Heat transfer of rotating rectangular duct with compound scaled roughness and V-ribs at high rotation numbers

Local heat transfer measurements for a radially rotating rectangular channel fitted with the compound roughness of staggered V-ribs and deepened scales on two opposite wide walls are performed at the parametric conditions of 10000 <= Re <= 24000, 0 <= Ro <= 1 and 0. 137 <= Delta rho/rho <= 0.274. Heat transfer augmentations achieved by using this compound surface roughness at selected locations along the span and centerline of the leading and trailing walls of the rotating duct are 2.8-5 and 5-7.8 times of the Dittus-Boelter values respectively. No previous attempt has examined the heat transfer performances for such compound surface roughness in the rotating channel with cooling applications to gas turbine rotor blades. A selection of experimental data illustrates the HTE effectiveness with the individual and interdependent Re, Ro and buoyancy number (Bu) effects on heat transfer revealed. Empirical equations that calculate the averaged Nusselt numbers (Nu) over leading and trailing surfaces in the periodically developed flow region are derived to correlate all the heat transfer data generated by present study and permit the evaluation of interdependent and individual effects of Re, Ro and Bu on heat transfer. (C) 2008 Elsevier Masson SAS. All rights reserved.