Study on temperature and phase change of water droplet in the process of flash under low pressure

Within the range of low ambient pressures from 200 to 800 Pa, the experiments have been performed to investigate the relation between the ambient pressure and temperature change in the process of the flash of water droplets. Experimental results show that the possibility of bubble created is enhanced since the superheat inside the water droplet is increased with the ambient pressure falls. The rates of bubble growth and water droplet burst are affected by the ambient pressure. The temperature leap is affected by the deviation between the droplet center and the thermocouple, and the temperature leap is great in the center of water droplet. Therefore, the process of the flash is in thermodynamic nonequilibrium condition. Because of the influence of evaporation of water droplet and existence of evaporation wave in the process of flash, there exists minute pressure around the water droplet, even if in the vacuum.