Vapour-liquid rebalancing behaviour of free water evaporation kinetics: experimental investigation and modelling

Drying and moisture evaporation are inextricably linked and major attention is focused on thermal conditions. But the non-thermal factors, especially the relative humidity and air distribution of wet air, also affects drying kinetics. Aiming to obtain the drying kinetic features of water evaporation under isothermal conditions, an experimental investigation was conducted using a variation of each single variable method. The experimental phenomena of non-thermal factors affecting evaporation kinetics under different isothermal process were presented. The results show that water evaporation rate is linear with vapor partial pressure difference under constant temperature condition, and nonlinear change in evaporation rate is caused by wet air flow hindering factors, i.e. the wall height above water surface. A vapour-liquid rebalancing behaviour hypothesis was concluded basing on the results, that water is dried by turning into saturated vapour then being transferred through convection and diffusion. The stronger capability to remove saturated water vapor from the liquid surface is associated with higher evaporation rate. A comprehensive evaporation kinetic model was obtained basing on experimental data and the prediction accuracy is verified by an out of sample experiment. The most probable physical reasons behind the thermal condition change caused parameter change rules were interpreted. This proposed vapor-liquid rebalancing hypothesis shows a consistent behavior with respect to drying theory.