Study and Application of Hemispheric Cavities for Surface Heat Transfer Augmentation

Abstract

Results of experimental study of heat transfer and flow phenomena associated with application of hemispheric cavities to augment convective heat transfer are presented. Study is performed for different geometries and various flow parameters, including turbulence. Experimental correlations for the curved surfaces applicable to gas turbine internal airfoil cooling are obtained and analyzed for both heat transfer and pressure losses. Effectiveness of the augmentation technique, considering a simplicity of fabrication process, is emphasized.

Analysis of numerical results for two-pass trapezoidal channel with different cooling configurations of trailing edge: The effect of dimples

“…However, the dimple size, dimple depth (depth to diameter ratio ¼ 0.1 to 0.3), distribution and shape (cylindrical, hemispherical, teardrop) effect the heat transfer distribution in the channel [6]. Schukin et al [7] studied the effect of channel geometry (constrictor and diffuser channels) on the heat transfer downstream of a single hemispherical dimple with sharp edge. The diameter of the dimple was 0.5 mm and depth to diameter ratio (H/ d) was 0.5.…”

Experimental Study of Heat Transfer and Pressure Loss in Channels with Miniature V Rib-Dimple Hybrid Structure

“…In the cooling channel, the dimples at the wall provide a significant heat transfer enhancement by producing strong vortex flow near the wall [1][2][3][4][5][6]. Afanasyev [1] investigated the heat transfer and flow resistance characteristics of spherical dimples.…”

“…They found that the dimple vortex generators can increase the heat transfer enhancement by increasing turbulence of the flow. Schukin [3] applied the dimples to the turbines cooling, and measured the average heat transfer coefficient. Park, et al [4] used CFD to simulate the internal flow field and the local heat transfer intensity field of the cooling channel with the dimple vortex generator arranged on the wall, and the results show that the dimples produce strong and orderly vortices, and there is a flow re-attachment in the near-wall region.…”

Computations of Flow and Heat Transfer in a Channel With Rows of Hemispherical Cavities

“…These enhancement technique involve extended surfaces that protrude into the cooling passage. In a recent report by Schukin, et al (1995), the potential of using concavities was mentioned. With concavities, the extended surface is indented instead of protruded, which could lead to heat transfer augmentation at markedly reduced drag.…”

“…Though a number of theories have been advanced on the mechanisms by which concavities enhance surface heat transfer (see, e.g., Schukin, et al (1995) and Chyu, et al (1997)), no studies have been reported that describe the flow induced by concavities and how that flow affects surface heat transfer. The objective of this investigation is to perform such a study by using computations that assume steady, three-dimensional flow.…”