Experimental investigation of impinging jet array heat transfer from a surface with V-shaped and convergent-divergent ribs

Abstract

Detailed heat transfer measurements over a surface with V-shaped ribs (V-SR) and convergent-divergent shaped ribs (CD-SR) by a circular impinging jet array was investigated using thermal infrared camera. Both V-SR and CD-SR configurations with an angle of 45°are considered. In-line jet arrays with different exit flow orientations were also considered. The range of parameters for the analysis has been decided on the basis of practical considerations of the system and operating conditions. The effects of different rib heights on the impinging heat transfer along the wall are studied. Five different ribbed surfaces with different rib height and shapes were selected. The rib pitch (p) to rib height (e) ratio is 6. During the experiments, the Reynolds number was varied from 2000 to 10,000, the jet diameter-to-rib height ratio from 0.6 to 1.2, and jet-to-plate spacing from 2 to 12. The heat transfer results of the rib-roughened plate are compared with those of a smooth plate. The heat transfer from the rib-roughened wall may be enhanced or retarded. Best heat transfer performance was obtained with the V-SR arrangements. The presence of rib turbulators on the target plate produces higher heat transfer coefficients than the smooth plate. The average Nusselt number values for the V-SR plate showed an increase ranging from 4% to 26.6% over those for the smooth plate. Correlations have been developed for the average Nusselt number for the rib-roughened surfaces.