Secondary Flow Effects in High Tip Speed Free Convection

Abstract

Experimental analyses of the effects of secondary flows on heat transfer in high tip speed rotating apparatus are not readily available. This paper provides data on the heat transfer within two different test modules which were rotated at high speed with the heat transfer surfaces perpendicular and parallel to the Coriolis acceleration. One module contained a heated wall and another a parallel plate free convection experiment. Uniform heat fluxes were maintained. Rayleigh numbers in excess of 1015 were achieved with liquid helium as the transfer medium. Some of the findings are that secondary flows can reduce heat transfer by as much as 60 percent in single-phase heat transfer, the transitions to fully turbulent flow are in agreement with existing prediction methods, the critical heat flux in two-phase flow boiling is significantly increased, forced convection correlations underpredict single-phase thermosyphon performance, and the usual nondimensional parameters of free convection establish similitude between various fluids and speeds. These results suggest that techniques used to enhance heat transfer in the rotating frame should be verified by tests in the rotating frame.