Heat Transfer From a Rotating Cylinder With and Without Crossflow

In this paper the problem of convection heat transfer from a rotating cylinder is extended to the case of a cross, or normal flow to the cylinder. Experimental heat-transfer data are presented for a cylinder rotating with and without crossflow. The data for the cylinder rotating with no crossflow are in substantial agreement with the results of previous work, and also with the results of a heat-and-momentum-transfer-analogy solution for convection with no crossflow. Measured temperature profiles in the boundary layer of the heated rotating cylinder are in very good agreement with the analogy solution, and indicate that the boundary layer on a rotating cylinder is quite similar to a turbulent boundary layer on a stationary surface out to about y⁺ = 20. Thereafter a secondary flow becomes the controlling mechanism. The experiments with combined rotation and crossflow indicate two flow regimes; the first for the cylinder peripheral velocity less than twice the crossflow velocity, in which the crossflow provides the controlling effects; the second for the cylinder peripheral velocity greater than twice the crossflow velocity, in which there is a continuous boundary layer around the cylinder and the rotational velocity provides the controlling effects on heat transfer. It is shown that the combined effects of rotation, free convection, and crossflow can be correlated by the equation $NNu=0.135[(0.5NR2+NRs2+NGr)NPr]1/3$ for the rotating Reynolds number in the range 2000 to 45,000.