Experimental study on concentrating characteristics during static flash of aqueous NaCl solution at different flash speeds

This experimental study explores the concentration characteristics of aqueous NaCl solution in static flash evaporation, focusing on the equilibrium mass and concentration, at different flash speeds ( FS ). An aqueous NaCl solution, with an initial concentration (mass fraction) of 0.15 to 0.26, was employed as the working fluid. The superheat varied from 1.49 K to 54.9 K, while the flash speeds were adjusted from 0.006 s −1 to 0.53 s −1 . The study delineates the flash evaporation process into two regions based on the interplay of heat transfer and steam-carrying effects: one where both factors are co-dominant, and another where heat transfer is the primary controlling element. The results indicate that increasing the flash speed effectively raises the equilibrium concentration in the co-controlled region but has no impact in the region dominated solely by heat transfer. Furthermore, initial saturation conditions at various flash speeds to predict whether the flash evaporation process is occurring in the co-controlled or heat transfer-controlled region are proposed. Calculating method of equilibrium mass/concentration at different flash speeds was set up.