Effect of heat sink inlet and outlet flow direction on heat transfer performance

To improve performance of small electronic devices, it requires enhancement of heat transfer performance of liquid cooling and heat sink. Heat sink performance is known to be affected by a number of factors including: fin shapes, fin dimensions, fin gap space, number of fins, fin array arrangements, position of heat surfaces and type of cooling liquid used in heat sink. This study focuses on the simulation of cooling liquid flow through micro pin fins in heat sink using a commercial Computational Fluid Dynamics (CFD) program. The effects of flow direction at the heat sink inlet and outlet on the pressure drop and thermal performance were investigated. In this study, fins array in staggered arrangement with the porosity of 0.67 was made 6061 aluminum tube of 0.66 mm. diameter. The angle between inlet and outlet to heat sink side surface was then varied from 0 to 90 degrees for each type of heat sink (V-type vs. I-type) with pressure drop set to less than 3000 Pa. Correlation between pressure drop and thermal performance at various operating conditions was also analyzed. Based on the results obtained, the heat sink with the best heat transfer performance in this study was the V-type at 75 degree angle with a 2.5 mm. distance between heat sink front surface and inlet/outlet centerline. This type gave the highest heat transfer performance which presumably was attributable to the uniformly low temperature distribution at the heat sink base that consequently resulted from the effect caused by the angle or position of heat surfaces inducing the formation of large vortices at the heat sink inlet.