Experimental and Numerical Investigation of Impingement Heat Transfer on Target Plate with Streamlined Roughness Element at Maximum Crossflow Condition

A combined experimental and numerical investigation of the heat transfer and flow characteristics of the roughened target plate has been conducted. All the data are compared with the flat plate. Three novel streamlined roughness elements are proposed: similar round protuberance, similar trapezoidal straight rib, and similar trapezoidal curved rib. The experiments are carried out in a perspex model using the transient thermochromic liquid crystal method. The effect of jet Reynolds number, rib height, and rib shape on the Nusselt number and flow discharge coefficient has been investigated. Higher ribs provide higher heat transfer enhancement. The curved ribs provide better heat transfer performance. Within the experimental scope, combined straight rib plate and combined curved rib plate increase the area averaged Nusselt number by 11.5% and 13.8% respectively. The experiment is complemented by a numerical part, which can provide flow field analysis and the Nusselt number on the surface of the small size roughness element. The numerical results show the protuberance can shorten the nozzle to plate distance and make the shifting point move forward. The ribs have a guidance effect on crossflow and reduce the transverse interference to the downstream jet. The transferred heat flux caused by the side surface of the roughness element is very obvious. The heat flux contributed by the side surface of the protuberance and ribs can reach 26% and 10% respectively.