Study of Laminar Forced Convection Heat Transfer for Dimpled Heat Sinks

Abstract

An investigation was conducted to determine whether dimpled surfaces could improve the heat transfer in a heat sink under laminar airflows. This was accomplished by performing experimental and numerical investigations using two different dimple geometries: 1) circular (spherical) and 2) oval (elliptical or trenched) dimples. Dimples with a relative pitch of S/D = 1.21 and relative depth of δ/D = 0.2 (e.g., circular dimples) were machined on both sides of copper plates, then placed into a channel with airflow impinging over the leading edge of the plate. For oval dimples, similar ratios with the same total depth and circular edge-to-edge distance as the circular dimples were used. For those configurations the average heat transfer coefficient and Nusselt number ratio were determined experimentally. Heat transfer enhancements up to a 6% relative to a flat plate were consistently observed for Reynolds number (based on channel height) in the range of 500 to 1650 on both circular and oval dimples. Additionally, pressure drop, thermal performance, and flow characteristic were simulated numerically. The heat transfer coefficients in our numerical experiment were close to those of the experimental investigation for Reynolds number up to 750. The pressure drop over the dimpled plates was either equivalent to or less than that of the flat plate with no dimples.