In present paper, a series of experiments on circulatory flash evaporation of 15% aqueous NaCl solution was carried out under various main experimental parameters. Circulatory flash speed, which represented the superheated energy consumed in unit time in flash chamber, was defined as average change rate of the non equilibrium fraction during the residence time in flash chamber. It indicated the intensity of flash evaporation. The experiment results showed that circulatory flash speed quickly decreased to a lowest point, then increased monotonously with the increasing superheat and finally became flat. Influence of parameters, such as flow rate, initial height of water film and equilibrium pressure on circulatory flash speed was also investigated. As circulatory flash speed increased, NEF had a minimum value. At the same circulatory flash speed, NEF decreased when superheat degree and equilibrium pressure increased. And comparative study on flash speed between static and circulatory flash evaporation was also conducted. Both theoretical and experimental results of volumetric heat transfer coefficient showed a linear relationship with circulatory flash speed. However, the experimental values were greater than the calculated values due to the liquid droplets entrainment (C) 2016 Elsevier B.V. All rights reserved.