Nusselt Number Correlations for Forced Convection in a Microchannel Including Discrete Heat Sources

Using the finite volume scheme, a two-dimensional rectangular microchannel heat sink (MCHS) with discrete heat sources on top and bottom walls in the laminar flow regime was investigated numerically. Water and three homogenous nanofluids (Al2O3-water, TiO2-water, and CuO-water) were considered as the working fluids. To assess the effect of the location of discrete heat sources on thermal performance of the MCHS, a parameter called PFF (percentage of being face to face of the discrete heat sources), which determines to what extent the faces of discrete heat sources on top and bottom walls are in front of each other, was introduced. The findings showed that the effect of halving the Reynolds number on an increase of dimensionless temperature along the channel axis was greater than that of doubling the volume fraction of nanoparticles. Also, when the Reynolds number increases, the effect of PFF on the average Nusselt number reduces. Moreover, the nanofluid temperature along the centerline was maximum when the heat sources were located opposite to each other and minimum when arranged in a staggered pattern. Finally, correlations for calculating the average Nusselt number on the top and bottom walls as a function of PFFs and Reynolds numbers were proposed.