Experimental and numerical study on heat transfer characteristics of various geometrical arrangement of impinging jet arrays

In present work, the effects of jet Reynolds number and geometrical parameters including non-identical jet-to-jet spacings, nozzle-to-plate spacing and non-identical slot widths on the local Nusselt number distribution are investigated for quadruple slot jet arrays. Experiments are conducted for Reynolds number ranging from 144 to 505 based on jet hydraulic diameter (Dh), jet-to-target plate distance from 2.3Dh to 3.1Dh, jet-to-jet spacing in the range of 0.1Dh to 0.8Dh, and slot width of 0.2Dh to 0.8Dh at a constant wall temperature (70 °C). Local Nusselt number corresponding to the impingement region, relative minimum and stagnation point increase for any configuration when the Reynolds number is increased and plate spacing-to-jet hydraulic diameter ratio is decreased. The differences between the values of stagnation and maximum Nusselt number are strong function of Reynolds number and geometrical variables. Moreover, more uniform Nusselt number distributions over an isothermal target plate are seen for the cases of w2/Dh > w1/Dh. In addition, the isothermal curves' concentration at the stagnation region decreases when the Reynolds number is increased for the cases of w2/Dh < w1/Dh. The stagnation Nusselt numbers decreases at a constant Reynolds number by increasing jet-to-jet spacing. Furthermore, correlations are derived for the average and stagnation Nusselt number based on experimental data. Mach-Zehnder interferometer, non-contact and non-intrusive method, is used to calculate local heat transfer from visualized undisturbed temperature fields of infinite fringe interferograms with the high accuracy. Finite volume based code is employed for numerical analysis; good agreement between numerical analysis and experimental results is observed.