Heat and mass transfer simulation of gas-liquid two-phase flow in a distillation column based on OpenFOAM
For multiphase mass transfer processes in distillation columns,computational fluid dynamics can be used not only to simulate the flow phenomena,but also to study the heat and mass transfer processes and their interactions with the flow.Based on previous work on gas-liquid flow simulation in distillation trays,this work applied the multiphase flow solver of the OpenFOAM platform.The energy and species transport equations were considered to construct the heat and mass transfer models for the distillation system.The ideal system of cyclohexane-n-heptane and the non-ideal system of ethanol-water distillation were simulated respectively.The distribution of the gas-liquid two-phase flow,component and temperature on the column trays were analyzed.For the ideal system,the ideal solution mass transfer model can provide accurate predictions for the temperature and concentration fields on the trays.However,for non-ideal systems,it was necessary to introduce the activity coefficient model on the basis of the ideal model.To this end,the effects of two activity coefficient models,UNIQUAC and NRTL,were introduced and compared.In the current simulation framework,the activity coefficient models were able to improve the simulation accuracy of temperature and concentration field.The overall trends predicted by the two models were generally consistent with the results in the literature,and the UNIQUAC model agreed better with the literature.In addition,the comparative analysis of gas-liquid two-phase flow field and concentration field distribution showed that the circulating flow of liquid phase can enhance the local mass transfer efficiency of the column tray,resulting in higher efficiency at the liquid inlet and the weir than the tray center.However,the gas-liquid renewal in the circulating region renewed promptly,which led to a reduction in the overall mass transfer efficiency of the column tray.This study can be used for the design and optimization of distillation columns,and it is also valuable for simulations of heat and mass transfer in other gas-liquid two-phase flow systems.
gas-liquid two-phase flowdistillationhot state simulationheat and mass transferOpenFOAM
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