毕业论文外文翻译-集中供热和制冷设备的选择_精品.docVIP

CENRTRAL COOLING AND HEATING The energy used to heat and cool many buildings often comes from a central location in the facility. The energy input may be combination of electricity , oil ,gas , coal ,solar ,geothermal ,etc. This energy is typically converted into hot or chilled water or steam that is distributed throughout the facility for heating and air conditioning(cooling) . Centralizing this function keeps the conversion equipment in one location and distributes the heating and cooling in a more readily usable form. Also ,a central cooling and heating plant provides higher diversity and generally operates more efficiently with lower central location and a potentially large distribution system. This lesson addresses the design alternatives that should be considered when centralizing the cooling and heating sources in a facility. The economics of these systems require extensive analysis. Boilers ,gas , steam ,and electric turbine-driven centrifugal refrigeration units; and absorption chillers may be installed in combination in one plant . In large buildings with core areas that require cooling and perimeter areas require heating , one of several heat reclaim systems may heat the perimeter to save energy . The choice of equipment for a central heating and cooling plant depends on the following : Required capacity and type of use Cost and types of energy available Location and space for the equipment room A stack for any exhaust gases and its environment impact\ Safety requirements for the mechanical room and surrounding areas Type of air distribution system Owning and operating costs Many electric utilities impose very high charges for peak power use or ,alternatively ,offer incentives for off-peak use . This policy has renewed interest in both water and ice thermal storage .The storage capacity installed for summer load leveling may also be available for use in the winter ,making heat reclaim a more viable option. With ice storage, the low-temperature i