Thermal performance of elliptical pins on a semicircular concave surface in the staggered array jet impingement cooling

Abstract

In a jet impingement cooling, decreasing heat transfer on the last jet's region due to the strong crossflow significantly increases thermal stress on the material. Thus, the main objectives of this study are to achieve relatively more uniform heat transfer distribution and enhance heat transfer on the surface compared to conventional jet impingement cooling (CJIC) configuration by mounting elliptical pins on the impingement regions. From this point of view, we have investigated the thermal performance of elliptical pins mounted on the impingement region of a staggered array jet impingement cooling (SJIC) on the semicircular concave surface. Numerical analyses were performed under various Reynolds numbers (Re = 5000, 15000, and 25000), jet nozzleto-target surface spacing (0.5 & LE; G/d & LE; 8.0), and dimensionless orifice plate-target surface gaps (H/d = 4.0 and 8.0). Average Nusselt (Nu) numbers, local Nu contours, flow properties, and Thermal Performance Factor (TPF) on pinned and smooth target surfaces were studied in detail. Results showed that the local and area-averaged Nu numbers increased with reducing G/d and roughening of the surface with elliptical pins compared to conventional SJIC. Maximum heat transfer enhancement was obtained as 55.68% at H/d = 8.0 with extended jets (G/d = 0.5) and elliptical pin roughening surface design. Besides, the highest TPF on the pinned surface is achieved as 1.10 by G/d = 2.0 and H/d = 8.0 at Re = 25000. Furthermore, mounting elliptical pins on the surface provided more uniform heat transfer distribution on the surface compared to flat surface by means of significantly enhancing heat transfer on the last jet region.