Modelling of gas interstitial velocity radial distribution over a cross-section of a tube packed with a granular catalyst bed

Abstract

A mathematical model of gas flow within a tube packed with a granular bed was formulated. The solution of the model represents the local interstitial gas velocity as a function of the geometrical, aerodynamic and physical parameters of the system, which are usually known, and of an empirical model parameter—the local effective viscosity. This parameter is related to the gas kinetic energy dissipation occurring due to the friction on the surface of the elements of the bed and of the tube wall, and also to the shear stresses associated with the molecular and turbulent motion and the radial dispersion in the gas stream. A method for determining the radial distribution of the effective viscosity is proposed, which is based on measurements of the radial profile of the superficial gas velocity just above a cross-section at the end of the bed. The effects of granule diameter and gas flow rate on the effective viscosity radial distribution were examined and a correlation was formulated which can be employed in computations to predict the radial distribution of the interstitial gas velocity.