An interconnected multi-phase CFD model is developed capable of describing the transient behavior of a coupled chemical looping combustion systems comprising of both air and fuel reactors. The air reactor is modeled as a high velocity riser, the fuel reactor as a bubbling fluidized bed. The models of both reactors are implemented as separate CFD simulations allowing for an exchange of solid mass through time-dependent inlet and outlet boundary conditions as well as mass, momentum, heat and species sinks. The developed framework is applied to a chemical looping combustion system based on Mn3O4 as carrier material in combination with CH4 as fuel gas. Starting from a base case, different system configurations are investigated. The results indicate clearly that interconnected multi-phase CFD models are well suited for the design process of coupled chemical looping systems. (C) 2010 Elsevier Ltd. All rights reserved.