AN IMPROVED MODEL INCORPORATING CONSTRICTION RESISTANCE IN TRANSPORT THROUGH THIN-FILM COMPOSITE MEMBRANES

An improved Wheatstone bridge resistance model for diffusion through a thin film composite (TFC) membrane has been proposed. The constrictio n resistance encountered by the diffusing species in seeking out a por e in the support membrane to diffuse through is quantified. This resis tance model has been validated for a range of parameters against a rig orous two dimensional numerical analysis of the diffusion process thro ugh a TFC membrane. An analytical solution has also been developed for the case when the support membrane matrix can be considered to be imp ermeable. It is shown that when the support membrane surface porosity is greater than 10(-3) but less than 0.6, the accurate prediction of f lux through a TFC membrane requires a two dimensional analysis. It is shown that the improved Wheatstone bridge model with constriction resi stance is accurate through the entire range of parameters.