Heat and Mass Transfer between Water Droplet and High Temperature Environment

Water mist is a high efficiency and non-contaminative fire extinguishing agent, and its extinguishing mechanism is not clear completely. From species equation and energy equation of droplet surface, heat and mass transfer and lifetime of droplet in still high temperature environment were discussed. Using converting film theory, it is put forward that heat and mass transfer are achieved by boiling via comparison of characterisitcs time. Taking into accounting the coupling effect of variation of droplet diameter and velocity, heat and mass transfer of droplet within forced convection high temperature environment are studied using numerical method. The results show that it is impossible to carry out fire suppression by flame cooling and surface cooling for smaller droplet. Its extinguishments depend primarily upon decalescence via gasification.