Publication de 18 numéros par an
ISSN Imprimer: 1064-2285
ISSN En ligne: 2162-6561
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Dynamics of Semi-Infinite and Local Sites of Film Boiling
RÉSUMÉ
The problem of dynamic development of the semi-infinite and local sites of film boiling arising under conditions of unsteady - state heat release is solved by a numerical method. This problem was solved for one - dimensional and two -dimensional film boiling sites. A dimensionless parameter, characterizing the ratio of the width of the temperature front along the heater to the characteristic size of capillary force action, is introduced to provide a physically based assignment of boundary conditions at the front of boiling regime. Minimal heat fluxes, determining the stable conditions of the film boiling site in dependence on its initial size under nonstationary heat release, as well as, temperature profiles along the heat -generating surface and dynamic characteristics of the site development under various densities of heat flux are obtained. An experimental investigation of dynamic change in the boiling regimes of cryogenic liquids is performed. Experimental data on the propagation speed of the boundary between the film and nucleate boiling regimes and equilibrium density of heat flux in nitrogen and helium on cylindrical heat releasing surfaces have been obtained with varying relative pressure in the range of (0.036−0.44). The experimental data and calculated relations are compared for the boundary propagation speed of the film boiling regime obtained within the limits of two - zone and three - zone modes of boiling curve.