The Navier-Stokes and continuity equations are solved together with Darcy’s law to analyze pure fluid flow through the membrane in a rotary filtration module. Generation of Taylor vortices is neglected limiting the analysis to flows below the critical Taylor number. The pressure differences across the annulus and the membrane are solved independently. By simplication of the mathematical model, two ordinary differential equations are obtained which are solved numerically using a Runge-Kutta method. The theoretical results are compared with the slit approximation of Belfort et al. [2] and with experimental data [3].