Visualization of Heat Transfer Enhencement Regions Modified by The Interaction of Inclined Impinging Jets into Crossflow
by
Elzbieta Fornalik
University of Mining and Metallurgy, Krakow, Poland
Coauthors: Yu Yamamoto, Wei Chen, Kazuyoshi Nakabe, Kenjiro Suzuki

ABSTRACT

As an effective method to enhance heat and mass transfer, impinging jets have been used in many industrial applications; the drying process of papers and films, the tempering process of glass, the annealing process of steel, the cooling process of gas turbine system and electronic components, etc. Numerous analytical and experimental studies have been made by many researchers to investigate the basic heat transfer characteristics of jet impingement.

    The authors previously focused on the jet orientation to generate large-scale steady vortices and carried out flow and heat transfer experiments for an obliquely discharged jet into crossflow^1-2. In the present study, as the next step, the attention was paid to the visualizations of flow and heat transfer fields modified by the interaction between the two jets obliquely discharged into crossflow, and also to the comparison of the heat transfer performance between vertical and oblique jet cases. The temperature of the heat transfer target surface were measured with thermochromic liquid crystal sheets. The colors of the liquid crystal images taken by a CCD camera were transformed accurately and effectively into the temperatures by means of the neural network technique to obtain Nusselt number distributions on the target surface. Fluorescent dyes were added to the jet fluid to visualize also the cross-sectional flow patterns with the light sheet of a laser.

REFERENCES

    1. Nakabe K., Suzuki K., Inaoka K., Higashio A., Acton J. S. and Chen W.: Generation of Longitudinal Vortices in Internal Flows with an Inclined Impinging Jet and Enhancement of Target Plate Heat Transfer Int. J. Heat and Fluid Flow 19, p.573, 1998.
    2. Nakabe K., Yamamoto Y., Fornalik E., Chen W. and Suzuki K.: Visualizations of Obliquely Discharged Jet Flows and Their Heat Transfer Enhancement Regions CD-Rom Proc. 8th Int'l. Symp. on Flow Visual., ISBN 09533991 0 9, Sorrento 1998.

Date received: February 2, 1999