制冷与空调专业英语第2版 林慧珠 主编 5-2新.pptVIP

Unit Five Lesson 17 Evaporative Air Cooling Lesson 18 Room Air Conditioners Lesson 19 Methods of Food Freezing Lesson 20 All-Air Systems Lesson 18 Room Air Conditioners Lesson 18 Text A room air conditioner is an encased assembly designed as unit primarily for mounting in a window or through a wall. These units are designed for the delivery of cool or warm conditioned air to the room, either without ducts or with very short ducts up to a maximum of about 48 psi. Each unit includes a prime source of refrigeration, dehumidification, and means for circulating and cleaning air, and may also include means for ventilating and/or exhausting and heating. Text: 　　　　　　　　　　　　　The basic function of a room air conditioner is to provide comfort by cooling, dehumidifying, filtering or cleaning, and circulating the room air.1 It may also provide ventilation by introducing outdoor air into the room and/or exhausting room air to the outside. Also, comfort may be provided by controlling the room temperature through selection of the desired thermostat setting. The conditioner may provide heating by heat pump operation, electric resistance elements, or by a combination of both. 2 Text: Warm room air passes over the cooling coil and, in the process, gives up its sensible and latent heat. 3 The conditioned air is then recirculated in the room by a fan or blower. The heat from the warm room air vaporizes the cold (low-pressure) liquid refrigerant flowing through the evaporator. The vapor then carries the heat to the compressor, which compresses the vapor and increases it’s temperature to a value higher than the temperature of the outdoor air. 4 Text: In the condenser, the hot (high-pressure) refrigerant vapor liquefies and gives up the heat from the room air to the outdoor air. The high-pressure liquid refrigerant then passes through a restrictor, which reduces its pressure and temperature. The cold (low-pressure) l