制冷与空调专业英语第2版 林慧珠 主编 5-4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 20 All-Air Systems Lesson 20 Text 　　　All-air system provides complete sensible and latent cooling, preheating, and humidification capacity in the air supplied by the system. No additional cooling or humidification is required at the zone, except in the case of certain industrial systems. Heating may be accomplished by the some airstream, either in the central system or at a particular zone.1 Text: All-air systems are classified in two basic categories: Single-duct systems, which contain the main heating and cooling coils in a series flow air path; a common duct distribution system at a common air temperature feeds all terminal apparatus. Text: Dual-duct systems, which contain the main heating and cooling coils in parallel flow or series-parallel flow air paths with either a separate cold and warm air duct distribution system that blends the air at the terminal apparatus, or a separate supply air duct to each zone with the supply air blended to the required temperature at the main unit mixing dampers. Text: All-air systems may be adapted to many applications for comfort or process world. They are used in buildings that require individual control of multiple zones, such as office buildings; schools and universities; laboratories; hospitals; stores; hotels, etc. 2 All-air systems are also used virtually exclusively in special applications for close control of temperature and humidity, including clean rooms, computer rooms, hospital operating rooms, research and development facilities, as well as many industrial manufacturing facilities. Text: 　There are some advantages and disadvantages of All-Air System. 　 Advantages: 　　1．The central mechanical equipment room location for major equipment allows operation and maintenance to be performe