chiller operate near its rated capacity. As a consequence, it is important to know how the efficiency of the chiller varies with part load capacity. Figure shows a representative data for the efficiency (in kW/ton) as a function of percentage full load capacity for a reciprocating, screw, and scroll chiller plus a centrifugal chiller with inlet vane control and one with variable frequency drive (VFD) for the pressor. The reciprocating chiller increa
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