Centrifugal Fan Performance Characteristics

A centrifugal fan is essentially a variable flow rate, constant pressure device. At a constant rotational speed, the theoretical pressure-flow rate curve of a centrifugal fan should be a straight line. However, due to internal losses, the actual characteristic curve is curved. The pressure generated in a centrifugal fan is significantly affected by changes in inlet air temperature or density. For a given inlet air volume, the pressure is lowest at the highest inlet air temperature (lowest air density). For a given pressure-flow rate characteristic curve, there is also a power-flow rate characteristic curve. When the blower operates at a constant speed, for a given flow rate, the required power increases as the inlet air temperature decreases.