Experimental and numerical simulation study on the mass transfer characteristics of static flash evaporation

Abstract

Due to the short duration and intense nature of static flash evaporation, and limited by the measurement methods, there is still limited understanding of the inhomogeneous characteristics of mass transfer within the waterfilm. This paper studies the spatiotemporal variation of mass transfer characteristics during static flash using experimental and numerical simulation methods. The formation and evolution mechanism of the bubble layer is analyzed, and its impact on the spatial distribution of temperature within the waterfilm is explained. Firstly, it was found that during the flash process, the temperature difference at different heights of the waterfilm first increases and then decreases. Secondly, during the flash process, there is a maximum value of the vapor generation rate within the waterfilm along the height direction of the flash chamber, and there is a spatial inconsistency between the vapor generation rate and the superheat distribution. Thirdly, reducing the initial waterfilm height can improve the consistency between the maximum superheat and the maximum volume fraction, resulting in a higher vapor generation rate per unit mass and an earlier peak appearance. This study contributes to a deeper understanding of flash mass transfer and provides ideas for the future enhancement of flash evaporation.