Experimental Investigation of Heat Transfer Enhancement for CuO and Graphene Nanofluids in Corrugated Backward-Facing Step Channels with Obstacle

The friction factor and heat transfer rate of CuO-water and GO-water nanofluids on a backward-facing step (BFS)channel with trapezoidal corrugated walls and obstacle are experimentally studied by forced convection. Nanoparticles of CuO and Graphene were dispersed in water at volume concentrations of 0.1-1.0%. Tests were performed in turbulent flow in the Reynolds number range from 5000 to 20,000 at uniform heat flux of 40 kW/m². Nusselt number (Nu) increases with Re and concentration of nanoparticles. At Re = 20,000 and the concentration of 1.0% of nanofluid, the Nu of graphene-water nanofluid was 194, which is about 17% greater than that of water; meanwhile, the Nu of CuO-water nanofluid was 185 which is better than water by 12%. The friction factor also increased with nanoparticles loading and they obtained about ~35% higher and ~40% higher than water for CuO and graphene, respectively at Re = 5000. At low Re, the maximum performance evaluation criterion (PEC) of 0.5% graphene and 1% CuO was 1.74 and 1.58%, respectively, confirming the high thermal-hydraulic performance of graphene in the BFS channel.