A Numerical Investigation of Heat Transfer Enhancement Techniques in Mini-channel Heat Sink

With the advancement of sophisticated technology, it has become a prime concern to design electronic and mechanical equipment having a very compact assembly. The cooling technology associated with such equipment has become one of the bottleneck problems. Mini-channel heat sink having the benefit of high surface area to volume ratio could be the solution for effective heat transfer in the miniature devices. However, the pressure drop penalty of this mini-channel heat sink is significantly high. The thermal performance of the mini-channel profoundly depends on the geometry and its arrangement like shape of the cross sectional area, channel flow path, surface roughness, obstacles in the flow direction etc. Flow with redeveloping thermal boundary layer results in higher heat transfer rate. In this research work, several heat transfer enhancement techniques have been studied numerically considering redeveloping boundary layer. Rectangular mini-channel having a hydraulic diameter of 1.53 mm has been considered in this study. Air is taken as the working fluid which is supplied to the heat sink at an inlet temperature of 293 K and at velocity of 0.7 m/s, 1.2 m/s, 1.5 m/s, 2 m/s and 2.5 m/s. Temperature of the bottom surface of the channel is kept fixed at 340 K. The thermal performance of the mini-channels have been evaluated and compared based on Nusselt number, thermal resistance and pumping power requirements. Once the simulation is completed for the conventional mini-channel, the channel has been modified by incorporating different heat transfer enhancement schemes, like introducing bump of different size inside the channel, implementing cross connection of the channels by placing converging or diverging nozzles side by side. From the numerical results, it has been found that introduction of bump enhances heat transfer rate compared to the simple rectangular channel. Modifications of the channel with the converging or diverging nozzle and cross connection between channel and nozzle introduce cross flow of the coolant at a higher rate compared to the rectangular mini-channel, resulting in increased Nusselt number compared to the all of the configurations. Requirement of the pumping powers for the converging and diverging arrangements are found higher than the conventional rectangular mini-channel in order to ensure the same thermal performance.