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.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.