Effects of jet pattern on single-phase cooling performance of hybrid micro-channel/micro-circular-jet-impingement thermal management scheme

This study explores the single-phase cooling performance of a hybrid cooling module in which a series of micro-jets deposit coolant into each channel of a micro-channel heat sink. This creates symmetrical flow in each micro-channel, and the coolant is expelled through both ends of the micro-channel. Three micro-jet patterns are examined, decreasing-jet-size (relative to center of channel), equal-jet-size and increasing-jet-size. The performance of each pattern is examined experimentally and numerically using HFE 7100 as working fluid. Indirect refrigeration cooling is used to reduce the coolant’s temperature in order to produce low wall temperatures during high-flux heat dissipation. A single heat transfer coefficient correlation is found equally effective at correlating experimental data for all three jet patterns. Three-dimensional numerical simulation using the standard k–ε model shows excellent accuracy in predicting wall temperatures. Numerical results show the hybrid cooling module involves complex interactions of impinging jets and micro-channel flow. Increasing the coolant’s flow rate strengthens the contribution of jet impingement to the overall cooling performance, and decreases wall temperature. However, this advantage is realized at the expense of greater wall temperature gradients. The decreasing-jet-size pattern yields the highest convective heat transfer coefficients and lowest wall temperatures, while the equal-jet-size pattern provides the greatest uniformity in wall temperature. The increasing-jet-size pattern produces complex flow patterns and greater wall temperature gradients, which are caused by blockage of spent fluid flow due to the impingement from larger jets near the channel outlets.