Discrete flow and heat transfer patterns in low aspect ratio bed reactors

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.A 3-D network of voids (NoV) model was developed to study the discrete flow and heat transfer phenomena in multi-tubular packed-bed reactors. The model utilised does not place severe demands on computational resources. Hence, the model can probably easily be developed to simulate a fully packed tube and also a large number of tubes in the case of multi-tube reactors. Illustrative studies of the NoV model on a packed bed of spheres predict phenomenal variations of discrete angular velocities and consequently wall heat transfer coefficients within a single tube. The phenomenal variations of discrete wall heat transfer coefficients within a single tube imply that the different angular sections of the tube will transfer heat at radically different rates resulting in potentially large temperature differences in different segments of the tube. This may possibly result in temperature runaway and/ or hot spots development leading to several potentially unanticipated consequences for safety and integrity of the reactor.