Computational optimum design of natural convection in a concentric and eccentric annular cylinder using nanofluids

Free convection of various nanofluids inside concentric and eccentric annular cavity with internal heat flux, fully filled with porous media is studied numerically and its heat transfer rate and pressure drop are examined. The impact of inner cylinder inclination angles (βecc = 45^°, 135^°, 225°, and 270^°) and nanofluids (Al₂O₃/water, CuO/water and SiO₂/water) for different heat flux (1000, 2000, 3000, and 4000 w/m²) on the heat transfer rate are evaluated. Initially, a validation process has been implemented to ensure that the predicted results obtained from this model are accurate. Results indicate that Al₂O₃ Nanofluid provides a better enhancement in the heat transfer rate when compared to SiO₂ and Cu Nanofluids. Furthermore, the heat transfer coefficient increased with the inclination angle of βecc = 225^°, and maximum heat transfer occurred at a heat flux of 4000 W/m², which was roughly 6% greater than the concentric annular cylinder. The findings also indicated that while increasing the eccentricity has a minor impact on the heat transfer rate for convection-dominated flows (high heat flux), on the other hand, it has a significant impact on the heat transfer rate for conduction-dominated flows (low heat flux).