Development of device to study evaporation behavior of micro-droplets at high temperatures.

Abstract

Leidenfrost phenomenon is one of the unique behaviors of droplets. In Leidenfrost phenomenon, liquid closing to a surface that is significantly hotter than the liquid's boiling point, produces an insulating vapor layer that keeps the liquid from boiling rapidly. This non-contact state between the droplet and the hot surface leads to the decrease in heat transfer and the increase in evaporation time. This phenomenon occurs for the micro-order droplets. For example, it is influence the combustion efficiency of the engine in which fuel sprayed. For another example, the mist CVD, which is one of the functional thin film fabrication methods, also makes a good use of the Leidenfrost phenomenon to make high quality thin films. This has been indirectly proven by the previous experiments, but there was no direct observation, which needs to be verified. In recent years, the evaporation behavior of microdroplets is also involved in the removal of bacteria from the air due to the spread of infectious diseases. In this study, we developed an observation device for checking the evaporation behavior of micro droplets and a program for measuring the droplet diameter, analyzed the evaporation behavior of droplets by optical observation. The experimental results shown that the range of observation conditions was improved and the accuracy of droplet measurement was enhanced. In the future, we will continue to enhance the accuracy of machine and study the observation methods to further improve the measurement accuracy.