Elucidating thermal phenomena of non-Newtonian experimental data based copper-alumina-ethylene glycol hybrid nanofluid in a cubic enclosure with central heated plate by machine learning validations of D3Q27 MRT-LBM

Abstract

One of the major challenges in designing an efficient heating and cooling equipment is the consideration and availability of cost-effective fluids. The potential of hybrid nanofluid to replace oil and water in heat exchanging devices has been studied. However, further research is still required to optimise and implement hybrid nanofluids in an industrial setup. This study aimed to investigate power-law non-Newtonian Cu-Al${}_2$O${}_3$-ethylene glycol (EG) hybrid nanofluids in a three-dimensional (3D) cavity, featuring a heated flat plate at the centre, using the Multiple-relaxation-time (MRT) lattice Boltzmann method (LBM). For this purpose, the numerically stable D3Q27 lattices model for the MRT-thermal LBM was employed. The simulation was conducted through parallel computing techniques based on the Compute Unified Device Architecture (CUDA) C++ programming facilitated by NVIDIA GPU. Various governing parameters were considered, including the Rayleigh number ($Ra=10^4,10^5,10^6$), the power-law index ($n=0.8,1.0,1.4$), and the volume fraction of nanoparticles $\varphi$ ranging from 0% to 2%. The model was validated and obtained outcomes were analysed qualitatively and quantitatively. Finally, a cross-validation performance analysis was conducted using a machine learning model and good accuracy was obtained. Some of the key findings suggested that due to the existence of the flat heat radiator, the fluid flow and temperature profiles were distributed from the central position but the upper side of the cavity mostly experienced the greater rate of fluid and heat transfer. Consequently, the velocity of the thermal fluid faced a great obstacle due to the central radiator and temporarily became static. In addition, the $\overline{Nu}$ values were found to be approximately 26.6% greater as $\varphi$ increased from 0 to 0.02 for $n=0.8$ and $Ra=10^6$. Nevertheless, as fluid changed phase from shear-thinning ($n=0.8$) to Newtonian ($n=1.0$), an average reduction of 27% was observed despite considering $\varphi =0.02$ and $Ra=10^6$. To the authors’ knowledge, this was the first study that investigated the flow characteristics and heat transfer phenomena of a non-Newtonian hybrid nanofluid inside a cubic enclosure with a central heated plate. The outcomes from this study would be beneficial in understanding the thermal phenomena of hybrid nanofluid under the influence of a centrally placed heated radiator that could be integrated in thermal heat exchanging device.