A theoretical study on the evaporation characteristics of falling liquid oxygen films

This paper presents a theoretical model of flow and heat transfer for the falling laminar liquid oxygen film undergoing evaporation for developing falling film type reboilers/condensers applied in air separation units. The model takes into account the effect of the interfacial shear on the film evaporation. The model is solved with an iteration method, and the thickness of the film as well as the heat transfer coefficient is obtained under given conditions. The effects of the inlet Reynolds number, flow length and interfacial shear on the film thickness and the heat transfer coefficient are analyzed in detail. In addition, the variations of the velocities of the vapor and falling liquid film and the interfacial shear with the flow length are also discussed. The investigation results show that with increasing the inlet Reynolds number, the film thickness increases and the heat transfer coefficient decreases. With increasing the flow length, the film thickness decreases and the heat transfer coefficient increases as the liquid film is evaporated. Moreover, the cocurrent interfacial shear has a significant effect on the flow and heat transfer of the falling film by reducing the film thickness and enhancing the evaporation heat transfer.