4630 -- Performance Analysis of Axial Fans in Residential Heat Pump Systems

The design and performance of axial fan blades in unitary air-conditioning systems are investigated numerically. The effect of propeller diameter, number of blades, and blade pitch (angle of attack) on the airflow rate, static pressure rise, and static efficiency are examined by solving the full three-dimensional flow equations across the fan blade. The tested configurations included 18 in. (457 mm) to 24 in. (609 mm) propeller diameters, two- to four-blade propellers, and a pitch range of 25 to 35 degrees. It was found that the peak static efficiency was highest in the pitch range of 40 to 45 degrees. The static efficiency decreased with the increase in number of blades. The static efficiency was insensitive to the propeller diameter, resulting in a flat curve in the range of the tested diameters. The increase in propeller diameter had the most pronounced effect in increasing the airflow rate. The increase in blade pitch up to the optimum pitch angle delivered the maximum increase in the static pressure rise. The results show that the best performance of the propeller occurs at the maximum possible diameter, within the physical constraint of the unit, using the least number of blades at the optimum pitch range.

Units: Dual