Turbulent heat transfer and flow analysis of hybrid Al2O3-CuO/water nanofluid: An experiment and CFD simulation study

Abstract

Abstract The utilization of nanofluid is found to considerably enhance the heat transfer performance. The present study fabricated a hybrid Al2O3-CuO/water nanofluid and investigated its turbulent thermal and flow performance in a circular tube. Experimentally, the heat transfer coefficient and pressure drop of hybrid nanofluids with mass concentrations ranging from 0.5% to 3% were measured under different Reynolds number. The effect of selection of thermophysical property models on performance was also concerned. Numerically, Computational Fluid Dynamics (CFD) simulations based on Discrete Phase Model (DPM), mixture and Eulerian multiphase model were conducted and compared. Results reveal a relative enhancement of 2–35% in heat transfer performance of hybrid nanofluid under various flow rates. In addition, the enhancement tends to increase with the increment of nanofluid concentration and decrement of flow rate. The pressure drop also shows different degrees of enlargement up to 12%. Different thermophysical property models lead to different Nusselt and Reynolds numbers, which results to various levels of deviations among different models. Generally, the thermal and flow characteristics adopting different models have similar trend but different magnitudes. By selecting certain models, the thermal performance factor has a value in the range of 1.01–1.29 and shows an increment with the increase of concentration and decrease of Reynolds number. The developed CFD models show desirable prediction accuracies for experimental heat transfer coefficient but seriously underestimate the pressure drop. Specifically, the Eulerian model exhibits the smallest deviation of 8.1% with the experimental heat transfer coefficient followed by the mixture model and DPM with the derivations of 10.2% and 12.5% respectively. The present study can help to understand the heat and flow behaviour of hybrid nanofluid in heat transfer devices.