Abstract: Based on the second law of thermodynamics for an open system under non-equilibrium state an intensive analysis of the entropy generation in the process of falling film evaporation was made.A quantitative correlation was deduced to calculate the unit entropy generation number,N_s from the traditional Reynolds number and other parameters under the condition of Re>1450(c_pμ/λ)-1.06(0.5-0.25ω)^-1.It was unveiled that N_s decreased with decreasing thickness of the falling film and increased after the optimal ω, which corresponded with a minimum value of N_s.The good agreement between the expressions of correlation and the results obtained from an experimental rig of falling film evaporation for phosphoric acid concentration in a vertical heated tube with the dimension of φ30×2×6000 demonstrated that the correlation equation could be rationally used to predict the entropy generation in falling film evaporation.This theoretical prediction, calculated from ordinary thermal process parameters is useful in enhancement of thermodynamic efficiency in industrial processes.

Key words: 降膜蒸发, 熵产, 单位熵产数, 最小熵产分析

摘要： 从热力学第二定律出发，将普适体系的熵产表达推广于降膜蒸发过程熵产分析并得到熵产计算式.引入单位熵产数并得到Reynolds数大于1450(c_pμ/λ)^-1.06(0.5-0.25ω)^-1情况下和Reynolds数之间的定量关系，据此揭示了降膜蒸发过程熵产随降膜管内液膜厚度减小先降低再增大的规律，对应存在最小熵产数.与φ30×2×6000传热管内磷酸降膜蒸发实验数据对比结果吻合良好，表明本文熵产计算式可以根据过程的热力参数表达降膜蒸发过程的熵产规律，对过程强化和提高热力学效率具有实际指导意义.

关键词: 降膜蒸发, 熵产, 单位熵产数, 最小熵产分析