ABSTRACT
Centrifugal fans are installed as part of packaged ventilation and air-conditioning equipment such as room air-conditioners, heating and cooling fan-coil units, prefabricated air-handling units, and outdoor dry and evaporative heat exchangers. Where a high pressure and air-flow duty is needed in extensive ducted systems, the centrifugal fan is usually free-standing installed within a plant room. In large air-flow applications the fan plant room also serves as a path for the air flow. In this case, the fan plant room becomes a plenum chamber that is maintained at a different static pressure than that of the atmosphere. A fan plenum chamber may be constructed from concrete and brickwork as part of the building structure. The building materials that are used, the quality of the surface finishes and the air tightness of the plenum are carefully controlled to ensure reliable long-term performance and low mainten-
Fig. 9.1 Types of fan blade.
