Tip Clearance Effects on Microchannel-Based Heat Sink with Polymeric Fluid

摘要

This article describes an experimental study on the influence that tip clearance exerts on heat transfer and pressure drop when a power law non-Newtonian fluid (hydroxyethyl cellulose at 0.1, 0.25, and 0.5% mass fractions) passes through a microchannel-based heat sink. This problem is of practical interest for engineering systems in which both heat transfer and pressure drop (directly related to pumping power) have to be considered simultaneously in the design. The results obtained for the power law fluid show that the presence of tip clearance contributes to decrease significantly the pressure drop at the expense of a small reduction in the heat transfer rate. Additionally, a figure merit for each configuration that combines the heat transfer rate and the pumping power has been defined. It has been found that this figure of merit improves by a factor in the range of 20-50% (depending on the configuration) when a tip clearance is implemented. In practice, all this means that the scope of applications for tip clearance bypass flows (well known in Newtonian flows) also encompasses non-Newtonian flows, thereby broadening the number of industrial sectors in which heat-transfer-related problems may benefit from this effect.