Experimental and numerical study of nanofluid flow and heat transfer over microscale backward-facing step

Experimental and numerical studies were presented to reveal the flow and heat transfer characteristics of nanofluid laminar flow over the microscale backward-facing step (MBFS). The duct inlet and the step height were 400 μm and 600 μm respectively. All the walls considered adiabatic except the downstream wall is heated by uniform heat flux. The experiment is conducted at the Reynolds number range from 280 to 470. The distilled water is considered as a base fluid with two types of nanoparticles SiO2 and Al2O3 immersed in the base fluid. The particle diameter is 30 nm and the range of nanoparticles volume fraction in the base fluid varied from 0 to 0.01. The measurement results revealed that the water–SiO2 nanofluid has the highest Nusselt number. It is found also that the Nusselt number increase with increases volume fraction. The water–SiO2 nanofluid with higher volume fraction has the highest Nusselt number. The friction factor of water–Al2O3 was higher than of water–SiO2 mixture. The numerical results were in good agreement with the measurement results.