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
depends quadratically on the bypass gap.