Effect of channel aspect ratio and fin geometry on fluid flow and heat transfer performance of sectional oblique fin microchannels

Abstract

Single-pass micro-channel heat sinks (MCHS) with water as the working fluid have been shown to deliver large heat removal rates with marginal pressure drop penalty. MCHS, because of their high surface area to volume ratio, provide large heat transfer coefficients (HTC) not found in other macro-scale channels and have found applications in power electronic devices and aerospace heat exchangers. Micro-channels with sectional oblique fins in the same direction augment heat transfer by reinitializing the boundary layer at the leading edge of each fin, causing the flow to be in a developing state, resulting in improved thermal performance. A detailed numerical study has been carried out on oblique fin microchannel heat sinks (OMC) to investigate the impact of channel aspect ratio (AR) and fin-pitch to oblique channel width ratio (BETA) on heat transfer and fluid flow characteristics. OMC with an aspect ratio ranging from 0.25 to 1, followed by four BETA values between 4 and 8, have been tested. Results reveal that OMC with AR of 0.6 outperforms the other configurations. A trade-off has been established where taller fins, although providing higher heat transfer area, suffer from poor fin efficiency, significantly impacting Nusselt number. OMC with BETA up to 6 has been shown to have similar hydro-thermal performance. The existing interplay between increasing mean channel velocity and decreasing heat transfer area has been identified at large hydraulic diameters.