Fans and blowers
A fan is a driven fluid machine that raises gas pressure and conveys gas using mechanical energy supplied to it. In Chinese usage the term covers ventilating fans, blowers and wind turbines.
Fans are widely used for ventilation, dust extraction and cooling in factories, mines, tunnels, cooling towers, vehicles, ships and buildings; for draught and induced draught in boilers and industrial furnaces; for cooling and ventilation in air-conditioning equipment and household appliances; for drying and conveying grain; and for wind-tunnel air supply and the inflation and propulsion of hovercraft.
The main structural parts of a fan are the impeller, casing, inlet, support frame, motor, pulley, coupling, silencer and transmission parts including bearings.
Wind-driven ventilators use the natural wind and the thermal convection caused by the temperature difference between indoors and outdoors to turn a turbine, so that centrifugal force and negative pressure expel stale warm air from the interior.
Because fans determine the distribution energy consumption of a system, they are a critical part of building energy efficiency. Testing by the national air-conditioning equipment quality inspection centre has shown that many fans have problems even at rated operating conditions, so fans need to be produced and manufactured strictly in accordance with product standards.
