A single subcooled jet of water which undergoes boiling upon impingement on a discrete heat source is studied experimentally using time-resolved stereo particle image velocimetry (PIV). The impinging jet issues from a 3.75 mm diameter sharp-edged orifice in a confining orifice plate positioned 4 orifice diam- eters from the target surface. The behavior at jet Reynolds numbers of 5,0 0 0 and 15,0 0 0 is compared for a constant jet inlet subcooling of 10 °C. Fluorescent illumination allows for simultaneous imaging of both the flow tracers and the vapor bubbles in the flow. Flow structure, time-averaged velocities, and turbu- lence statistics are reported for the liquid regions within the confinement gap for a range of heat inputs at both Reynolds numbers, and the effect of the vapor generation on the flow is discussed. Vapor genera- tion from boiling is found to modify the liquid velocities and turbulence fluctuations in the confinement gap . Flow in the confinement gap is dominated by vapor flow, and the vapor bubbles disrupt both the vertical impinging jet and horizontal wall jet flow. Moreover, vapor bubbles are a significant source of turbulence kinetic energy and dissipation, with the bubbly regions above the heated surface experiencing the most intense turbulence modification. Spectral analysis indicates that a Strouhal number of 0.023 is characteristic of the interaction between bubbles and turbulent liquid jets.
Jet impingement, Boiling, Two-phase flow, Turbulence PIV, Fluorescence imaging
Date of this Version
M. J. Rau, T. Guo, P. P. Vlachos, and S. V. Garimella, “Stereo-PIV Measurements of Vapor-Induced Flow Modifications in Confined Jet Impingement Boiling,” International Journal of Multiphase Flow, Vol. 84, pp. 19-33, 2016.