High aspect ratio microchannel heat sink optimization under thermally developing flow conditions based on minimum power consumption

Abstract

• Aspect Ratio (AR) has a crucial effect on the heat sink (HS) thermal performance. • High AR leads to a better performance up to an optimal value in HS design. • Working in Thermally Developing (TD) region improves the thermal performance of HS. • Experimental Nu numbers in TD region are higher than theoretical values. • Nu number highly depends on Re number in the TD region. In electronics cooling, it is vital to remove a high amount of heat from electronic components within a confined space to keep the temperature below a required limit and to increase the lifetime of these components as well as their performances. While there are many studies on microchannel heat sinks for these purposes, studies on the working fluid of Ethylene Glycol Water (EGW) on thermally developing flows in high aspect ratio rectangular channels are rather scarce. In this study, the goal is to achieve an optimum heat sink design by considering both thermal performance and power consumption and keeping the cooling volume as small as possible. Optimization efforts were parametrically made using the Finite Volume Method to find the temperature distribution and flow rate for the selected pressure drop values within the single microchannel. The base area of the microchannel heat sink (Al 6063-T05) was kept constant, while the heat flux value of 100 W/cm 2 was selected as the cooling target in parallel lines with the heat removal requirements in electronics cooling. Except for the channel length, all parameters including channel spacing, channel height, and channel thickness were considered in the optimization. Rectangular channel configurations with a hydraulic diameter (D h ) of 193–375 µm and aspect ratios of 2.5–25 were analyzed at different Reynolds numbers (Re) and pressure drop values in the ranges of 13–360 and 10 kPa–50 kPa, respectively. In this study, EGW was preferred as the working fluid due to its superior thermal performance and low freezing point. After performing a comprehensive CFD analysis to determine the optimum channel geometry, the optimized microchannel heat sink (MCHS) was manufactured by using the Electrical Discharge Machining (EDM) technology, and its performance was experimentally assessed at different Re numbers. There was a good agreement between the numerical and experimental results, and the optimized MCHS could serve for the applications, where the number of heat sources is high and parallel cooling needs to be applied to have a uniform temperature distribution among the sources.