The progress of the two-phase flow research has been divided into four stages. These period are 1948-1959, 1960-1970, 1971-1979, and 1980-1990. In this 10th report, the development of researches on the flow instabilities in boiling channels in the second period conducted in European countries and “The Symposium on Two-Phase Flow Dynamics” (EURATOM) held on 1967 have been introduced from the historical aspect. At the end of this period, the problem on the flow instabilities was systemized by Bouré et al.'s review. The classification of flow instability and Aritomi's classification are briefly introduced to explain these many modes of the flow instability.
The recent development on studies of the phase transition from a vapor to liquid phase at the vapor-liquid interface is reviewed. An experimental method by a shock tube makes it possible to determine the condensation coefficient through the measurement of the growth rate of a liquid film formed on the shock tube endwall behind a reflected shock wave. Theoretical basis for the method is given on the basis of the analysis of gas dynamics equations with kinetic boundary conditions. The condensation coefficients of methanol, acetic acid, and carbontetrachloride vapor are determined with good accuracies. Computer simulations of dynamic processes of evaporation and condensation at the interface are also introduced.
In this report the evolution of layering and the mechanism of degradation of layers formed from a stably stratified solution between the heated and cooled vertical parallel plates are precisely discussed. The relationship between Ra, f which expresses the dimensionless parameter of temperature fluctuation in the layer and Ra, w which is related to the intensity of the natural convection flow induced by the heated and cooled walls is obtained. When Ra, w is less than 15000, Ra, f increases with the increase of Ra, w and the flow is laminar. When Ra, w is between 15000 and 25000, Ra, f increases rapidly with the increase of Ra, w and the transition to turbulence occurs. The analysis shows that the temperature fluctuation in the layer is attenuated due to the transfer of heat across the interfaces contacting with upper and lower layers and the horizontal convection flow disappears when the critical value of Ra, w is 16800.
With steam explosions in the reactor pressure vessel now considered to pose an acceptably small risk to the safety of a nuclear light water reactor, steam explosions in the containment vessel are being given considerable attention. In these hypothesized events, molten nuclear fuel is ejected into the containment vessel as a high-temperature jet surrounded by molten particles. The jet undergoes breakup in the coolant pool and, as it mixes with coolant, explosively high evaporation rates may arise. Herein, a jet breakup model for containment vessel scenarios, with the primary breakup mechanism being the Kelvin-Helmholtz instability, is described.The one-dimensional jet breakup model solves mass and energy conservation equations for the vapor film surrounding the jet and for jet fragmentation and returns these results back to the VESUVIUS code for analysis of jet dynamics and the entire steam explosion process. In the companion Part 2 paper, comparisons of VESUVIUS calculation results against experimental data are discussed.
It is indispensable to know detailed behavior of liquid film flow on nuclear fuel rods for the prediction of critical heat flux in boiling water reactor.The authors have developed a new measuring method based on an ultrasonic transmission technique adopting a highly rotating reflector for the measurement of time-dependent two-dimensional liquid film thickness around a tube simulating a nuclear fuel rod. This method has been applied to measure annular dispersed flow.The results showed a promising tendency of the method.