Investigation on interphase mixing and flow condensation process in a vertical channel

In this paper, an experimental study is performed on the mixing of superheated gas and subcooled flowing liquid and the subsequent flow condensation process in a vertical visual flow channel using R123 as the working fluid. The flow patterns of the two phase flow in the vertical channel are verified and the flow condensation lengths of the gaseous phase under different operating conditions are obtained. Test results indicate that under the operating conditions in this experiment, the gaseous phase forms a cavity or a film at the gas orifices, and then forms a dispersive bubbly flow in the downstream region. The flow condensation length of the gaseous phase through a single orifice increases approximately linearly with the gas flow rate over a range of 0.35-0.76 m, and it is reduced to a range of 0.27-0.56 m by using multiple gas injection orifices. A computational fluid dynamics (CFD) model is established to simulate the two phase flow and interfacial heat and mass transfer in the channel. The simulation capability and prediction accuracy of the CFD model are validated by comparing numerical results of phase distributions as well as the flow condensation lengths with test data, and satisfying agreements are obtained. This work could be beneficial to the understanding and handling of interphase heat and mass transfer problems in in-tube two phase flows.