Influence of structured surface roughness peaks on flow and heat transfer performances of micro- and mini-channels

The effect of surface roughness peaks (SRP) on laminar air-flow and heat transfer performances in rough microand mini -channels is analyzed by 3D computational fluid dynamics (CFD) simulation method. The variations of channel height, SRP height, pitch and width, aligned and off-set SRP, and hybrid SRP in rectangular channels are studied. The parametric ranges of channel height, SRP height and constricted diameter of the channel are 150 pm to 400 pm, 15 pm to 45 pm, and 179 pm to 663 pm, respectively. The results showed that heat transfer performance of smooth micro- and mini-channels with low aspect ratio is higher than the conventional predictions. The maximum convective heat transfer depends on the optimum combination of channel size and roughness height. Furthermore, increasing SRP pitch has less impact on the heat transfer while increasing roughness width improves the performance index. Hybrid SRP in a channel is more effective than constant SRP at lower Reynolds number with the performance index improved up to 12%. Aligned peaks are more efficient than the off-set arrangement and the average rise of performance is 9% under present conditions. Relative roughness with varying parameters can be configured for practical purposes without compromising the compactness.