US Patent 11603856 Backward curved plenum fan having enhanced efficiency

A centrifugal fan for use as a blower in a heating, ventilation, air conditioning, and refrigeration (HVACR) system has a plurality of blades each having a leading edge camber angle of at or about 10 degrees to at or about 30 degrees, a trailing edge camber angle of at or about 10 degrees to at or about 30 degrees, a stagger angle of at or about 35 degrees to at or about 55 degrees, and a chord having a length L, wherein the length L over the diameter of the centrifugal fan divided by the diameter D satisfies the inequality 0.25≤L/D≤0.42. The fan blades having these parameters provide improved fan efficiency at certain operating conditions. The fan blades may further have a forward or radial sweep. The fan blades may have a uniform thickness from the leading edge to the trailing edge.