An Investigation Of Mass Transfer And Heat Transfer In The Two Phase Flow

The moving boundary problems in two-phase flow are commonly found out in the fields of chemical, energy and environmental industry. Not only there are momentum, heat and mass transfer in the process, but also the formation and the development of the interface have a major impact on the behavior of the system. These problems which are inherent in the nonlinear changes and the topology changes of the expansion, contraction, and the bond of the interface make it very difficult to deal with the problems, so it has become a great concern to the field of two-phase flow.In this thesis, theoretical analysis and experimental investigation combining with computer image processing are employed to study the behavior of a single soluble bubble rising in the static liquid and the ice particle natural rising in the solution, which are the typical cases in the two-phase flow moving boundary problems. It included the research on characteristics of the movement and the absorption (melting) of the foam or bubble, the heat transfer performance at the interface and the changes of the interface in shape.Theoretical model was established based on the analysis of previous researches. And then the result was theoretical analysis and solved. In the research on the whole phase interface changes, experimental method was carried out to track and observe the whole process. The rising and absorption (melting) of the bubble (ice particle) were recorded by means of high-speed photography technique. The process of change was analyzed qualitatively and quantitatively by the use of computer image processing techniques. After improving the experimental method, the accuracy of the result was greatly increased, and it has played a key role in the reliability of conclusions.The result shows that as for the single bubble rising in static liquid, in the initial stage, it is non-standard sphere in spiral up. When it is absorbed to a certain extent, its shape tends to become standard spherical and it rose at a constant speed. Similarly, spherical ice particles in liquid rise in spiral up through beginning to the end. At the same time, it spins conversely and totteringly. It shows that when the velocities of the two phases are different, the analysis of the solid phase should not ignore the lateral force. The research on the absorption (melting) law of bubble (ice particles) in the two-phase flow indicates that the moving velocity relative to the fluid and the temperature of the fluid have equal status while they affect the absorption (melting) rates. Image processing analysis and the ice particles weighing experiments have good evidences of this conclusion. It also proves computer image processing technology can be applied to the analysis of the moving boundary layer problems in two-phase flow.