Bubble Size Distributions and Radial Profiles in Vertical Pipe Flow

The paper presents a method for the prediction of the radial gas fraction profile from a given total bubble size distribution. The method is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. A large number of bubble classes is assumed. Based on the radial profile of the liquid velocity, radial distributions are calculated separately for all bubble classes. The resulting local bubble size distributions can be used by models for bubble coalescence and break-up. It is supposed, that the attempts for a one-dimensional modelling of bubble coalescence and break-up suffer in case of pipe flow from neglecting the radial profiles of the particle densities for the single bubble classes. The model is the basis of a fast running one-dimensional steady state computer code. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates.