Analysis of the effect of bypass on the performance of heat sinks using flow network modeling (FNM)

Heat sinks are used in electronics cooling systems to provide extra area for transfer of the heat dissipated by semiconductor devices. However, in presence of clearance regions around the heat sink, flow that would otherwise go through the heat sink bypasses it. This study uses the technique of flow network modeling (FNM) to analyze the effect of flow bypass on the heat transfer performance of a plate fin heat sink. The physical situation analyzed corresponds to a typical wind tunnel test cell used for characterization of the heat sink performance. Results of network analysis predict that increasing the bypass region has a strong effect on decreasing the flow rate through the heat sink. Therefore, the effectiveness of the heat sink is reduced when large clearance regions are present around it. The network analysis is shown to be very easy, quick, and accurate. It can be used for analysis of the placement of heat sinks in practical cooling systems.