Forced convection cooling of additively manufactured single and double layer enhanced microchannels

Abstract

Abstract Metal based additive manufacturing (AM) is gaining increasing attention in the thermal management community due to the ability to fabricate intricate internal cooling features with acceptable accuracy. The non-traditional designs possible with AM can be leveraged to fabricate enhanced microchannel geometries which allow removal of high heat fluxes from power electronic devices. This study thereby explores the marriage of additive manufacturing and microchannel cooling where microchannels are fabricated using Direct Metal Laser Sintering (DMLS). Microchannels arranged in single layer and double layer configurations are evaluated for their heat transfer and pressure drop performance over Reynolds number, based on channel hydraulic diameter, ranging from 200 - 900 with water as the coolant. The double layer microchannels present a more complex geometry, with two layers of microchannels stacked one on top of the other which promises improved thermal performance based on literature. Enhancement features in the form of periodic oblique and alternating oblique secondary channels, known to augment fluid mixing and disrupt boundary layer growth are incorporated in both configurations aimed at augmenting the overall performance. Seven AM microchannel geometries, three in single and four in double layer configurations are tested. AM parts analyzed for their surface roughness and dimensional accuracy exhibit high surface roughness and deviation from design intent dimensions. Straight microchannel, fabricated using conventional manufacturing where the channel walls exhibit lower roughness levels serves as the baseline case. Comparing the performance of straight microchannels fabricated via conventional and additive methods reveal roughness induced augmentation in heat transfer and pressure drop of about 10-15%. Incorporation of secondary flow channels results in enhanced thermal hydraulic performance in both single and double layer configurations. Microchannels ranked based on thermal-hydraulic performance show double layer microchannel featuring oblique secondary channels offering the best performance with ~60% higher performance than baseline. The findings from this study highlight the potential of AM in developing sophisticated microchannels.