Effect of jet hole arrays arrangement on impingement heat transfer

A comprehensive investigation on impingement heat transfer of different jet array arrangements is presented. Experiments on the inline jet arrays and the linearly stretched arrays are performed using transient liquid crystal technique. Three experimented basic inline jet arrays are configurations 4X4, 8X4 and 8X8. Two experimented cases for the linearly stretched arrays are the uniform diameter case and the varying diameter case. For the inline jet arrays, three jet heights Z/D=1, 3 and 5 and three Reynolds numbers Re=5000, 10000 and 15000 are investigated. For linearly stretched arrays, the same three jet heights and Re=2000, 6000 and 10000 are investigated. Detailed local Nusselt number distributions are presented and compared for each case. Spanwise averaged heat transfer coefficients are plotted and compared. Data analysis indicates that for the inline jet arrays, Z/D=3 produces higher heat transfer coefficients and for the linearly stretched array, the varying diameter case produces higher heat transfer coefficient at large Reynolds number. Experimental data is compared with two correlations from Kercher and Tabakoff and from Florscheutz et al. Experimental results are comparable to these two correlations but comparisons also show that both correlations over-estimate the heat transfer coefficient for the first impingement jet row and under-predict the heat transfer coefficient for strong cross-flow situation. Furthermore, they are imprecise for complicated jet array geometries.