CFD modelling and experimental validation of pressure drop and flow profile in a novel structured catalytic reactor packing

Packed beds of catalyst particles are normally described using models that contain a number of empirical parameters. The development of computer techn ology and CFD models makes it tempting to try to (1) fully simulate the flo w in packed beds to obtain a more detailed understanding of the physical ph enomena that take place in the bed, and (2) to use the CFD solutions to der ive 'simple' correlations suitable for design purposes. In this paper it is shown that a commercial CFD code (CFX-5.3) can be used to predict, with an average error of about 10%, the pressure drop characteristics of packed be ds of spheres that have a tube-to-particle-diameter ratio of 1.00 to 2.00. Packed beds with these unusually low tube-to-particle-diameter ratios can b e used as unit cells in a novel type of structured catalytic reactor packin g, proposed in this paper, that has very favorable pressure drop characteri stics. The error of 10% in the pressure drop prediction by CFD is acceptabl e for design purposes. The CFD model is also able to predict local velocity profiles that were measured with LDA. The CFD results have been used to fi t a simple two-parameter model that describes the experimental pressure dro p data with an average error of about 20%. For a grid-independent CFD solut ion of laminar flow in a packed bed containing only 16 particles, already t hree million cells are required. However, it is anticipated that within fiv e years from now the simulation of a packed bed containing a few hundred pa rticles will be considered a;'standard' problem in terms of memory and calc ulation time requirements. (C) 2001 Elsevier Science Ltd. All rights reserv ed.