Thermofluid analysis of staggered and inline pin fin heat sinks

A numerical study is performed of relative thermal and hydrodynamic efficiency of staggered and inline pin fin heat sinks. Advantages of the staggered over the inline design from the standpoint of cooling efficiency (under the same flow conditions) are evident. However, the staggered design has greater airflow resistance, leading to less airflow through the heat sink and a decrease in thermal efficiency. In this study we analyzed two sample pin fin heat sinks using the commercial CFD software Coolit. The heat sinks were placed on the bottom wall of a rectangular duct with thermally insulated walls. A heat source was located at the base of the heat sink. The major parameters of the process were the inlet velocity and the extent of shrouding defined by the distance from the heat sink to the duct walls. Both were varied to account for a wide range of flow conditions. The maximum temperature rise and the pressure drop over the heat sink were monitored. The main conclusion of this study was that the inline design is thermally superior to the staggered design for all but the fully-shrouded heat sinks. Another finding is that in a given geometry the non-dimensional pressure drop over a heat sink is almost constant, which indicates small viscous drag. Finally, the three-dimensional flow patterns and temperature fields obtained in the course of computations give insight into the complex heat sink airflow and heat transfer phenomena and suggest design improvements.