Numerical and Analytical Investigation on the Influence of Geometry on Thermohydraulic Performance of Single-phase Split Flow Cold Plates for Data Center Liquid Cooling

Split flow impingement micro channel cold plates are being actively deployed in liquid cooling for high heat density data center thermal management. In contrast to the conventional parallel flow scheme, split flow configuration cold plates have a central slot/slit that divides the flow into two branches thus halving the flow rates and flow lengths, which in return reduces the pressure drop and increases the heat transfer coefficient as a result of the influence of the thermally developing flow for shorter flow lengths. In this paper, laminar flow CFD and a new approximate analytical model were utilized to investigate the performance of split flow microchannel cold plates. The effects of jet-slot aspect ratio (ratio of jet-slot width to cold plate channel length), $\beta$ , channel aspect ratio, $\alpha$ , and fin tilt angle, θ, were investigated in detail. The performance of a split flow cold plate and a counterpart geometrically identical parallel flow cold plate was also compared under the same conditions. Results show that increasing the jet slot aspect ratio reduces pressure drop with a slight increase in the thermal resistance. The thermal resistance weakly depends on fin tilt angle, but pressure drop monotonically increase with decreasing fin tilt angle. It is shown that an optimum channel aspect ratio of about $\alpha=12$ minimizes thermal resistance, whereas increasing channel aspect ratio decreased the pressure drop. Results reveal that geometrically identical split flow and parallel flow cold plates have similar thermal resistance, but the split-flow configuration exhibits significantly lower pressure drop.