The progress of the Two-Phase Flow research is divided into four stages. These periods are 1948-1959, 1960-1970, 1971-1979, and 1980-1988. In this 5th Report, a history of the development of once-through boilers, and the related progress of researches on two-phase flow, the development of research on distribution of flow rate in evaporator tubes and dynamic behavior of steam generators in the secod stage has been described.
Neutron radiography (NRG) is a technique which produces images of the internal structure of a body, making use of the attenuation characteristics of neutrons in the materials being observed. Recently, attempts have been made to expand the application of this technique not only to non-destructive testing but also to a variety of industrial and basic research fields. The attenuation of neutrons is large in a light material like water and small in ordinary metals, which difference may make it possible to visualize a multiphase flow in a metalic container. Particularly, the neutron television, which is one of the applied techniques of NRG, is expected to be a useful tool for observing the behavior of two-phase flow, since it produces images in real time. In this paper the basic idea and the method of NRG are presented along with examples of visualization of multiphase flow by NRG.
Prediction of developing and transient characteristics of circumferential and axial film velocities in a horizontal annular two-phase flow is carried out with the FIDAS-3DT computer code developed in Japan that can provide three-field representation in subchannel flow using the full conservative equations and simple constitutive relations. The specifications are those from a reported air-water experiment in a 3.9m by 32mm diameter pipe. Steady, fully developed axial flow rates seem to be over-predicted compared to the experimental results. A corrective procedure is suggested which takes into account the radial variation in the axial velocity profile.