Entry region heat transfer in rotating radial tubes

An experimental study of the effect of rotation on the entrance region heat transfer inside straight, radially aligned circular tubes is presented. Average coolant passage Nusselt numbers were determined for passage length-to-diameter ratios of 6, 12, and 24 over ranges of radially outward air flows and rotational speeds. Results are presented in terms of the ratio of rotating-to-stationary heat transfer. Comparisons are made with the rotational heat transfer enhancement expected for fully developed flow conditions with rotation. The present results, conducted in the absence of entry swirl, show that only a small rotational effect on heat transfer can be expected for relatively short cooling passages.