Numerical investigation of semi-confined turbulent slot jet impingement on a concave surface using an Al2O3–water nanofluid

• Using the nanofluids leads to higher rate of heat transfer from a concave surface.
• The increase of particle concentration increases the thermo hydraulic performance.
• The maximum average Nusselt number occurs around h/B = 5 in concave surface.
• The increase of pumping power is the unfavorable effect of using the nanofluids.

This paper presents and discusses results of a computational study of the flow field and heat transfer characteristics for a turbulent slot jet of an Al2O3–water nanofluid impinging normally on to a semi-circular concave surface. A wide range of various flow and geometrical parameters, including the nanoparticle volume fraction (Φ), jet Reynolds number (Re), and jet-to-target distance (h/B) have been considered. The results are presented in terms of the streamline patterns, local and average Nusselt numbers, stagnation Nusselt number, shear stress distribution, and pumping power. The results show a significant improvement of heat transfer rate due to the presence of the nanoparticles in water. Moreover, for ratios of h/B greater than three, the maximum average heat transfer rate from the concave surface occurs at h/B = 5. An increase in the jet Reynolds number and nanoparticle concentration leads to an improved cooling performance of jet impingement on the concave surface. However, the elevated viscosity of the nanofluid has the adverse effect of increasing the pumping power needed per unit of heat transferred.