Nature-inspired enhanced microscale heat transfer in macro geometry

Abstract

To meet the high cooling demand in the electronics industry, enhanced microchannel heat sinks were introduced. However, the intricacies and high costs associated with microfabrication technologies prove them unsuitable for application in conventional heat exchangers. Hence, the motivation to implement microscale passages in macro geometries ensues. In this study, the annular microchannel is formed by securing a cylindrical insert of mean diameter 19.4 mm concentrically within a cylindrical pipe of internal diameter 20 mm. The paper looks at heat transfer enhancement techniques using inserts of nature-inspired profiles. CFD simulations based on conventional theory were carried out to predict the heat transfer and flow characteristics in the microchannel, for length of 30 mm, mean hydraulic diameter of 600 μm, and under constant heat input of 500 W. Under flow condition of 4 L/min (0.0667 kg/s), convective heat transfer coefficient values of 33.7, 32.7, 30.4 and 26.2 kW/m2·K are obtained for the Durian, Inverted Fish Scale, Fish Scale and Plain profiles respectively. This corresponds to an enhancement of 29%, 25% and 16% respectively, relative to the Plain profile. In addition, using Inverted Fish Scale profile, flow condition of 8 L/min (0.133 kg/s) yield a significant convective heat transfer coefficient value of 59.2 kW/m2·K. The pressure drop values are found to be easily met by a commercially available pump.