Abstract:

For a liquid droplet in high temperature surroundings of airflow convection and thermal radiation, the heat and mass transfer model of heating and evaporation has been established. The homogeneous boiling criterion was combined with the evaporation model to predict the inside boiling effect of droplet. A computer code was developed to solve the combined governing equations numerically. After verifying, the temperature rising and evaporating process of an n-dodecane droplet were simulated, in which the thermal expansion and property dependence on temperature were considered. The occurrence of boiling inside droplet is investigated for various high temperature conditions of convection and thermal radiation. The results show that the heating of high temperature convection and thermal radiation can both rapidly rise the temperature of droplet and the evaporation is accompanied by an obvious size expansion. Different from the convection heating, however, the thermal radiation can result in more rapidly rising of temperature inside the droplet. When the radiative temperature is high enough and the temperature of convective airflow is lower, the boiling will take place inside the droplet whose radius is not very small. It is also found that the droplet superheat need for boiling increases with the evaporating process.

Key words: liquid droplet, evaporation, high temperature, thermal radiation, boiling