No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Filtration is a commonly used separation process. Many researchers have looked at the different properties affecting the performance of filter media and many methods have been considered for testing their efficiency. The performance of a filtration process is mainly dependent on the status of the filter medium and its ability to act as perfect barrier within the process, and from there arose the importance of defining its properties and integrity. In this research we are looking at the bubble point test as one of the more useful, economical tests for examining a particular type filter medium. 0.2 μm, 5 μm and 12 μm Nuclepore track etched membranes were used in this research as their pore dimensions are close to cylindrical. The main parameters investigated were the minimum and mean pore size in addition to the bubble point. Two types of porometers were used in this research, the PMI and the Coulter II, and the results obtained by both were in good agreement with the ranges specified by the manufacturers. The selection of Nuclepore track etched membranes is made due to the uniqueness of the shapes of their pores. The cylindrical shape of the pores in this type of membranes simplifies the approach towards modelling the bubble point test, and thus understanding the microhydrodynamics occurring inside the membrane. This knowledge is obtained from this research by simulating both velocity and pressure profiles as well as gas-liquid interaction inside single and multiple pores, thus providing comprehensive understanding on the behaviour of the gas and the liquid phase inside the membrane. Such knowledge will help improve the design for a better system to accurately measure the bubble point test. Different mathematical methods can be applied, but the ability of the penalty scheme finite element method in dealing with complex geometries and such complex phenomena made it the preferred method. On the other hand the use of the volume of fluid method to detect the interfacial surface between the gas and the wetting liquid inside a pore microstructure has not been fully addressed before and thus considered as a novel part of this research.

In the present study ultrafiltration (UF) of inorganic salts in the presence of a polyelectrolyte in the feed solution was investigated. Cellulose acetate membranes completely impermeable to the polyelectrolyte were selected with pore size 5-20 nm. At low concentrations of polyelectrolyte, a gel layer on the membrane surface does not form. At such low polyelectrolyte concentrations the concentration of inorganic salt in the permeate stream can be higher than in the feed solution. This salt concentration effect is the reverse of what is obtained with conventional membrane processes; where the permeate salt concentration is lower, or equal, to the salt concentration in the feed solution. It is shown that when ultra-filtering inorganic salts in the presence of a polyelectrolyte, the ratio of salt concentration in the permeate to feed is improved when the initial salt concentration in the feed solution is low.

No description available.

Monofilament cloths are used as the separation media in filtration; woven wire cloths or screens are also used as the media in filters or to enhance the integrity of the filter medium in, for example, filter cartridges. A better understanding of the flow pattern in the woven structure is essential in examining the initial stages of cake filtration as well as the effect of weaves on fouling phenomena within a filter cloth. Due to the complex geometry of a woven cloth, three-dimensional modelling is necessary to correctly visualize the structure of the flow and hence to predict pressure losses. The modelling in a three-dimensional domain was handled using a finite element method which is known to cope with flow domains in complex geometries very effectively. The governing equations of continuity and momentum were solved by a mixed U-V-W-P finite element method and in conjunction with a first order Taylor-Galerkin scheme for temporal discretization. A secondary solution scheme based on a continuous Penalty finite element method in conjunction with theta time stepping method was also used to solve the governing equations. Two robust and reliable computer tools based on these sound and robust numerical techniques have been developed to simulate Newtonian and non-Newtonian fluid flow through a woven wire mesh. Purpose-designed test cases were used to validate the capability of the developed algorithms and were found to give expected numerical predictions. A selection of domains was used to investigate the effect of weave pattern, aperture to diameter ratio and Reynolds number on flow pattern and pressure drop. Based on these domains, simulations were successfully conducted to investigate fluid flow through four basic pore types in a plain weave, twill weave and satin weave. The flow fields in the interstices were illustrated using a commercial graphics software package. The results showed that the weave pattern has a profound effect on the fluid flow pattern and pressure drop across the wire mesh. Simulation results showed that plain weave gives the lowest pressure drop, while satin weave gives the highest pressure drop across the woven cloths. Fluid flow through a plain weave was further investigated in conjunction with the experimental studies of Rushton (1969) using water and Chhabra and Richardson (1985) using shear-thinning fluids. Simulations were tested against experimental data extracted from both studies. The close agreement of the results to those of the available experimental data in literature showed the accuracy and the reliability of the predictions. Personal communication with industrial experts and woven cloth manufacturers have confirmed industrial practice, whereby a plain weave is primarily used due to its lowest flow resistance. This showed that the developed model is capable of generating accurate results for flow of both Newtonian and non-Newtonian fluids through filter media. The model can be used by design engineers as a convenient and effective Computer Aided Design (CAD) tool for quantifying effects of pressure drop. The model can also be extended to describe particle capture on/in the wire mesh and woven filter cloths.