Local heat transfer measurements were taken for the stagnation region of a free surface, axi-symmetric jet of distilled water impinging upon a heated copper surface. The effect of jet velocity (1 .5m/s < Vn < 3.5m/s) and liquid subcooling (20C < (delta)Tsub^ 75C) were studied on both single-phase and nucleate boiling flow regimes. As expected, the single-phase heat transfer coefficient was directly affected by jet velocity, while subcooling produced only minor changes due to temperature dependent fluid properties. The heat flux required for boiling incipience was directly related to both jet velocity and subcooling, with a significant increase noticed in the event of single-phase temperature overshoot. This temperature excursion was noted at high subcoolings (60C < (delta)Tsub^ 75C), and appeared to increase with jet velocity (Vn = 3.5m/s). The fully developed boiling data was independent of both jet velocity and liquid subcooling, and is correlated by the expression q"=70*ATsat30 with a standard deviation of 1 .31 C. The effect of hysteresis was studied by obtaining data for increasing and decreasing heat fluxes at each condition. With a jet velocity of 3.5 m/s, subcooling of 20C, and heat flux of 2.43 MW/m2, the wall superheat was seen to vary in excess of 8.5C depending on direction of the changing heat flux. A single data point was obtained in the CHF regime at the minimum jet velocity (Vn = 1 .5m/s) and liquid subcooling (delta)TSUb = 20C) at a heat flux of 4.48 MW/m2.
Library of Congress Subject Headings
Heat--Transmission--Research; Water jets; Nozzles--Fluid dynamics
Department, Program, or Center
Mechanical Engineering (KGCOE)
Moorhead, Michael, "An Experimental investigation into the effect of nucleate boiling on a free-surface, axi-symmetric jet of water impinging vertically downward upon a heated copper suface" (1999). Thesis. Rochester Institute of Technology. Accessed from
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