Study On Mass Transfer Performance And Enhancement Of Hollow Fiber Mambrane Modules

Hollow fiber membrane modules have many advantages such as lightweight, small volume and much bigger surface area per unit volume than othermembrane modules. The study on mass transfer performance of hollow fibermembrane contactor is a priority and hard spot issue. In this paper, the masstransfer characteristics of the hollow fiber membrane modules were simulated invibration and static condition, finally field synergy principle was used to analyze.In this paper, hollow fiber is modeled by random distribution, and Gaussianfunction N(R, sigma) was used to model the polydisperse out radii of hollowfiber. This paper discussed the influence of different sigma on mass transfercoefficient with fiber packing density ranging from0.1to0.4. It was found that,the effect of different sigma on the logarithmic mean Sherwood numberdecreased with increasing fiber packing density. When the packing densityincreased to0.4, the removal of dissolved oxygen could meet the requirementof power industry, no matter how much value the sigma was. With the sigmaincreasing, the deviation of max and min Sherwood number from the averagevalue increased gradually, except when the sigma was0.05. This paperdeduces there is a best value of sigma for membrane modules when the fiberdistribution is randomly distributed.Concentration polarization is a major factor to reduce the mass transferefficiency. In order to improve the performance of hollow fiber modules,dynamic mesh of computational fluid dynamics software FLUENT was used tostudy the characteristics of flow and mass transfer inside vibration tubes to getthe velocity and concentration distribution in a cycle, and the effect of different vibration parameters on mass transfer performance was analyzed. Thenumerical results show that vibration was favorable to mass transferenhancement. And concentration polarization was prevented. The clearancerate gets larger with the vibration frequency and amplitude increase. Butenhanced vibration frequency is much better than increase amplitude to theeffect of mass transfer enhancement.Field synergy principle was used to analyze the performance of masstransfer modules. When the module is vibrating, the cosine of synergy angle ismuch bigger than that without vibration. The cosine of average synergy anglegot larger with the frequency increased. But the rising tendency is slow. Themass transfer performance does not increase linearly with the frequency. Thesynergy number decreased with the Reynolds number increased. Increase thevelocity of fluid can increased the Reynolds number which indicates that thesynergy degree between the velocity field and concentration gradient fieldreduced.