Abstract

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

Publication Date

1999

Document Type

Thesis

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Kandlikar, Satish

Advisor/Committee Member

Venkataraman, P.

Advisor/Committee Member

Karlekar, B.

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: QC320.3 .M66 1999

Campus

RIT – Main Campus

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