HVAC空调系统介绍资料.ppt

* An example of a system that does not use the chilled-water loop is one that uses a packaged rooftop air conditioner, shown in Figure 30. It combines several components of the airside loop with all the components of the refrigeration loop. Similar to the central air handler shown earlier, return air from the space is drawn into the unit and is mixed with outdoor air that enters through a separate damper. This mixed air passes through the filters, the cooling coil (which is also the evaporator), and the supply fan before it is discharged from the unit. Packaged inside this same piece of equipment are one or more compressors, an air-cooled condenser complete with propeller-type fans, and expansion devices. * An example of a system that does not use the chilled-water loop is one that uses a packaged rooftop air conditioner, shown in Figure 30. It combines several components of the airside loop with all the components of the refrigeration loop. Similar to the central air handler shown earlier, return air from the space is drawn into the unit and is mixed with outdoor air that enters through a separate damper. This mixed air passes through the filters, the cooling coil (which is also the evaporator), and the supply fan before it is discharged from the unit. Packaged inside this same piece of equipment are one or more compressors, an air-cooled condenser complete with propeller-type fans, and expansion devices. * Heat-Rejection Loop The fourth loop is the heat-rejection loop. In the refrigeration loop, the condenser transfers heat from the hot refrigerant to air, water, or some other fluid. In a water-cooled condenser, water flows through the tubes while the hot refrigerant vapor enters the shell space surrounding the tubes. Heat is transferred from the refrigerant to the water, warming the water. In Figure 31, water enters the condenser at 85oF (29.4oC), absorbs heat from the hot refrigerant, and leaves at 100oF (37.8oC). The water flowing through the condenser mus