Temperature traces of water aerosols, water-based emulsions, solutions and slurries moving in a reversed flow of high-temperature gases

Abstract

Over the recent years, a number of studies have been dedicated to heat and mass transfer during the interflow of gases and aerosols. The most important task here is to control the temperature of the forming gas-vapor mixture. The temperature of the latter is difficult to maintain for a long time on a level, required for the application in thermal and flame liquid-cleaning systems, fire extinguishing, or production of power-efficient heat carriers based on flue gases, water vapor, and droplets. Temperature prediction is difficult due to nonlinear dependence of phase transformation rate, which is dominant in extensively heated gas-steam-droplet systems, versus temperature. This work provides experimental study of temperature variation range in typical sections of combustion product flow during aerosol injection. To extend the practical value of the studies for the aforementioned applications – fire extinguishing in the first place – the experiments were conducted with water aerosols as well as water-based solutions, suspensions, and slurries. Initial temperature of combustion product flow was varied in the range of 400–1000 K. Aerosol properties: droplet size 0.01–0.35 mm, droplet volume density (3.8–10.3) · 10−5 m3 of droplets/m3 of gas, initial injection velocity 1–3 m/s, concentration of additives (foam agent, slurry particles, etc.) 0.5–5%. We have established the lifetimes of the aerosol temperature trace. They may differ severalfold depending on the liquid composition used, for instance, water, solutions, slurries, and emulsions. In particular, dependences are presented showing a significant temperature variation in the trace of a droplet aerosol when a small amount (under 1%) of solid or liquid dopants is added. We have derived the approximating equations for all the dependences determined. We have also analyzed several causes of decreases in the temperature of gas-vapor mixture due to heat and mass transfer as well as the predominating phase transformations. Furthermore, we have established the effect of different commonly used additives on forming the sustained temperature trace of water aerosol flow. The experimental distributions of temperatures in the droplet trace and their recovery time serve as a basis for models of heat and mass transfer and phase transformations induced by droplet flows passing through high-temperature gases.