The motion of the target plate is important in some industrial applications which apply multiple jet impingement, such as reflow soldering, drying and food processing. Multiple jet impingement is widely used due to its capacity to generate high heat transfer rates over large and complex areas. This convective process is characterized by several flow interactions essentially due to adjacent jets mixing prior the impingement, wall jets collision after the impingement, as well as crossflow interactions induced by the motion of the wall jets that flow through the exits of the domain. These interactions lead to strong flow recirculation, pressure gradients and boundary layer development. However, the complexity of the flow interactions is increased with the surface motion in confined space, due to the generation of strong shear regions. These interactions can induce problems and product defects due to complicated thermal behavior and non-uniform heating or cooling, being important to fully understand the process in order to reduce time and costs. In that sense, it is of paramount importance to conduct a comprehensive study to analyze and predict the jets flow behavior and the heat transfer over the target plate. To provide an effective contribution in this field, this work addresses the experimental analysis of multiple air jets impinging a moving flat plate. The experiments are conducted on a purpose-built test facility which has been commissioned, using a 2D-PIV system. Through this technique, the flow structure and velocity profiles will be analyzed in detail. The effects of the impinging plate motion on the resulting global and local surface heat transfer are achieved using a thin-film heat flux sensor. Thermocouples will also be placed on the impinging plate in the vicinity of the sensor to measure the surface temperature locally. The multiple jet configuration consists on air flowing through circular nozzles, with a specific diameter (*D*), at ambient temperature and a constant velocity, being the flow characterized by a Reynolds number of 2,000. The air jets impinge on a heated flat plate which moves at a constant velocity. The jet-to-jet spacing (*S/D*) and the jet-to-plate distance (*H/D*) remain constant throughout the experiments. The results are compared for both stationary and moving flat plates cases and express the increased complexity of the flow due to strong interaction between jets and the target surface, which affects the heat transfer performance. The results obtained experimentally are important to clearly define this complex flow and these data can be used in future works for numerical model validation.


Experimental Study of Multiple Air Jets Impinging a Moving Flat Plate

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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