Thermal wakes measurement in electronic modules in the presence of heat transfer enhancement devices

This paper reports the thermal wake measurements in electronic modules in t he presence of heat transfer enhancement devices. The enhancement devices c onsist of various sizes and shapes of ribs, secondary air flow injections t hrough cylinders and "film cooling-like" injection devices. The effects of such devices on the thermal wake and the pressure drop characteristics of a n array of rectangular modules at different values of Reynolds number in th e range 4.0 x 10(3)-1.6 x 10(4) have been investigated. Generally, it was f ound that using sizes and shapes of ribs as well as the presence of seconda ry air flow injection cylinders and film cooling-like injection hole device s tends to results in a significant attenuation in the thermal wake, in par ticular in the region downstream of the enhancement devices, depending on t he location of the active module in the array. A maximum attenuation in the thermal wake of 33%, 30% and 25% for the rectangular, triangular and cylin drical ribs occurs at the sixth row, respectively, when the active module i s located just upstream of the rib-enhancement devices. The film cooling-li ke enhancement devices tend to have higher attenuation in the thermal wake than the rib enhancement devices for the same location of the active module downstream of these devices, but with very much smaller pressure drop. (C) 1999 Elsevier Science Ltd. All rights reserved.