Influence of bundle porosity on shell-side hydrodynamics and mass transfer in regular fiber arrays: A computational study

Abstract

CFD predictions of the effects of a fiber bundle porosity on shell-side hydrodynamics and mass transfer under conditions of steady laminar flow were obtained. Fluid was assumed to flow around regular hexagonal or square arrays of cylindrical fibers of different pitch to diameter ratios, yielding bundle porosities ranging from the theoretical minimum up to ∼1. A large number of axial, transverse and mixed flow combinations were simulated by letting the axial and transverse flow Reynolds numbers and the transverse flow attack angle vary. Both fully developed and developing conditions (entrance effects) were considered. The continuity and momentum equations, along with a transport equation for the concentration of a high-Schmidt number solute, were solved by a finite volume CFD code. Fully developed conditions were simulated by the well-established “unit cell” approach, in which the computational domain is two-dimensional and includes a single fiber with the associated fluid, periodic boundary conditions are imposed between all opposite sides and compensative terms are introduced to account for large-scale longitudinal or transversal gradients. Developing flow was studied by using a fully three-dimensional computational domain. Predictions were validated against experimental, computational and analytic literature results. The simulations showed that lattices with different porosities exhibit a qualitatively similar behavior, but differ significantly in important quantities such as the Darcy permeability, the Sherwood number and the hydrodynamic and mass transfer development length.