| Summary: | 碩士 === 中華大學 === 機械與航太工程研究所 === 91 === The present heat sink of most heat sink are rectangular shapes. Fins become parallel or irradiative arrays, extruded from the surface of substrate. The flow of forced convective fan is from the top surface coming, no flow blow out from hub of fan, results in stagnation region flow at center of heat sink , and lower the efficiency of heat transfer rate. In order to innovating from the traditional rectangular shapes, the ring shapes flow passage fins are designed. The geometry between fins and substrate becomes more streamline, and the flow becomes secondary flow and vortex structure. The higher heat transfer rate will be expected. This paper run the Star-CD code to help and audit design. Compare with sample measuring temperature. To understand the design weighting of heat conduction and heat convection. Major factor is flow resistance of supplied pressure and flow in heat sink , and flow over a fin surface near heat source. The faster flow near heat source the more efficiency of heat transfer rate.
The more heat conductive volume the less heat convective surface under same volume of heat sink. In this study, the cross section of the flow channel ratio between ring-type and rectangular-type is 8.5 : 21.5 cm2 . Relative pressure drop ratio is 42.3 : 29.2 Pa and flow pass through the channel is 0.151 : 0.472 m3/min after run Star-CD. The average velocity ratio is 2.97 :3.77 m/s . Finally, compare with temperature at the center of heat source is 68.0 : 53.5℃. Consequent, Under forced convective cooling, heat convection is dominant with aluminium alloy material.
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