Numerical simulation of flow boiling heat transfer in microchannel with surface roughness

In order to investigate the effect of surface roughness on the thermal-hydraulic performance of flow boiling in the microchannel, the surface with random roughness is generated by the Fourier series method, the VOF model and Lee model are used to simulate the flow boiling process. The results show that with the increase in relative roughness, Nu and fRe first increase and then decrease. The microchannel with a rough surface can achieve a better thermal-hydraulic performance than that with a smooth surface. Within the scope of this study, the thermal-hydraulic performance reaches the best when the relative roughness is 0.304%. Additionally, with the increase in the means width of the roughness elements, the surface undulation becomes gentler, the growth rate of Nu slows down, and the fRe increases monotonously. Besides, with the decrease in inlet velocity, the liquid film at the bottom of bubbles dries up, which results in drought spots at the bottom wall and deteriorates the heat transfer performance.