Combined Natural and Forced Convective Heat Transfer In Spherical Annuli

Abstract

This paper presents numerical finite difference solutions of combined natural and forced convective heat transfer in spherical annuli. The flow is assumed to enter the annulus through a port in the bottom of the outer sphere and exit through a diametrically opposite port. The spheres are isothermal and at different temperatures. The governing conservation equations are reduced to dimensionless form and the nondimensional parameters of the problem are identified. The influence of these parameters of the problem are identified. The influence of these parameters on the solution is studied. Details of the flow field and temperature field are presented by means of velocity vector and isotherm maps. Circumferential average and local Nusselt numbers are presented and compared with earlier numerical work in which the effects of natural convection were ignored. It is shown that the buoyancy effects can have a very significant impact on the heat transfer and fluid flow, particularly at low Reynolds numbers.