Heat transfer and entropy generation analysis of three-dimensional nanofluids flow in a cylindrical annulus filled with porous media

Laminar natural-convection flow and entropy production within a vertical porous annulus filled with nanofluids are examined. The vertical walls of the external and internal cylinders are maintained at different temperatures T-H and T-C (T-H > T-C), respectively. In contrast, the bottom and top of the annulus are adiabatic. Equations of continuity, momentum, energy, and entropy are resolved using the finite volume approach. Our FORTRAN-language programming code is well-validated with other works. The effects of porosity 0.2 <= epsilon <= 0.99, nanoparticles 0 <= phi <= 0.08, nanofluid types, Rayleigh 10(3) <= Ra <= 10(5) and Darcy 10(-4) <= Da <= 10(-1) numbers on the flow, heat transfer, and entropy production are examined. We find that nanoparticles' inclusion improves heat transfer and increases total entropy production St. Da and epsilon affect flow structure, thermal field, and entropy generation. Besides, increasing Da and epsilon, St, the average Nusselt Nu(in,out), and Bejan Be numbers increase. However, in the opposite case, St and Be decrease. For Ra = 10(5), the best Nusssetl number is maximum for the Ag-water nanofluid, which increases up to 9.50%. Adding TiO2 nanoparticles, on the other hand, results in a lower Nu(in,out) value. The increase of the inner cylinder size reduces Nu(in,out) and St.

Automated summary

This study examines laminar natural convection flow and entropy production within a vertical porous annulus filled with nanofluids. The inclusion of nanoparticles improves heat transfer and increases total entropy production, while Darcy and porosity numbers affect flow structure and entropy generation. Increasing Da and epsilon values result in higher average Nusselt and Be numbers, while the opposite leads to a decrease in these parameters.