On the Fast Prediction of the Aerodynamic Performance of Electronics Cooling Fans Considering the Effect of Tip Clearance

This study aims to complete and validate a recently developed reduced-order model for the fast prediction of aerodynamic performance ( $P - Q$ ) curve of electronics cooling fans, taking into account the real fan geometry and the tip clearance effect. The effect of tip clearance on tip vortex generation and fan performance was revealed by an experimentally validated 3-D computational fluid dynamics (CFD) method. Six different tip clearance ratios ranging from 0% to 12.7% were investigated. The tip clearance was found to have a strong effect on tip vortex generation, which significantly affects the aerodynamic performance of the fan. Fan efficiency increased by up to 7% by reducing the tip clearance ratio by 2.5%. The tip clearance effect was successfully included by the analytical method combined with a correlation equation developed based on the CFD study. The results show that the combined reduced-order model can produce reasonably accurate predictions for fan $P - Q$ curve with errors less than 7.1% compared with CFD results, while having a wide valid range of tip clearance ratio up to 10%. The precision of this model was further validated against experimental results for eight commercial fans. The computational speed of this model is more than three orders of magnitude faster than a steady-state CFD study, making it highly appropriate for fast analysis of fan performance and thermal-flow codesign.