Gradient Clogging in Depth Filtration

We investigate clogging in depth filtration, in which a dirty fluid is ``cleaned'' by the trapping of dirt particles within the pore space during flow through a porous medium. This leads to a gradient percolation process which exhibits a power law distribution for the density of trapped particles at downstream distance x from the input. To achieve a non-pathological clogging (percolation) threshold, the system length L should scale no faster than a power of ln w, where w is the width. Non-trivial behavior for the permeability arises only in this extreme anisotropic geometry.Comment: 4 pages, 3 figures, RevTe

Monte Carlo simulation and experimental heat and mass transfer in direct contact membrane distillation

A Monte Carlo (MC) simulation model is developed to study heat and mass transfer through hydrophobic membranes applying direct contact membrane distillation (DCMD) process. In this study, the membrane pore space is described by a three-dimensional network model of inter-connected cylindrical pores with distributive pore size. Vapor flux through membrane pores is described by gas transport mechanism(s) based on the kinetic theory of gases. The present MC model can take into consideration the influence of temperature polarization phenomenon, membrane physical properties including pores interconnectivity and the DCMD fluid dynamic conditions. The developed model can simultaneously predict the DCMD process vapor flux and membrane surface temperatures, contrary to other models in which one of them has to be given in order to solve the other. The model is comprehensive in its approach and does not involve any adjustable parameter. The simulated results were compared with the experimental ones of different membranes and the comparisons were found to be in excellent qualitative and quantitative agreement

Stochastic Model for Filtration of Particulate Suspensions with Incomplete Pore Plugging

The original publication can be found at www.springerlink.comA population balance model for particulate suspension transport with capture of particles by porous medium accounting for complete and incomplete plugging of pores by retained particles is derived. The model accounts for pore space accessibility, due to restriction on finite size particle movement through the overall pore space, and for particle flux reduction, due to transport of particles by the fraction of the overall flux. The novel feature of the model is the residual pore conductivity after the particle retention in the pore and the possibility of one pore to capture several particles. A closed system of governing stochastic equations determines the evolution of size distributions for suspended particles and pores. Its averaging results in the closed system of hydrodynamic equations accounting for permeability and porosity reduction due to plugging. The problem of deep bed filtration of a single particle size suspension through a single pore size medium where a pore can be completely plugged by two particles allows for an exact analytical solution. The phenomenological deep bed filtration model follows from the analytical solution.Shapiro A.A., Bedrikovetski P.G., Santos A., Medvedev O.O