Experimental Study for Heat Transfer Enhancement Due To Surface Roughness at Laminar Flow

An investigation was conducted to determine whether dimples on a heat sink fin can increase heat transfer for laminar airflows. This was accomplished by performing experimental studies using two different types of dimples: 1) circular (spherical) dimples, and 2) oval (elliptical) dimples. Dimples were placed on both sides of a aluminium plate with a relative pitch of S/D=1.21 and relative depth of δ/D=0.16 (e.g., circular dimples). 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, pressure drop, thermal performance and Nusselt number ratio were determined experimentally. For circular and oval dimples, heat transfer enhancements (relative to a flat plate) were observed for Reynolds number range from 600 to 2000 (Reynolds number based on channel height). Also the results are validated analytically for Nusselt number and friction factor for plain vertical plate. This experiment was undertaken to provide the needed experimental data that fill the gap for the use of dimples for laminar flow conditions. Specifically, this investigation was conducted to determine whether or not the use of dimples can enhance heat transfer characteristics for heat sink applications. Dimples enhanced heat transfer from its surface for laminar air flows while the pressure drop was equivalent or smaller than that of the flat surface. These surfaces do indeed enhance thermal performance without the penalty associated with higher pressure drops. I