Experimental study of energy conversion on pure water static flashing evaporation considering the gravity

Energy conversion of pure water during the static flash evaporation is analysed with water static pressure taken into consideration.The experiment is conducted by varying the initial temperature and height of water in the range of 50℃ to 80℃ and 3 mm to 60 mm, respectively. The enthalpy difference is the main driving force of the flashing and the superheat can represents the enthalpy difference at the macro level which can be calculated by measuring the temperature of the water. The results indicates that the the gravity has a great effect on the energy conversion during the flashing. According to the evolution of the NEF, the flashing can be divided into rapid evaporation stage(RES) and gradual evaporation stage(GES) and the heat and mass transfer obviously show differences at the two stages. The NEFtp and τtp are introduced as evaluation index to express the completeness of the flashing during the RES and the duration of RES. The initial height of water can increase NEFtp and τtp and the superheat show different effect on the NEFtp. The gravity restrains the growth of the bubbles and extend the the duration of RES. The initial height and superheat positively increase the evaporated mass and mass flow rate during the flashing. It is clear that the gravity can not be ignore when the flashing is studied.