Enhanced heat transfer performance of cylindrical surface by piezoelectric fan under forced convection conditions

摘要

Many electronic components have a cylinder form. However when force convection is applied to a cylindrical tube, a low heat transfer performance occurs in the wake area behind the tube. Accordingly, in the present study, a piezoelectric fan is used to enhance the heat transfer performance. The flow fields around the fan tip and cylindrical surface are examined using a flow visualization technique. Furthermore, three-dimensional numerical simulations are performed to examine the detailed characteristics of the heat and fluid flow fields generated by the vibrating fan. The numerical and experimental results show that the vibrating fan blade produces a jet-like flow, which mixes the free stream and the fluid in the wake region and prompts an improved heat transfer performance as a result. It is shown that the vibrating fan enhances the overall heat transfer ratio as much as 132%, and the local heat transfer ratio up to 214%. However, given a large fan tip amplitude, a large fan tip-to-heated surface clearance distance and a Reynolds number greater than Re_D = 2200, the jet flow induced by the vibrating blade reduces the heat transfer from the cylindrical surface.