Design and Analysis of a micro-scale Heat Exchanger

Abstract

The effect of passive fluid mixing upon convective heat transfer across rectangular micro-channels within the laminar flow regime has been numerically investigated. Proposed model makes use of a novel diverging-converging base corrugation design combined with vortex generation methods. Resulting effect of passive fluid mixing upon convective heat transfer and hydrodynamic flow phenomena across rectangular micro-channels has been numerically investigated. The effect of increase in Reynolds number upon friction factor and Nusselt number was observed within the laminar flow regime. For this purpose, a combination of vortex generation in the upper region of flow and continuous flow disruption in the lower region was employed using optimized bends/connecting bridge and base corrugation respectively. Significant heat transfer enhancement was achieved through this combined effect. The subsequent work was verified for two independent case studies: 1) Bended-Corrugated channel, 2) Interacting-Corrugated channels. In the first case, an optimized bend generating Dean Vortices was combined with base corrugation, which provided flow disruption effect in the lower region of the channel. For high Reynolds numbers, the overall increase in Nusselt number of up to 32.69% and thermal performance enhancement of upto a maximum value of “1.285 TPF” was observed. For interacting channel model, a connecting bridge of varying width was introduced between adjacent channels for parallel and counter flow configurations, where only the counter flow configuration was found to generate counter rotating vortices. The said model in combination with base corrugation provided an improved performance reaching up to “1.25 TPF”, however as opposed to bended channel, a major decrease in pressure drop of up to 26.88% was observed for this configuration. For both cases, the diverging-converging base corrugation was found to be dependent on width ratio as well as aspect ratio of the corrugation model. The experimentally determined relations for alumina nano-fluids provided by Rea and KKL models were compared for both cases and the Rea model was found to be geometry dependent as opposed to the generalized KKL model.