Turbulent Heat Transfer of Hybrid Nanofluid with Nano-Encapsulated Phase Change Material in a Square Channel

Abstract

Investigation of turbulent mixed convection of different working fluids, namely, pure water, CuO/water nanofluid, n-octadecane/water nanofluid (or slurry), and a hybrid water-based suspension of CuO and n-octadecane nanoparticles in a uniformly heated vertical square channel is carried out. The shear stress transport/kappa-omega model is applied to simulate the turbulent flow. Eulerian–Lagrangian two phase model and homogeneous model are employed to simulate the nanofluid flow. It is shown that Eulerian–Lagrangian two-phase model predicts higher Nusselt number and friction factor than single-phase model and the results of two-phase model are closer to experimental data. It is found that a new hybrid nanofluid with dispersed nano-encapsulated phase change material particles provides better thermal and hydrodynamic performances compared to other nanofluids. Slurry containing 5% n-octadecane provides an improvement of nearly 37.2%, while hybrid nanofluid (1% CuO + 5% n-octadecane) offers added convective heat transfer enhancement of almost 60%. With increasing volume fraction, friction factor becomes slightly larger than that of pure water. For 5% n-octadecane/water and 1% CuO + 5% n-octadecane/water nanofluids, friction factor increases by 2.5% and 1.7%, respectively. Due to dominance of thermal entropy generation, total entropy generation reduces by increasing Reynolds number and volume fraction.