Heat transfer and pressure drop measurements of rotating twin-pass parallelogram ribbed channel

Abstract

Heat transfer characteristics, Fanning friction factors (f) and thermal performance factors (TPF) of a radially rotating twin-pass ribbed channel with parallelogram cross-section are presented. No previous study has examined the thermal performances in such a parallelogram channel. Laboratory scale full field Nusselt number (Nu) distributions over leading and trailing ribbed walls of the rotating channel were measured for Reynolds number, rotating number, and density ratio of 4000 ≤ Re ≤ 10,000, 0 ≤ Ro ≤ 0.4 and 0.042 ≤ Δρ/ρ ≤ 0.14, respectively. It is found that the analyzed results can illustrate the individual and interactive impacts of Re, Ro and buoyancy (Bu) numbers on local and area-averaged heat transfer performances. Specifically, with a set of f correlations generated using the f data detected from the ribbed walls and sidewalls at isothermal conditions, the TPF values at various rotating conditions are evaluated. The heat transfer correlations that determine the area-averaged Nusselt numbers over the inlet and outlet channels with radially outward and inward flows, respectively, as well as over the turning region are generated to permit the evaluation of interactive and individual effects of Re, Ro and Bu on heat transfer performances. The combined Re, Ro and Bu effects on heat transfer and friction augmentations for the present test channel raise the TPF values to the range of 1.77–3.06, indicating the efficiency of the rotating ribbed twin-pass parallelogram channel as an efficient HTE measure for turbine rotor blade cooling.