Explosive disintegration of two-component drops under intense conductive, convective, and radiant heating

Abstract

The disintegration of drops of liquids, suspensions, solutions, emulsions, and fuels is one of the most effective ways to enhance heating and evaporation. However, in some cases, the preliminary disintegration of drops for creating a fine dispersed aerosol, i.e. at the entrance to the appropriate heat exchange unit (or combustion chamber), is an ineffective way because of the effects of coagulation, as well as the entrainment and deceleration of the dropwise flow by high-temperature flue gases. As a result, researches are mostly focused on intensification of drops disintegration directly in the heat exchange chamber. Heterogeneous drops are mainly of interest for the fuel technologies and thermal purification of water from irregular impurities. This paper presents the results of experimental studies of heating, evaporation, surface transformation and micro-explosion of two-component drops under different conditions of energy supply. The studies are carried out for drops consisting of liquid combustible (oil product) and non-combustible (water) components. Two-liquid drops are heated on a substrate (conductive heating), in a stream of heated air (convective heating), and in a muffle furnace (radiant heating). The study demonstrates various modes of heating and disintegration (puffing and micro-explosion) of drops, as well as the consequences in terms of the number and size of the formed droplets in the aerosol cloud. The results show that the micro-explosion of drops during the conductive heating requires much lower temperatures compared to radiant and convective heating. The longest warming-up times of drops prior to disintegration are recorded at the radiant heating due to smaller heat fluxes as compared to other heating schemes. At the same time, the relative disintegration coefficient of drops is maximum at the radiant heating. As a result, the maximum evaporation surface area of liquid after the disintegration of the initial two-component drop has been found. We have analyzed the vaporization process of liquid combustible (petroleum) and non-combustible (water) components, as well as products of their oxidation.