Large eddy simulations of a turbulent flow with hybrid nanofluid subjected to symmetric and asymmetric heating

The present study includes a comprehensive numerical analysis of the usage of nanofluids inside a thermal receiver to assess the possibility of enhancing the efficiency of this device. All simulations are performed on a small portion of a thermal receiver, similar to a bi-periodic channel subjected to symmetric and asymmetric heating. To generate conventional and hybrid nanofluids, nanoparticles of Al2O3 and Al2O3-Cu are dispersed in the base fluid H2O. The values of nanoparticles' diameter is 20nm and volume fraction of the nanoparticles is 2%. The Reynolds numbers used in this study are 12 000 and 18 000, which respectively correspond to mean friction Reynolds numbers of 140 and 260. The thermal Large Eddy Simulation (T-LES) approach is used to simulate the fluid flow and heat transfer inside the computational domain. The results are compared with those of prior numerical and experimental studies to validate the method and the numerical setup. A high level of agreement is achieved. In the case of symmetric and asymmetric heating, the dimensionless findings reveal that adding nanoparticles to the base fluid has a negligible impact on the velocity fluctuations. Nanoparticles make the base fluid denser and more viscous but also more conductive, allowing it to minimize kinetic energy while boosting heat transfer rate. Results also show that using hybrid nanofluids contributes better to improving the heat transfer rate compared to the base fluid and the conventional nanofluid. Introducing nanoparticles into the base fluid decreases its temperatures slightly, especially when Al2O3-Cu nanoparticles are used instead of Al2O3 nanoparticles. In the asymmetric case, water's turbulent heat flux values are greater than nanofluids and hybrid nanofluid, implying that more conductive and viscous liquids have the weakest turbulent heat flux. In the circumstances of symmetric and asymmetric heating, the variation of the velocity fluctuations is almost the same, but the behavior of the temperature–velocity correlation is entirely different. Finally, results show that symmetric heating leads to a higher heat transfer rate than asymmetric heating. The suggested research's findings may be utilized to promote the usage of nanofluids in Concentrated Solar Power (CSP) systems.