Bubble boiling in droplets of water and lithium bromide water solution

The dynamics of growth and interaction of vapor bubbles in droplets of pure water and LiBr water solution on a horizontal wall were investigated in a wide superheating range. The growth rates of bubbles were determined both in a distillate droplet and in a salt solution droplet. The bubble growth rate in a pure water droplet at the final stage is somewhat lower than in pool boiling. The bubble growth rate in a salt solution is substantially lower than for pure water. Due to the bubble density maldistribution, the vapor flow density is appreciably higher at the droplet edges than on the droplet axis. Collective behavior of the bubbles possesses both stochastic character and elements of self-organization. The thermal measurements were carried out by means of high-speed video and blowup thermal imager.     

Peculiarities of nonisothermal desorption of drops of lithium bromide water solution on a horizontal heated surface

The behavior of a drop of lithium bromide solution on a heating surface is investigated in a wide range of surface temperatures and solution concentration. Substantial peculiarities of evaporation and boiling of single drops in the lithium bromide solution are revealed.     

Boiling crisis in droplets of ethanol water solution on the heating surface

Evaporation of droplets of ethanol water solution on a heated surface is studied experimentally at high heat fluxes. The behavior of water-alcohol mixtures was examined under the conditions of heat transfer crisis. Direct measurement of the current mass of evaporating droplets allows us to study the behavior of liquid batches in significantly nonstationary processes. An insignificant alcohol admixture to water increases significantly the transitional area of the crisis. The maximal length of transitional area corresponds to a mass concentration of alcohol of about 30%. For this concentration the heat transfer coefficient of the water-alcohol solution is maximal. It is shown that addition of highly volatile liquids to water allows efficient control of evaporation rate, which can be used for engineering processes.     

Effect of Diameter of Granules on Dissociation of Methane Hydrate

The kinetics of dissociation of methane hydrate in air at an external pressure of 1 bar was experimentally studied. It is shown that to describe the mechanism of dissociation of gas clathrate, it is necessary to take into account not only the degree of deviation of temperature and pressure from equilibrium values, but also the diameter of granules. As the diameter decreases, the rate of decomposition of methane hydrate increases significantly. Change in the grain size affects formation of pores and dissociation. The experiment demonstrated a self-preservation mechanism for granule diameters of more than 1 mm. In the case of powder with an average diameter of less than 0.3 mm, there was no self-preservation. The rate of dissociation depends on the combined effect of diffusion, crystallization, and creep.