Dry patch formation in diabatic annular two-phase flows
Abstract
Conditions for the formation of a stable dry patch in vertical annular two-phase flows in heated channels are investigated. An analytical model of the force balance for the leading edge of the liquid film is developed. In addition to surface tension, evaporation thrust and capillary forces, the model includes the effect of turbulence, the pressure gradient and the interfacial shear stress. Numerical evaluations are performed to validate the model and to indicate the importance of various factors on the dry patch stability and on the resulting minimum wetting rate of the liquid film. The analyses indicate that good agreement with measurements is obtained in case of stagnant patch formed on liquid film flowing down a vertical surface. It is shown that for low and moderate mass flow rate of the gas phase in vertical co-current annular flow, the force balance is dominated by the stagnation and the shear stress forces. With growing mass flow rate of the gas phase, the pressure gradient and the interfacial shear stress are increasingly important. As a result, in accordance with measurements, the predicted minimum flow rate of the liquid film at which the patch is re-wetted decreases.References
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[2] Adamsson C., Anglart H.: Influence of axial power distribution on dryout: Film flow models and experiments. Nucl. Eng. Des. 240, 2010, pp. 1495-1505.
[3] Ueda T., Isayama Y.: Critical heat flux and exit film flow rate in a flow boiling system. Int. J. Heat Mass Transfer 24(7), 1981, pp. 1267-1276.
[4] Fukano T., Mori S., Nakagawa T.: Fluctuation characteristics of heating surface temperature near an obstacle in transient boiling two-phase flow in a vertical annular channel. Nucl. Eng. Des. 219, 2003, pp. 47-60.
[5] Hobler T.: Minimum surface wetting. Chemia Stosowana 2B, 1964, pp. 145-159.
[6] Bankoff S.G.: Minimum thickness of a draining liquid film. Int. J. Heat Mass Transfer 14, 1971, pp. 2143-2146.
[7] Mikielewicz J., Moszynski J.R.: Minimum thickness of a liquid film flowing down a solid surface. Int. J. Heat Mass Transfer 19, 1976, pp. 771-776.
[8] Doniec A.: Laminar flow of a liquid rivulet down a vertical solid surface. Can. J. Chem. Eng. 69, 1991, pp. 198-202.
[9] El-Genk M.S., Saber H.H.: Minimum thickness of a flowing down liquid film on a vertical surface. Int. J. Heat Mass Transfer 44, 2001, pp. 2809-2825.
[10] Mikielewicz J., Mikielewicz D., Gumkowski S.: A model of liquid film breakdown formed due to the impingement of a two-phase jet on a horizontal surface. Int. J. Heat Mass Transfer 53, 2010, pp. 5456-5464.
[11] Hewitt G.F., Lacey P.M.C.: The breakdown of the liquid film in annular two-phase flow. Int. J. Heat Mass Transfer 8, 1965, pp. 781-791.
[12] Hartely D.E., Murgatroyd W.: Criteria for the break-up of thin liquid layers flowing isothermally over solid surface. Int. J. Heat Mass Transfer 7, 1964, pp. 1003-1015.
[13] Zuber N., Staub F.W.: Stability of dry patches forming in liquid films flowing over heated surfaces. Int. J. Heat Mass Transfer 9, 1966, pp. 897-905.
[14] McPherson G.D.: Axial stability of the dry patch formed in dryout of a two-phase annular flow. Int. J. Heat Mass Transfer 13, 1970, 1133-1152.
[15] Blanghetti F., Shlunder E.U.: Local heat transfer coefficients on condensation in vertical tubes. Proc. 6th Int. Heat Transfer Conference, 2, 1978, pp. 437-442.
[16] Ponter B., Davies G.A., Beaton W., Ross T.K.: The measurement of contact angles under conditions of heat transfer when a liquid film breaks on a vertical surface. Int. J. Heat Mass Transfer 10, 1967, pp. 1633-1636.
[17] Ponter B., Davies G.A., Ross T.K., Thornley P.G.: The influence of mass transfer on liquid film breakdown. Int. J. Heat Mass Transfer 10, 1967, pp. 349-359.
Published
2015-02-07
How to Cite
ANGLART, Henryk.
Dry patch formation in diabatic annular two-phase flows.
Journal of Power Technologies, [S.l.], v. 94, n. 5, p. 85--95, feb. 2015.
ISSN 2083-4195.
Available at: <https://papers.itc.pw.edu.pl/index.php/JPT/article/view/588>. Date accessed: 22 dec. 2024.
Section
Nuclear Power
Keywords
Dryout; Annular flow; Minimum Wetting Rate; Liquid Film
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