Study of mixed convection characteristics of confined planar jet impingement using the direct temperature gradient interferometric method

•Direct temperature gradient interferometry was used to measure heat transfer rate in mixed convection flow regime.•Geometric variables could considerably affect the heat transfer rate at low Reynolds numbers.•The thermal field around the impingement point became more symmetric by increasing the Reynolds number.•Two distinct zones (i.e. retarded and accelerated) were visualized in the vicinity of the impingement point.•Numerical simulation results were shown to compare favorably with the experimental data.

Experimental and numerical studies were performed to investigate the thermal field of a confined low-speed jet impinging on a hot plate. The slot jet plane and the target heated plate were vertically installed parallel and close to each other. Jet velocity magnitude was limited to the range in which the interaction with the buoyancy driven flow near the heated wall was significant. Experiments were conducted for relatively low Reynolds numbers based on the nozzle hydraulic diameter. Mach–Zehnder Interferometry method was used to study and visualize the thermal field and to determine the variation of local heat transfer coefficient of the hot plate. Interferogram analysis and data reduction procedure were performed by Direct Temperature Gradient (DTG) and Infinite-Fringe (IF) methods. The effects of impingement location with respect to the leading edge of the target as well as the slot-to-plate spacing ratio were studied. Numerical simulation was also performed using a second order finite volume scheme. The ANSYS-FLUENT solver was used for the numerical studies. Results were shown to compare favorably with the experimental data.