Computers & Chemical Engineering, Vol.48, 135-153, 2013
Systematic mesh development for 3D CFD simulation of fixed beds: Contact points study
In the development of meshes for computational fluid dynamics (CFD) simulations of transport in fixed beds of spheres, particle-particle and wall-particle contact points often present difficulties. We give results for drag coefficient (C-D) and heat flow (Q) for flow past sphere-sphere and wall-sphere contact points, focusing on higher flow rates typical of industrial steam reformers (500 < Re < 10,000). Global methods, in which all particles in a bed are either shrunk or enlarged uniformly, change bed voidage giving erroneous results for C-D. Local methods, in which bridges are inserted or spherical caps are removed only at the points of contact, give much better results for C-D. The bridges approach is preferable for heat transfer, as fluid gaps reduce heat transfer too much, and particle overlaps increase it. A set of graphs is presented to allow estimation of the error introduced by the various methods of dealing with contact points. (c) 2012 Elsevier Ltd. All rights reserved.
Keywords:Computational fluid dynamics;Sphere;Drag coefficient;Heat transfer;Contact points;Packed bed