This experimental study investigates the heat transfers in three side-opened and bottom-sealed rectangular channels with two opposite walls roughened by 90° staggered ribs, which simulate the enhanced cooling passages in the fin-type heat sinks of electronic chipsets. The various degrees of interactive effects due to the surface ribs, side-profile leakage flows and streamwise weakened coolant flow are functionally related with Reynolds number (Re) and channel length-to-gap ratio (L/B), which unravel the considerable impacts on local and spatially averaged heat transfers over the rib-roughened fin surfaces. A selection of detailed heat transfer measurements over the rib-roughened fin surfaces illustrates the manner by which the isolated and interactive influences of Re and L/B-ratio affect the local and spatially averaged heat transfers. Relative to the heat transfer results acquired from the smooth-walled test channels, the augmentations of spatially averaged heat transfers generated by the present surface ribs are in the range of 140–200% of the flat fin reference levels. In conformity with the experimentally revealed heat transfer physics, a regression-type analysis is performed to develop the correlation of spatially-averaged Nusselt number over rib-roughened fin surface, which permits the individual and interactive effect of Re and L/B on heat transfer to be evaluated. A criterion for selecting the optimal length-to-gap ratio of a fin channel, which provides the maximum convective heat flux from the rib-roughened fin surface, is formulated as an engineering tool to assist the design activity for the cooling device of electronic chipsets.
Relation:
International Journal of Thermal Sciences, Vol.43 no.2, pp.85-200
