Experimental Study of the Flow and Thermal Development of a Row of Cooling Jets Impinging on a Rotating Concave Surface

Abstract

The paper reports an experimental study of impingement cooling in a rotating passage of semi-cylindrical cross section. Cooling fluid is injected from a row of five jet holes along the centerline of the flat surface of the passage and strikes the concave surface. The cooling passage rotates orthogonally about an axis parallel to that of the jets. Tests have been carried out, using water, both within the passage and as the jet fluid, at a fixed Reynolds number of 15,000, for clockwise and counter-clockwise rotation. Local Nusselt number measurements, using the liquid-crystal technique, show that under stationary conditions a high Nusselt number region develops around each impingement point, with secondary peaks half-way between impingement points. Rotation reduces heat transfer, leads to the disappearance of all secondary peaks and also, surprisingly, of some of the primary peaks. Flow visualization tests suggest that these changes in thermal behavior are caused because rotation increases the spreading rate of the jets. LDA and PIV measurements are also presented. They show that under stationary conditions the five jets exhibit a similar behavior, with their cores remaining intact up to the point of impingement at the top dead center. The LDA and PIV studies help explain the rather surprising thermal behavior under rotating conditions.

Parametric study of turbulent slot-jet impingement heat transfer from concave cylindrical surfaces

“…In order to derive this correlation a functional relationship of the form Nu ¼ CRe m ðD=BÞ n ðh=BÞ p (10) is assumed where, the constant C and the exponents m, n, and p are to be determined through a regression analysis of the 64 predicted data points for the different cases consisting of combinations of the above parameters. The desired functional relationship is obtained as Nu ¼ 0:107Re 0:761 ðD=BÞ À0:346 ðh=BÞ À0:047 (11) The separation parameter (h/B) has a rather weak effect on the average Nusselt number since its exponent is much smaller compared to that of the other parameters. Also the average Nusselt number varies inversely with the surface curvature and spacing (negative exponent) and directly with the Reynolds number (positive exponent).…”

Experiments on impingement heat transfer with film extraction flow on the leading edge of rotating blades

“…However, due to the interaction of the centrifugal, buoyancy, and Coriolis force in the rotation condition, the flow became very complex. Iacovides et al [15,16] studied the flow and thermal characteristics of a row of cooling jets impinging on a rotating concave surface. The local Nusselt number was measured using the thermochromic liquid crystal (TLC) technique.…”

Heat/mass transfer measurement on concave surface in rotating jet impingement

“…Mattern et al [7] reported the local heat/mass transfer distributions on the curved impinging plate with regard to various parameters such as hole-to-hole spacing, hole-to-plate spacing, and jet orientation. Iacovides et al [8] researched the impinging jet under the ultimate rotation condition with Ro = 0.18 and suggested the Nusselt number on the impinging surface. They reported that all secondary peaks and some of the primary peaks in array jets disappear due to strong rotation effect.…”