Membrane process, mass transfer modeling transport

This simple mass transfer model based on simplified film theory has been proposed to describe the process of facilitated transport of penicillin-G across a SLM system [53]. In the authors laboratory, CPC transport using Aliquat-336 as the carrier was studied [56] using microporous hydrophobic polypropylene membrane (Celgard 2400) support and the permeation rate was found to be controlled by diffusion across the membrane. 

The mass transfer of an emulsion liquid membrane process has been modeled mathematically. An analytical solution which allows prediction of concentrations of solutes in the external phase, membrane phase, and external phase-membrane interface was obtained. Experimentally, arsenic was selected as a solute in the external phase to be removed by the ELM process. Our model gives an excellent representation of the experimental data for the external concentration of the arsenic versus time. In addition, the model predicts the concentration distribution in the membrane phase at any time. Thus, the overall distribution of solutes in three phases (external, membrane and internal) at ahy time of the ELM process can be evaluated. From the model, it was found that the ELM process was characterize by two dimensionless groups. One group for the transport phenomena governs the rate of mass transfer or the Biot number. The other group includes the... 

Comprehensive monographs are also available detailing the analysis of mass transfer though porous and dense membranes. Standard textbooks [e.g., Refs. 26, 27] provide the basis for discriminating between various possible transport mechanisms and the selection of models capable of describing the processes in quantitatively. 

Despite this last observation, for this type of simulation and modelling research, two main means of evolution remain the first consists in enlarging the library with new and newly coded models for unit operations or apparatuses (such as the unit processes mentioned above multiphase reactors, membrane processes, etc.) the second is specified by the sophistication of the models developed for the apparatus that characterizes the unit operations. With respect to this second means, we can develop a hierarchy dividing into three levels. The first level corresponds to connectionist models of equilibrium (frequently used in the past). The second level involves the models of transport phenomena with heat and mass transfer kinetics given by approximate solutions. And finally, in the third level, the real transport phenomena the flow, heat and mass transport are correctly described. In... 

The second set of simulations is oriented towards the analysis of the simultaneous heat and mass transfer when two fluids are separated by a porous wall (membrane). The interest here is to couple the species transport through a wall associated with the heat transfer and to consider that the wall heat conduction is higher than the heat transported by the species motion. The process takes place through a cylindrical membrane and we assume the velocity to be quite slow in the inner compartment of the membrane. The process is described schematically in Fig. 3.65. The transformation of the above general model in order to correspond to this new description gives the following set of dimensionless equations ... 

The SGMD is a temperature driven process, and it involves (a) evaporation of water at the hot feed side, (b) transport of water vapor through the pores of hydrophobic membrane, (c) collection of the permeating water vapor into an inert cold sweeping gas, and (d) condensation outside the membrane module. A decrease in driving force has been observed due to polarization effects of both temperature and concentration [80,82]. To calculate both heat and mass transfer through microporous hydrophobic membrane as well as the temperature and concentration polarization layer, the theoretical model suggested by Khayet et al. [58] can be written as... 

Membran systems are known to play an important role in functioning biological objects (in mass transfer processes, passive and active transport of substance, regulation of an endocellular metabolism, in bio-energetics, etc.). Unique properties of biomembranes are caused by their structure, in particular, presence of bimolecular focused layers of lipids. At the same time, one of the main disadvantages of modelling lipid membran systems (monolayers, flat bilayers, liposomes), is their low stability in time and to action of external factors. 

Mathematical modeling and determination of the characteristic parameters to predict the performance of membrane solvent extraction processes has been studied widely in the literature. The analysis of mass transfer in hollow fiber modules has been carried out using two different approaches. The first approach to the modeling of solvent extraction in hollow fiber modules consists of considering the velocity and concentration profiles developed along the hollow fibers by means of the mass conservation equation and the associated boundary conditions for the solute in the inner fluid. The second approach consists of considering that the mass flux of a solute can be related to a mass transfer coefficient that gathers both mass transport properties and hydrodynamic conditions of the systan (fluid flow and hydrodynamic characteristics of the manbrane module). 

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