TOWARD IMPROVED HEAT DISSIPATION OF THE TURBULENT REGIME OVER BACKWARD-FACING STEP FOR THE Al₂O₃-WATER NANOFLUIDS: An Experimental Approach

Experimental study of nanofluid flow and heat transfer to fully developed turbulent forced convection flow in a uniformly heated tubular horizontal backward-facing step has reported in the present study. To study the forced convective heat transfer coefficient in the turbulent regime, an experimental study is performed at a different weight concentration of Al2O3 nanoparticles. The experiment had conducted for water and Al2O3 water nanofluid for the concentration range of 0 to 0.1 wt. % and Reynolds number of 4000 to 16000. The average heat transfer coefficient ratio increases significantly as Reynolds number increasing, increased from 9.6% at Reynolds number of 4000 to 26.3% at Reynolds number of 16000 at the constant weight concentration of 0.1%. The Al2O3-water nanofluid exhibited excellent thermal performance in the tube with a backward facing step in comparison to distilled water. However, the pressure losses increased with the increase of the Reynolds number and/or the weight concentrations, but the enhancement rates were insignificant.