Flow and heat transfer characteristics in convergent-divergent shaped microchannel with ribs and cavities

Abstract

A computational study has been carried out to examine the effects of ribs and cavities on flow and heat transfer in a convergent-divergent shaped microchannel heat sink with constant heat flux for Reynolds number (Re) ranging from 120 to 900. Three-dimensional governing equations were discretized using the finite-volume method. The computational domain included solid silicon and fluid regions. A significant amount of work has been reported in the literature on the individual effects of channel shape and flow disruption using obstacles on thermal performance of microchannels. In the present study convergent-divergent (CD) shaped microchannel with and without ribs and cavities (RC) are considered and their friction coefficient, thermal resistance and maximum substrate temperature are investigated in detail. The present results show that the usage of CD shape with ribs and cavities can reduce the overall thermal resistance up to 40% and make the bottom surface temperature quite uniform. This heat transfer enhancement is mainly due to interruption and redevelopment of boundary-layers along with recirculation zone. The results also show that increasing Re leads to an enhanced heat transfer in terms of increased averaged Nusselt number from 15% to 46%. The combined effect of CD shape with RC is quite effective in heat transfer augmentation but it gradually loses its effectiveness at large values of Re due to a high pressure drop penalty.

Experimental Investigation of Microchannel Heat Sink with Modified Hexagonal Fins

“…The thermal resistance of microchannels with ribs is found to decrease from 4 to 31% when compared with the straight fin microchannel heatsink. Convergent-divergent shaped microchannels with or without rib cavities have been simulated by Srivastava et al (2017). The introduction of convergent-divergent ribs and cavities was found to reduce the overall thermal resistance by 40% and make the heatsink surface temperature uniform.…”

Heat transfer correlation for a triangular protruded surface with a cross-flow jet

“…Figure 11(b) shows the variation of ff with Re Dh;duct . From Re Dh;duct ¼ 17; 827 À 26740, a sharp decrement in ff has been noticed, and thereafter it decreases asymptotically for other Reynolds number (i.e., 35,480). When Re Dh;duct is increased, the denominator of Eq.…”

“…Generally, the flow past an obstacle is unsteady due to the presence of wakes generated due to flow recirculation. The unsteadiness is more severe while simulating a thermal buoyant plume [34,35] past an obstacle at high Rayleigh number. For such flows it is always preferred to use unsteady RANS (U-RANS) instead of steady RANS (S-RANS), and the U-RANS would be one of the better choices for quantifying the mean quantities, especially the prediction of normal and shear stresses [36,37].…”

A study of turbulent heat transfer in convergent-divergent shaped microchannel with ribs and cavities using CFD

“…Further the effects of ribs and cavities present in the fluid domain, which interrupt the boundary layers, on flow and heat transfer characteristics, are analysed. The present authors have earlier carried out an investigation on the effects of the channel shape with different flow disruption techniques for a laminar flow and have also studied combined effects of shape change and flow disruption [6]. A similar study for turbulent flow has not been reported, which motivated the present authors to carry out this study.…”

“…They showed that thermal performance could be improved by using a narrow and deep channel with thin bottom surface thickness with a high but acceptable pumping power. Srivastava et al [6] investigated the effects of ribs and cavities on convergent-divergent shaped microchannel in laminar flow condition and showed that a uniform and lower substrate temperature could be achieved with a lower pressure drop penalty. Duryodhan et al [7] performed experimental investigation on the shape of a microchannel and concluded that a converging microchannel had a better performance compared to a diverging one under similar conditions.…”