Network Modeling of Flow in a Packed Bed Anto ´nio A. Martins, Paulo E. Laranjeira, Jose ´ Carlos B. Lopes, and Madalena M. Dias Laboratory of Separation and Reaction Engineering, Departamento de Engenharia Quı ´mica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal DOI 10.1002/aic.11047 Published online December 4, 2006 in Wiley InterScience (www.interscience.wiley.com). The characterization of the flow inside a packed bed requires a full description of the pore geometrical characteristics, and of the flow phenomena at local level. A two- dimensional (2-D) network model for describing the flow phenomena in unconsoli- dated-packed beds has been developed. The network model consists of two different types of elements: chambers modeled as spheres, and channels modeled as cylinders. The size distributions of the network elements are obtained considering a geometrical model that uses the porosity, and the average-particle diameter as input data. A flow simulator was developed, based on this network model. Results show that since the in- ertial effects due to connections between channels and chambers are taken into account, this simulator is capable of describing single-phase flow in all the possible flow regimes, from laminar to turbulent. Results also show a good agreement between predicted values of the network model and experimental data available in literature. Ó 2006 American Institute of Chemical Engineers AIChE J, 53: 91–107, 2007 Keywords: porous media, packed beds, network model, nonlinear flow, Ergun equation Introduction Transport and flow phenomena in porous media occur in many diverse areas of science and engineering. Many processes in the chemical industry, such as adsorption, ion exchange, chemical and catalytic reactors, are based on or include a packed bed, usually involving the flow of fluids through a po- rous medium. Better design and operation of these units require a deeper understanding of the mechanisms controlling the trans- port phenomena inside porous media. Among the different aspects that must be accounted for, the influence of the void space structure is one of the most important. 1,2 Prediction of process variables, such as the total pressure drop and the total flow rate, are often based on semiempirical correlations with constants that must be fitted to experimental data. In particular, the Ergun equation has become the standard correlation, but other examples include the Kozeny equation, valid for laminar flow, and the Forcheimer equation, valid for nonlinear flow, 3–8 in which the pressure does not vary linearly with the flow rate through the packed bed. Generally, the extension of these correlations to different situations is not possible because they are based on experi- mental data obtained for a specific system. Also, the study of complex transport phenomena, such as multiphase-flow cannot be done, since no information about the local struc- ture is considered. The inclusion of the local structure increases the adequacy of the model at the cost of greater mathematical complexity. 1,2,9 Due to the random and very complex structure of many packed beds, a simple approximate model of the pore struc- ture, that preserves the main packing features in a mathemati- cally usable form, must be developed. Different approaches have been proposed to model the structure of the porous space of a packed bed or a porous medium, with different levels of complexity, and using different types of experimen- tal information. 1,2 One type of model describes the flow around the porous-medium particles by defining elementary cells to represent the packed-bed local structure. Initially Correspondence concerning this article should be addressed to M. M. Dias at dias@fe.up.pt. Ó 2006 American Institute of Chemical Engineers AIChE Journal January 2007 Vol. 53, No. 1 91