Experimental study of a turbulent impinging jet in an undergraduate heat transfer laboratory

In many industrial applications, a single gas jet or array of jets can impinge upon a surface to enhance heating, cooling or drying effects. This forced convection phenomenon is covered in several heat transfer textbooks in undergraduate engineering courses. An experimental apparatus was developed for students to measure the convection heat transfer coefficient of a single and array of round impinging jets of air upon a resistively heated flat plate. The jet or jet array is directed on one side of the thin plate while the temperature distribution is measured using an infrared camera on the back side. An energy balance allows for estimation of the local and average convection coefficients, presented as non-dimensional Nusselt numbers, which are then compared against correlations in the literature. Experiments with various Reynolds numbers and separation distances between the nozzle and plate are in agreement with correlations, for both a single jet and hexagonal array of 7 jets. This apparatus will be implemented into a laboratory exercise for the heat transfer course at the United States Military Academy.