Experimental Analysis of Heat Transfer and Multi Objective Optimization of Swirling Jet Impingement on a Flat Surface

The influence of swirling flow on distribution of wall heat transfer on a flat plate with helicoid swirl inserts is experimentally studied. The focus of the study is on the swirling effect imposed by helicoid surfaces. Six helicoid swirl inserts of single vane, double vanes and triple vanes with swirl number (Sw) of 0.75 and 1.1 are used in this study. The heat transfer measurements are made for the Reynolds number range of 12700 - 32700 and for the nozzle exit to impinging plate distance (H/D) of 1, 2, 3 and 4 using thermo chromic liquid crystal technique. The swirling impinging jet is also compared with circular impinging jet on the heat transfer performance. The obtained experimental results provide the information on the behavior of single, double and triple helicoid swirl inserts on the heat transfer performance. The experimental values are analyzed with multi objective optimization technique of principle component analysis by computing multi response performance index (MRPI). Their performance is presented in terms of heat transfer rate through evaluation of Nusselt number on the impinging surface and heat transfer uniformity and decay of Nusselt number. The principle component analysis reveals that the double helicoid with higher H/D ratio improves performance of the swirling jet with relatively higher computed MRPI. It is found from the analysis of variance (ANOVA) that the H/D ratio contributes significant effect on the output followed by number of helicoid vanes and swirl number.