Comparative study on heat and mass transfer properties of static/circulatory flash evaporation, i.e., non-equilibrium fraction (NEF), evaporated mass and heat transfer coefficient, was presented based on two experimental systems. NEF evolution in static flash was newly fitted by error function equation, based on which a unified calculating model for heat and mass transfer properties of both flashes was set up initially. At last, heat transfer coefficient was redefined as average heat flux released from unit volume of waterfilm under unit superheat. Results suggested that this coefficient was a time-depended function and a peak value existed in its evolution versus time. (C) 2010 Elsevier Ltd. All rights reserved.