Understanding the impact of Flow Bypass on the overall pressure drop of air cooled heat sinks

In this effort, theoretical modeling was employed to understand the impact of bypass on the flow performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink and the bypass regions were applied and a generic parameter, referred as the Flow Bypass Factor, was identified from the theoretical solution that mathematically captures the effect of flow bypass on the pressure drop across the heat sink. From the results obtained, it was found that at least in the laminar regime, the impact of flow bypass on performance can be neglected for cases when the bypass thickness is typically less than 5% of the fin height, and is almost linear at high relative bypass gaps (i.e., usually for bypasses that are more than 10-15% of the fin height). It was also found that the pressure drop depen ds quadratically on the bypass gap.