The Effect of Aspect Ratio on Hydraulic and Heat Transfer Characteristics in a Fractal Microchannel

The effect of aspect ratio on hydraulic and heat transfer characteristics in the fractal microchannel is investigated numerically and the results are presented in this paper. In the past researches, most researchers studied the effect of channel geometry by varying the channel height for a constant channel width or varying the width for a constant height. In the present work, the effect of aspect ratio is studied by varying the channel width and depth while keeping the inlet cross-sectional area or hydraulic diameter constant. Nine microchannel heat sinks which have different aspect ratios are investigated by numerical simulation. Simulations have been conducted for various values of the inlet velocity covering 5, 6, 7, 8, and 9 m/s and aspect ratio including 1/3,1/2,1, 2, 3. The thermal and hydraulic performances of the fractal microchannels are discussed in terms of the base temperature, Nusselt number, pressure drop and thermal resistance, etc. It is indicated that the aspect ratio significantly affects the hydrodynamic and thermal characteristics of the fractal microchannel heat sink. The enhanced heat transfer is achieved by increasing the aspect ratio of the entrance. The microchannels with lower aspect ratio have bigger pressure drops. The case CCS-(1/3) has medium heat transfer performance and the worst hydraulic characteristics. The microchannel CHD-3 has a better heat transfer performance; meanwhile, it also has relatively small pressure drop.