Experimental modeling of convection upstream from a row of electronic packages

Experiments on convective heat transfer immediately upstream of a row of closely spaced electronic packages are reported. Flow visualization and interferometric heat transfer measurements were made in an induced draft wind tunnel where the package row is modeled with a two-dimensional transverse rib attached to one channel wall. The transverse rib has an aspect ratio of 4.3, and the channel-height-to-rib-height ratio was varied between 1.2 and 4.0. Results are reported for Reynolds numbers ranging from 2000 to 5000. Flow visualization shows that the approach flow separates from the channel wall approximately one rib height upstream from the rib. Under most conditions the region of separated flow consists of a single cell; under some circumstances a quasi-steady double-cell structure is observed. The region of reduced heat transfer extends approximately 2.5 rib heights upstream, with the heat transfer coefficient dropping to very small values near the recirculating cell. The average heat transfer upstream from the rib is reduced to approximately 50% of that which would occur in the absence of the rib. It is found that if as little as 10% of the approach flow is removed from the base region at the front of the rib, the heat transfer coefficient is restored to values which would occur in the absence of the rib