Numerical study of mixed heat and fluid flow in annuli of heated rotating cylinders

Abstract

Convective flow in the annuli of rotating concentric cylinders were studied through a numerical model. The inner cylinder is heated and rotating in a range of Reynolds numbers where the effects of centrifugal acceleration and three dimensional Taylor vertices are considered negligible. The Prandtl number considered here varies from 0.01 to 1.0 and Rayleigh number varies from 103 to 105. Inner cylinder rotation in the Reynolds number range of 0 to 1120 was considered. Numerical experiments show that the mean Nusselt number increases generally with Rayleigh number. For Prandtl number of the order 0.01 to 0.1, the mean Nusselt number remains fairly constant when the inner cylinder is rotated. Above a critical Rayleigh number, for Prandtl number of order 1.0, when the inner cylinder is made to rotate, the mean Nusselt number decreases through out the flow. For both stationary and rotating cylinders, the flow patterns observed in the annular space are very different for the range of Prandtl number fluids considered here. Mono-thermal plume above the stationary inner was observed for higher Prandtl number fluids while bi-thermal plume above the stationary inner cylinder was observed for lower Prandtl number fluids. When the inner cylinder is made to rotate, the thermal plume for higher and lower Prandtl number fluids moved in different direction.