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

Abstract

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.

Qualitative assessment of RANS models for Hypervapotron flow and heat transfer

“…The k-epsilon model, however, uses wall functions to bridge the near wall laminar sublayer and fails to predict flow separation or reattachment at any point within the cavity with the result that it incorrectly predicts a single cavity vortex. For a more quantitative comparison, Metzger et al [9] performed heat transfer measurements along the bottom of a cavity where the aspect ratio was varied from 0.1 to 0.5. Since flow patterns were not available, the predicted variation of Nusselt number (non-dimensional HTC) along the bottom of the cavity was compared with experiment (in this case Nu = Ch/k, where C = channel depth above the cavity (5.08 mm), h = local heat transfer coefficient and k = thermal conductivity of the fluid).…”

“…Having established the required boundary layer resolution for predicting the vortex patterns within cavities such as these, various turbulence models were examined and compared to experiment [8,9] to check the accuracy of the solutions. Unfortunately, flow visualisation or heat transfer data for cavities with identical aspect ratios was not available.…”

Computational modelling of the HyperVapotron cooling technique

“…As part of this validation exercise, experiments by Metzger et al [43] were examined, where heat transfer measurements were made along the bottom of a cavity with aspect ratio varying from 0.1 to 0.5. The results for the cavity with D/W = 0.2 are shown in Figs.…”

Numerical investigations on the steady and unsteady leakage flow and heat transfer characteristics of rotor blade squealer tip

“…Metzger et al [2] studied the local convection heat transfer in a narrow slot-type channel with a rectangular groove. The flow was reduced by increasing the groove depth up to an aspect ratio of 0.2 in their experimental measurements.…”