Abstract: Experimental studies on heat transfer characteristics of aqueous NaCl solution in static flash evaporation were carried out, with the mass fraction of aqueous NaCl solution varying between 0 and 0.26, initial height of water film varying between 0.1 to 0.4 m, and superheat varying from 1.5 to 40℃. Results showed that at different stages of flash evaporation the effects of superheat on instantaneous heat transfer coefficient were different. At the early stage, instantaneous heat transfer coefficient decreased with the superheat. At the beginning of the late stage, instantaneous heat transfer coefficient increased with the superheat. At the end of flash evaporation instantaneous heat transfer coefficient was nearly irrelevant to superheat. Results showed that the maximum instantaneous heat transfer coefficient value decreased with the increases of the initial height and initial concentration of water film. A fitting formula for instantaneous heat transfer coefficient of NaCl solution was proposed, and it was in good agreement with experimental results in the experimental range. The boiling states were significantly affected by the transient heat transfer coefficient in static flash evaporation.

Key words: static flash evaporation, heat transfer coefficient, non-equilibrium fraction, boiling states