Experimental study on heat transfer characteristics in static flash evaporation of aqueous NaCl solution

Abstract

An experimental study of heat transfer characteristics in static flash evaporation of aqueous NaCl solution was presented. Experiments were conducted using initial concentration of water film that varied from 0 to 0.26 (saturated at room temperature), initial height of 0.1 to 0.4m, and superheat ranging from 1.8 to 49.5K. Flash evolutions of pure water and aqueous NaCl solution were obtained during static flash evaporation. Influences of crystals on non-equilibrium fraction (NEF) and volumetric heat transfer coefficient were analyzed. Results suggested that the duration of fast evaporation was long, and NEF with crystallization reached a low equilibrium value. Crystallization correction factor φ was introduced to modify fitting formula NEF in the cases where crystallization occurred. A minimum value of volumetric heat transfer coefficient existed with the rise of fm0 because of the crystals. The fm0 that corresponds to the minimum volumetric heat transfer coefficient decreased with the increase of ΔT.