Modeling and data analysis of multistory flat plate quasi-counter-flow membrane dehumidifier

A two-dimensional steady-state heat and mass transfer mathematical model is established to study the performances of air-to-liquid dehumidifier with PVDF ultrafiltration membrane in liquid desiccant dehumidification in this paper. Terms in this mathematical model are amended with experimental data and improved with the method of calculating enthalpy of lithium chloride solution. The mean Nusselt number in air channel and mean Sherwood number are calculated and the correlations are fitted with the relevant quantities for predicting the heat and mass transfer coefficients. Furthermore, the corresponding heat and mass transfer coefficients are obtained and substituted as initial conditions into the mathematical model. Meanwhile, according to the relationship between the moisture content difference and water vapor partial pressure difference between inlet and outlet on air side, the diffusion coefficient is modified to meet the actual situation of the experiment. Joint surface renewal rate is proposed and regarded as a comprehensive index describing the relative motion of the fluids on both sides in the membrane dehumidification process. After analyzing the influences of controlled variables on mass transfer coefficient divided by density, the conclusion is obtained that the variable solution temperature group is inferior to the variable solution concentration group. The importance of maintaining low solution temperature during the dehumidification process is emphasized.