Numerical investigation of entropy generation and double-diffusive natural convection for nanofluid flow inside a hexagonal enclosure with different hot obstacles

In this paper, a simulation is performed on nanofluids flow with double-diffusive natural convection. The enclosure is hexagonal, and hot obstacles of various shapes are placed inside it. The partial differential equations governing fluid flow and heat and mass transfer are solved using the finite element method. Mass diffusion, characterized by the Lewis number (Le), is a significant parameter affecting the behavior of two-phase flow. This parameter is the most influential parameter in concentration distribution. Temperature, velocity, and concentration fields inside the enclosure are analyzed using temperature, velocity, and concentration contours. The results of this study show that increasing the Le from 1 to 5 causes a reduction in the \(\overline{{{\text{Nu}}}}\) by 11.23%, 11.7%, 11.95%, and 11.03% and an increase in the \(\overline{{{\text{Sh}}}}\) by 64.41%, 70.82%, 69.64%, and 69.60% for circular, triangular, rectangular, and rhombus obstacles, respectively. Increasing the aspect ratio (AR) from 0.1 to 0.3 leads to an increase in the \(\overline{{{\text{Nu}}}}\) by 49%, 36%, 33.7%, and 45.3% and an increase in the \(\overline{{{\text{Sh}}}}\) by 48.8%, 39.4%, 44.3%, and 47.6% for circular, triangular, rectangular, and rhombus obstacles, respectively. The average Be decreases with an increase in the AR and increases with an increase in the Le. Increasing the Le leads to a decrease in fluid entropy generation (ENT) and total ENT but increases the AR, which increases fluid ENT and total ENT. However, the change in both thermal ENTs did not result in any significant change.