Scale Effects in Cross-Flow Fans. Effects of Fan Dimensions on Performance Curves.

Abstract

Experimental investigations into an affinity law of cross-flow fans have been conducted using three fans of different sizes but good geometrical similarity, and anomalous scale effects appearing on the performance curves have been shown. The results obtained have been confirmed with a series of additional experiments which examine the effects of errors of geometrical configurations of tested fans, as well as effects of the flow turbulence and velocity distributions of the inlet flow into the fans. The critical Reynolds number based on the chord length and tip speed of the rotor is as small as (1.0∼1.5)×104. The performance curves represented in a conventional nondimensional form are affected by Reynolds number as well as the fan dimensions, which shows that the performances of cross-flow fans never simply obey the conventional affinity law of fans, hence it is essential to introduce the fan dimensions to represent the performance in a general form.