CFD modelling of oscillatory flow in columns having different types of internals

Abstract

Single-phase oscillatory, turbulent flow in cylindrical columns having different types of internals is simulated using Computational Fluid Dynamics (CFD). Standard k-ε model is used to model turbulence. CFD model is validated by using experimentally obtained residence time distribution (RTD) curves. The validated CFD model is used to understand the effect of the design of internals on fluid dynamics prevalent inside the column. Five different types of internals - disc and doughnut, slanted disc and doughnut, concave disc and doughnut, convex disc and doughnut, and inflexed disc and doughnut – are evaluated. The internals are compared on the basis of key hydrodynamic parameters such as Peclet number, shear rate, turbulent energy dissipation rate and pressure drop per unit length for the same oscillation velocity. For the same oscillation velocity, convex disc and doughnut internal is found to have minimum axial mixing with minimum shear rate and minimum turbulent energy dissipation rate which makes it ideal for intensification of applications such as homogeneous reactions of positive order. Inflexed disc and doughnut internal is found to have high shear rate, high turbulent energy dissipation rate with moderate axial mixing which makes it suitable for intensification of two-phase applications such as solvent extraction, and absorption.