LAMINAR FLUID CONVECTION BETWEEN CONCENTRIC AND ECCENTRIC HEATED HORIZONTAL ROTATING CYLINDERS FOR LOW-PRANDTL-NUMBER FLUIDS

Numerical experiments are performed to study rotational effects on the mixed convection of low-Prandtl-number fluids enclosed between the annuli of concentric and eccentric horizontal cylinders. The inner cylinder is assumed to be heated and rotating. The rotational Reynolds number considered is in the range where the effect of Taylor vortices is negligible. The Prandtl number of the fluid considered is in the range 0.01-1.0. The Rayleigh number considered is up to 10(6). A non-uniform mesh transformation technique coupled with the introduction of 'false transient' parameters to the vorticity and streamfunction-vorticity expressions was used to solve the governing set of equations. Results show that when the inner cylinder is made to rotate, the multicellular flow patterns observed in stationary cylindrical annuli subside in a manner depending on the Prandtl number of the fluids. Eventually the flow tends toward a uniform flow similar to that of a solid body rotation. For a fixed Rayleigh number and with a Prandtl number of the order of 1.0, when the inner cylinder is made to rotate, the mean Nusselt number is observed to decrease throughout the flow. For lower Prandtl number of the order 0.1-0.01 the mean Nusselt number remained fairly constant when the inner cylinder was made to rotate. The mean Nusselt numbers obtained were also compared with available data from other investigators.