Numerical Investigation of Natural Convection and Irreversibilities between Two Inclined Concentric Cylinders in Presence of Uniform Magnetic Field and Radiation

Abstract

In this study, the free convection with volumetric radiation in a water–alumina nanofluid flowing between two inclined concentric cylinders was simulated. The enclosure, or the cavity between the two circular quadrants in which the inner and outer pipes were respectively at high and low temperatures, was exposed to a magnetic field, and the remaining walls were insulated. Simulations were performed using control volume and the SIMPLE algorithm. The effects of the Rayleigh and Hartmann numbers, cavity or enclosure angle, magnetic field angle, nanopowder volume fraction, radiation intensity, and aspect ratio were investigated on the Nusselt number, irreversibilities and the Bejan number. According to the results, the Rayleigh number, hot pipe diameter, and adding more nanopowder have increasing and the Hartmann number has decreasing effect on the thermal performance and irreversibilities. Adding more nanopowder and increasing the enclosure angle also improved heat transfer. Increasing the magnetic field angle first increased and then decreased irreversibilities. In fact, increasing the magnetic field angle increased up to 15°, the heat transfer rate increased, and further increase of the magnetic field angle from 15° to 90° decreased the heat transfer rate.