INFLUENCE OF EXTINGUISHING LIQUID ABSORPTION COEFFICIENT ON INTENSITY OF BOILING AND EVAPORATION OF HETEROGENEOUS DROPLET IN A FLAME

The numerical model and methodology of experimental researches of heat and mass transfer during the heating, boiling and evaporation of heterogeneous water droplet in a high-temperature area are presented in the work. The results of numerical and experimental researches of evaporation of water droplet with a solid graphite inclusion in a flaming combustion area are introduced. The conditions of an “explosive” vaporization mode realization in a contact zone of solid inclusion and liquid film (temperature of gaseous area is Tf  1050 K and water film thickness is R  0.2·10–3 m) are determined. The main stages of studying process are fixed on video: the droplet heat-up, the beginning of bubble formation of vapor at the interface solid inclusion — liquid, the volume increase of vapor bubble, the droplet fission. The influence of optical water characteristic (absorption coefficient of radiant energy kë ) on the typical period th from the beginning of heterogeneous liquid droplet heating to the realization of an “explosive” vaporization conditions is analyzed. It is shown that for droplets with liquid film size R  0.5·103 m the change of the absorption coefficient of radiant energy in a wide range k = 10–3102 m–1 doesn't influence on th significantly. The application possibility of water unprepared (in the case of optical properties) in a special way (for example from open ponds at forest fire extinguishing) for extinguishing composition is substantiated, provided accounting of the absorption coefficient of the liquid in the process of selecting the characteristic sizes of the generated droplets.