Abstract
The mass transfer in two-phase flows depends significantly on the concentration gradient around the dispersed particles and the contact time between the two phases due to the local hydrodynamics of the system which are closely related to the rising velocity of the gas bubbles in the swarm.
The common equations for calculating the slip velocity which take into account the gas void fraction and the velocity of a single free-falling (or rising) particle lead to differences between the theoretical and the measured slip velocity of up to 40 percent. The investigation show that the bubble rise path, expressed by a special tortuousity number for the 3D-bubble trajectory, is totally different from the bubble rise path of a single, free-rising bubble. Furthermore it should be possible to find a relationship between the swarm velocity, the flow velocity and the gas void fraction of the two-phase flow, correlated to the swarm turbulences.
