Heat transfer in rotating scale-roughened trapezoidal duct at high rotation numbers

An experimental study of heat transfer in a radially rotating trapezoidal duct with two bevel walls roughened by deepened scales is performed with cooling applications to gas turbine rotor blades. Laboratory scale heat transfer data along the centerlines of two scale-roughened walls is generated within the parametric ranges of 7500 ⩽ Re ⩽ 15,000, 0 ⩽ Ro ⩽ 1.8 and 0.13 ⩽ Δρ/ρ ⩽ 0.42. No previous study has examined the heat transfer in a rotating scale-roughened channel and the present Ro range extends considerably from other researches to date. A selection of experimental data illustrates the individual and interactive impacts of Re, Ro and buoyancy number (Bu) on local heat transfer through which the manners of isolated and synergetic influences of Coriolis force and rotating buoyancy on heat transfer are examined. Local Nusselt number ratios between rotating and static channels on the stable (leading) and unstable (trailing) scale-roughened surfaces with Ro varying from 0.1 to 1.8 fall in the ranges of 0.8–2 and 1.1–2.5, respectively. Rotating buoyancy effects are weakened as Ro increases that impair local heat transfer for the present test configurations. Empirical heat transfer correlations for developed flow regions on two scale-roughened surfaces are derived that permit the evaluation of interactive and individual effects of Re, Ro and Bu on local heat transfer.