Optimization of Single Row Jet Impingement Array by Varying Flow Rates

Abstract

The current detailed experimental study focuses on the optimization of heat transfer performance through jet impingement by varying the coolant flow rate to each individual jet. The test section consists of an array of five jets, which is individually fed and metered separately, and expels air through one exit. The jet diameter D, channel height to jet diameter H/D, and jet spacing to diameter S/D, are all held constant at 9.53 mm (0.375 in), 2 and 4 respectively. The Reynolds number, which is based on jet diameter and bulk mean velocity at each jet, ranges from 50,000 to 80,000. A transient liquid crystal technique is employed in this study to determine the local and overall-average heat transfer coefficient distribution on the target plate. Commercially available CFD software, ANSYS CFX, is used to qualitatively correlate the experimental results and to provide detailed insights of the flow field created by the array of jets. The results revealed higher heat transfer coefficients in the impingement area, while decreasing in the radial direction. The upstream region exhibited high heat transfer performance, which is ultimately driven by the jet impingement from the first jet to the third jet. Heat transfer performance decreases at the downstream region with the development of cross-flow. By varying the jet flow rates at approximately ±2%, local heat transfer at the downstream region is elevated and the total heat transfer enhancement on the target surface is enhanced up to 35% compared to the baseline case.