Passively Enhanced Natural Convection Heat Transfer via Swirl Effect

Abstract

A numerical and experimental study of the free convective heat transfer rate from a heated circular disk experiencing swirling flow has been carried out using ANSYS Fluent and a Mach Zehnder Interferometer (MZI). A horizontal, flat, isothermal disk has been subjected to radially swirling flow by the placement of stationary angled blades, or vanes, around the circumference of the disk. An examination of the flow pattern on a plane approximately normal to the primary flow revealed regions of downwash and upwash near the surface of the disk. The vortices in the secondary flow generated areas of increased and decreased surface heat flux corresponding to the regions of downwash and upwash, respectively. The RNG kepsilon turbulence model was used to obtain the disk's overall Nusselt number for 1.28x10 6 ≤ RaD ≤ 2.56x10 8. The numerical model was used to compute and compare Nusselt numbers between vane designs of varying height, angle, length, thickness, and number. Preliminary vane design recommendations are made. Results show passive natural convection heat transfer enhancement of up to 35% via the swirl effect when compared to the model with no swirl.