Parametric design analysis of a multi-level 3D manifolded microchannel cooler via reduced order numerical modeling

Abstract

Waste heat flux from power dense electronics is expected to reach > 1 kW/cm2 in the next few decades, and they will require novel cooler designs with low thermal resistance, that can simultaneously dissipate large levels of heat and have high coefficient of performance (COP). 2D straight microchannel cold plates (CP) are an industrial go-to solution for active heat dissipation needs, but they suffer from a major drawback – very high pump pressure is required to force large quantities of fluid through miniscule channels in the CP and thus these coolers are very inefficient, achieving low COP. Recently, manifolded micro-coolers (MMC) have become popular which use a second manifold layer to distribute the fluid in 3D within the CP, thus shortening fluid travel length within the miniscule CP channels and significantly reducing the total device pressure drop. In this study, we first introduce a novel two-level manifold design which boasts a potential of > 2x improvement in COP compared to conventional single-level manifold concept without affecting the thermal performance. Recognizing the difficulty in simulating large area full MMCs, we then aim to simplify the 2-level MMC geometry into reduced order models to bring down simulation cost at an expense of accuracy. Two models were considered, the widely popular and convenient to use Single Cold Plate U-bend Channel (SCPUC) model which only simulates the CP channels, and the slightly more complicated Single Manifold Channel (SMC) model which also considers the effect of the manifold. The SMC model simulations were first validated against full device simulations for different heater footprint sizes (25, 100, 400 mm2) to establish accuracy and it was found that the SMC model could predict thermal performances of all device sizes with a nominal inaccuracy of 5%. In contrast, the widely accepted SCPUC model produced highly inaccurate (as high as 25–45%) predictions for thermal performance of the MMCs. The two models were then used under an extreme heat flux load of 800 W/cm2 and 0.2 liter per min (lpm) device flow rate, to simulate 54 different 2-level MMCs obtained by varying important geometric parameters on the manifold and cold plate side. Detailed analysis was performed to explain the trends in thermal performance and pressure drop with different geometric parameters. Finally, two pareto curves were reported, one between thermal resistance and pressure drop, and the other between COP and device size. It was seen that the proposed 2-level MMC showed record high COP as compared to state-of-the-art single-level MMCs. We hope that this study will act as a design guide for MMCs as well as act as a performance repository for a wide range and combinations of geometries of 2-level manifold structures.