Augmentation of Heat Transfer and AL2O3-Nanofluid Flow Over Vertical Double Forward-Facing Step (DFFS)

Nanofluids are recommended to improve heat transfer in cooling and heating systems, resulting in significant benefits. This paper numerically investigates turbulent heat transfer and Al2O3-nanofluid flow over a vertical double forward-facing step. A two dimensional with three different cases of vertical DFFS is conducted using K-ɛ model based on finite volume method for volume fraction of nanofluids varied for 1%, 2% ,3% and Reynolds number changed from 10000 to 40000. With increasing Reynolds number, there is an increase in local coefficients of heat transfer, with the highest coefficient of heat transfer detected at Re=40000. For volume fractions of Al2O3= 3% and Reynolds numbers of 40000, the effects of step height on surface coefficients of heat transfer are described. In addition, the findings have discovered that as the volume fraction of Al2O3 nanofluids has increased, the coefficient of heat transfer has increased as well, with the maximum coefficient of heat transfer occurring at a volume fraction of Al2O3 nanofluids of 3%. Furthermore, the first step-case 2 local coefficient of heat transfer has been higher than the first step-cases 1 and 3. Increased Re number causes a sharp drop in local static pressure at the first and at the second steps. Due to the recirculation flow, there has been a reduction in velocity profile near the first and second steps, indicating an increase in heat transfer rate. Moreover, velocity counters are shown in order to demonstrate how Reynolds number affects the size of the recirculation zone. In addition, the turbulence kinetic energy counter has been shown in order to demonstrate how to achieve thermal efficiency in the second step in all the cases.