Nanoparticle shape effects on thermal-hydraulic performance of boehmite alumina nanofluids in a sinusoidal–wavy mini-channel with phase shift and variable wavelength

Abstract

In this paper, forced convection fluid flow and heat transfer of boehmite alumina – ethylene glycol and water mixture (50: 50) nanofluid in sinusoidal-wavy wall mini-channel with wall phase shift and variable wavelength is studied. The two-dimensional governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. Reynolds numbers are considered in turbulent range of 6, 000 ≤ Re ≤ 15, 000, nanoparticles volume fraction between 0% and 0.04%, nanoparticles diameters from 20 to 60nm and uniform wall temperature is applied on the walls. The optimization was carried out by using different nanoparticle shapes (spherical, spheroidal, platelets, blades, cylindrical and bricks) to reach the optimal nanoparticle shape with the maximum performance evaluation criterion (PEC). From this study, it is concluded that the thermal-hydraulic performance of mini-channel is greatly influenced by changing the shape of nanoparticles. Using spherical and spheroidal nanoparticles improves the thermal-hydraulic performances of mini-channel, while using non-spherical nanoparticle shapes (platelets, blades, cylindrical and bricks) leads to lower PEC in channel than the base fluid. The highest PEC was obtained for the nanoparticle volume fraction of ϕ = 4% by using spherical nanoparticles with diameter of dnp=20 nm at Re = 15, 000. The PEC of this optimum sample at Re=15, 000 is about 1.1489.