Cavity Heat Transfer on a Transverse Grooved Wall in a Narrow Flow Channel

Measurements are presented of local convection heat transfer for the case of flow through a narrow slot-type channel where one of the bounding walls contains a transverse rectangular cavity. The experimental situation is a stationary modeling of some salient features of flow through the clearance gap at the grooved tips of axial turbine blades. Cavity depth-to-width ratios of 0.1, 0.2, and 0.5 are included for each of clearance-to-width ratios of 0.05, 0.10, and 0.15. Overall heat transfer on the cavity floor is in general reduced as cavity depth is increased, but reduction with the deepest cavity tested is essentially the same as that of the intermediate depth cavity. Resistance to flow through the gap is increased as cavity depth is increased, but again the change between the deepest and intermediate depth cavities is small. In addition to the stationary experiments, heat transfer in the cavity with a moving as well as stationary shroud is modeled with a finite-difference method. The numerical results indicate that, within the range of parameters considered, heat transfer characteristics in the cavity are virtually unaffected by the shroud movement. This is in agreement with a previous finding for heat transfer on ungrooved blade tips.