Authors & Affiliations
Zeigarnik Yu.A., Ivochkin Yu.P., Kubrikov K.G., Teplyakov I.O.
Joint Institute for High Temperatures of the Russian Academy of Sciences, Moscow, Russia
Zeigarnik Yu.A. – Chief Researcher, Dr. Sci. (Tech.), Joint Institute for High Temperatures of the Russian Academy of Sciences.
Kubrikov K.G. – Junior Researcher, Joint Institute for High Temperatures of the Russian Academy of Sciences.
Teplyakov I.O. – Senior Researcher, Cand. Sci. (Tech.), Joint Institute for High Temperatures of the Russian Academy of Sciences.
The results of an experimental study of the processes preceding and accompanying the destruction of the vapor films of a cooler (water not warmed to the boiling point) near hot solid and liquid metal samples with a spherical surface are presented. The main models of fragmentation of liquid metal droplets, based on thermal stresses, shock-acoustic effects and explosive boiling of water inside the melt, were analyzed. The results of experiments with liquid metal droplets immersed in the water not warmed to the boiling point are presented. The obtained photographic material testifies to the variety of fragments that are formed during the crushing process. This circumstance confirms the assumption of the existence of various fragmentation mechanisms, which are substantially dependent on the tem-perature of the melt. It was found that when a steel droplet is heated in air, intense sparking (drop erosion) of the metal is observed, which obstructs the formation of film cooler boiling regime and helps to prevent explosive fragmentation of the melt. It is shown that the cooling rates of heated steel metal balls and melts of their drops differ significantly from each other (it is several times higher for liquid metal drops). Experiments with solid metal samples in which the process of contacting water at room temperature with a hot surface (170—620°C) was studied using the conductometric method are described. The results of measurements of pulsations of electric current, the magnitude of which is proportional to the area of electrical contact are presented. The measurements were carried out in the modes of film, transitional and nucleate boiling; the amplitude-frequency characteristics of the obtained oscillograms were investigated using wavelet analysis. It has been established that a short (several milliseconds) process, characterized by an intense generation of electric current pulsations, which can be interpreted as the generation of intense oscillations and waves at the vapor-liquid interface, precedes the boiling up of a cooler on a hot surface. The possible physical nature of such waves contributing to the accelerated local cooling of the heated surface and its direct contact with the cooler is discussed.
steam explosion, liquid metal, low-boiling cooler, fragmentation, boiling, vapor film, cooling rate, hydrodynamic waves, electrical contact, wavelet analysis
1. Corradini M.L., Kim B.J., Oh M. D. Vapor explosions in light water reactors: a review of theory and modeling. Progress in Nuclear Energy, 1988, vol. 22, pp. 1.
2. Berthoud G. Vapor explosions. Annual Review of Fluid Mechanics, 2000, vol. 32, pp. 573.
3. Dombrovsky L.A. Approximate model for break-up of solidifying melt particles due to thermal stresses in surface crust layer. International Journal of Heat and Mass Transfer, 2009, vol. 52, pp. 582.
4. Kazimi M.S., Autruffe M.I. On the mechanism for hydrodinamic fragmentation. Transactions of the American Nuclear Society, 1978, vol. 27, pp. 32.
5. Ivochkin Yu.P., Vavilov S.N., Zeigarnik Yu.A., Kubrikov K.G. K voprosu ob otsutstvii fragmentatsii goryachikh kapel' pri malykh nedogrevakh okhladitelya [About lack of fragmentation for hot droplets at low subcooling of coolant]. Teplofizika i aeromekhanika - Thermophysics and aeromechanics, 2012, no. 19, pp. 429.
6. Grigor'ev V.S., Zhilin V.G., Zeigarnik Yu.A., Ivochkin Yu.P., Glazkov V.V., Sinkevich O.A. The behavior of a vapor film on a highly superheated surface immersed in subcooled water. Teplofizika vysokikh temperatur - High Temperature, 2005, vol. 43, no. 1, pp. 103.
7. Glazkov V.V., Sinkevich O.A., Kireeva A.N. Model of Intensive InterPhase Interaction between High Temperature Melt and Cold Volatile Fluid. Teplofizika vysokikh temperatur - High Temperature, 2014, vol. 52, pp. 210.
8. Zhilin V.G., Zeigarnik Y.A., Ivochkin Y.P., Oksman A.A., Belov K.I. An experimental investigation of the characteristics of explosive boiling of subcooled water on a hot surface under conditions of change of boiling modes. Teplofizika vysokikh temperatur - High Temperature, 2009, vol. 47, pp. 856.
9. Nelson L.S., Duda P.M. Steam explosions experiments with single drops of iron oxide melted with CO2 — laser. High Temperature — High Pressure, 1982, vol. 14, pp. 259—281.
10. Sinkevich O.A. Waves on the surface of a boiling liquid at various medium stratifications. Zhurnal Eksperimental'noy i Teoreticheskoy Fiziki - Journal of Experimental and Theoretical Physics, 2015, vol. 121, no. 2, pp. 321.