Evaluating heat transfer and pressure drop in circular multiple impingement jets using hybrid nanofluids

Abstract

Utilisation of multiple impingement jet cooling structures is a prevalent practise in various industrial applications, including gas turbine engines, with the primary objective of augmenting heat transfer. The numerical procedure entails using Computational Fluid Dynamics (CFD) techniques to simulate the flow and heat transfer characteristics within the impingement region. The governing equations for fluid flow and the heat transfer are discretized using finite volume method on a structured grid. The turbulence effects were represented using SST k-omega model. Al₂O_3-Cu / water with different volume fractions (${\phi }_{\mathrm{hnf}}$) such as 0.1 %, 0.33 %, 0.75 %, and 1.0 % are employed as a working fluid. The purpose of the study is to clarify the impact of the jet angle (β), the jet Reynolds number (Re), extended jet height ${(E}_j$), and different volume fraction (${\phi }_{\mathrm{hnf}}$) on the heat transfer behaviours of the curved target surface. The jet Reynolds number varies from 8,000 to 24,000, and five different jet angles (β = 15 ${}^{°}$, 30°, 45°, 60°, 90 ${}^{°}$) and three extended jet heights${(E}_j$ = 0.2H, 0.4H, and 0.6H) are adopted. Within the range of studied parameters, the maximum Nusselt number occurs at the highest value of ${\phi }_{\mathrm{hnf}}$ at all values of Re. The heat transfer rate and pressure drop of the system are enhanced significantly by the highest values of Re and ${\phi }_{\mathrm{hnf}}$. For all jet angle and Reynolds number, the heat transfer rate of binary hybrid nanofluids improve with the increase of volume fraction. The angle of jet, 45°, in this study gives a higher Nusselt number than other jet angles and the maximum is 29 %. Placing axial jet at a height less than maximum Nusselt number of a 90° extended jet will enhance heat transfer rate in comparison with other methods, while simultaneously, increases pressure drop.