Numerical investigation of heat transfer and flow characteristics of a double-wall cooling structure: Reverse circular jet impingement

Abstract

Abstract Double-wall cooling structures are commonly used to enhance the heat transfer in combustor liner and aerofoil internal cooling within gas turbine engines and other industrial applications. This is the first study to adopt a novel reverse jet impingement technique into a double-wall cooling structure in order to achieve a higher heat transfer rate with relatively lower pressure drop. This paper uses the computational fluid dynamics to study crossflow, nozzle configuration, inlet orientation, and jet-to-target spacing distance effects on the heat transfer rate and the discharge coefficient. In this study, jet-to-target spacing was varied from 1.6 to 7 jet diameter, jet-to-jet spacing was 3.4 jet diameter, the reverse tube diameter was 3.2 jet diameter, and jet Reynolds number was set at 23,000. Procedural optimisation throughout the study initially evaluated that nozzles extended through the crossflow channel are more effective than the square-edged nozzles in eliminating the crossflow effect and promoting higher heat transfer. Variation of inlet condition yielded no significant optimisation was found. Jet-to-target spacing was optimised at jet-to-target spacing around 3 jet diameter. The most significant variable affecting nozzle discharge coefficient was the flow area of the outlet. The reverse jet impingement design showed capacity to enhance heat transfer by increasing the internal surface area, and minimise negative crossflow effects, without excessive reduction in the discharge coefficient.