Proceedings ArticleDOI
Effects of dissolved gases on subcooled flow boiling from small heated regions with and without streamwise concave curvature
P. S. Wu,Terrence W. Simon +1 more
- pp 23-31
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In this paper, the effects of dissolved air in perfluorinated hydrocarbon, FC-72, on flow boiling heat transfer characteristics were experimentally investigated over a range of heat flux from the onset of nucleate boiling (ONB) to the critical heat flux (CHF).Abstract:
Coolants such as fluorocarbon liquids usually contain high levels of dissolved gases. When heated, these gases are liberated from the liquid; if the liquid is boiling, these gases may influence the supply of liquid to the boiling surface. In this study, the effects of dissolved air in perfluorinated hydrocarbon, FC-72, on flow boiling heat transfer characteristics were experimentally investigated over a range of heat flux from the onset of nucleate boiling (ONB) to the critical heat flux (CHF). The experiments were conducted in both straight and curved channels. The boiling surface was a 3 mm/spl times/3 mm patch located on the channel wall. In the curved flow, it was located at the 90/spl deg/ position of a U-bend on the concave wall. Gas content was varied from 1.16/spl times/10/sup -5/ to 2.55/spl times/10/sup -3/ mole/mole, velocity ranged from 0.8 to 6.9 m/s, and pressure was controlled to either 1.41 or 1.92 atm. Subcooling, based on total pressure, was maintained at 27.5/spl deg/C. The data show that reduction of incipience superheat at ONB due to dissolved gases under these forced-convection conditions is much less than with pool boiling or low-velocity flow boiling. Boiling curves for gassy and degassed cases differ at low heat flux levels but merge at higher heat fluxes. The merging may indicate that the near-wall liquid layer is being degassed at higher heat fluxes. Though the high-heat-flux portions of the boiling curves were apparently unaffected by the content of dissolved gas in the approaching liquid stream, the critical heat flux was decreased by as much as 10%. Explanations of this behavior are presented in terms of the two mechanisms for the liquid supply to the macrolayer. >read more
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Proceedings ArticleDOI
Heat transfer from micro-finned and flat surfaces to flow of Fluorinert coolant; boiling heat transfer
TL;DR: In this paper, the authors reported the data of forced convection boiling heat transfer from a 2 cm/spl times/2 cm simulated chip to a fluorocarbon coolant (FX3250) in a parallel-plate channel.
References
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Journal ArticleDOI
Critical heat flux in subcooled flow boiling of fluorocarbon liquid on a simulated electronic chip in a vertical rectangular channel
Issam Mudawar,D.E. Maddox +1 more
TL;DR: In this article, two distinct CHF regimes were established based on flow visualization and experimental data, and experiments were performed to correlate and model CHF during subcooled flow boiling of dielectric fluorocarbon (FC-72) liquid on a smooth 12.7 × 12. 7 mm2 simulated electronic chip inside a vertical rectangular channel.
Heat transfer in nucleate boiling of mixtures
TL;DR: In this paper, an equation for predicting heat transfer coefficients for nucleate boiling of mixtures is derived, which contains only one adjustable parameter and the liquid-phase mass transfer coefficient.
Book ChapterDOI
Transition boiling heat transfer
TL;DR: In this article, the experimental results on the transition boiling mechanism and the estimates of heat-transfer rates were presented, and it was shown that, with transition boiling, at each time instant, the liquid wets some part of the heating surface and the remainder is covered by a vapor film.
Journal ArticleDOI
Effect of dissolved gases on subcooled flow boiling heat transfer
TL;DR: In this paper, the influence of various dissolved gases (He, N 2, Ar, CO 2, C 3 H 8 ) on subcooled boiling heat transfer was investigated for flow of water and of heptane in an annulus with a heated core.