The progress of the two-phase flow research can be divided into four stages. These period are 1948-1958, 1960-1970, 1971-1979, and 1980-1990. In this 8th Report, the development of researches on the flow oscillations and flow instabilities in boiling channels in the latter period of the second period (1960-1970) has been described. And the experimental studies on the flow instabilities in boiling channels related to boiling water reactors conducted at nuclear power laboratories in variuos countries have been introduced.
A review on the macroscopic flow behavior such as bed-density distribution and change in flow regime, as well as mixing and heat transfer, in risers of circulating fluidized beds is briefly made in the paper. It is usually found that formation of dense bed at the bottom or so-called S-shaped bed-density distribution in riser is usually observed in operation at relatively low gas velocity. Such density distribution, however, is easy to disappear with decreasing and/or increasing of solids circulation rate. Thus, it should be noted that the flow behavior and axial bed-density distribution in riser of circulating fluidized bed have wide variety with changing in gas velocity and solids circulation rate. For future work, it will be needed to take account of solid property for better understanding of solids and gas behavior as well as classification of flow regime.
In a gas-liquid two-phase flow, forces such as surface tension, momentum force and gravity affect on the interaction between dispersed phases such as droplets and bubbles, as well as gas and liquid continuous phases. Gas-liquid two-phase flow experiments under micro-gravity environment have been increasingly carried out in recent years using drop shafts, aircraft, and space stations, to evaluate the influence of these forces included in the constitutive equation utilized in numerical analysis. Here the drop shaft is a very useful tool for two-phase flow experiments, especially when microscopic measurement is required as in the confirmation of a constitutive equation for numerical analysis, because there is a very small remaining gravity of 10-4-10-5 g and no horizontal force. This report outlines examples of research being conducted in Japan on a gas-liquid two-phase flow under micro-gravity environment using a drop shaft, with the aim of confirmation of constitutive equation. Research on gas-liquid two-phase flow under micro-gravity environment using a drop shaft as in these examples is expected to be conducted increasingly in the future, shedding future light on the phenomena of gas-liquid two-phase flow.
Granulation techniques have been developed to produce granular materials, such as all forms of granules, small compacts, coating particles, and small grains or prills, for demand application in widely differing industries. A primary objective in this review is to present a generalized accouts of the diverse granulation methods in a systematic way. In the case of size-enlargement of fine powders, there are two principal modes of granulation. One is achieved by tumbling, agitating, or fluidizing raw materials in the presence of liquid binders, and the other includes granulation processes in which materials are forced to flow in a plastic or sticky condition through dies or screens or in molds. The former is especially reviewed from a design viewpoint of granulation processes.
Gas injection through a porous nozzle has been widely utilized in many metal refining processes such as steelmaking processes. Measurements of bubble characteristics specified by gas holdup, bubble frequency, mean bubble rising velocity, and mean bubble chord length in actual molten metal baths are very difficult, and accordingly, they have been presumed mainly on the basis of water model experiments. This study was carried out to elucidate whether the bubble characteristics in a molten metal bath can be predicted or not from the information on the behavior of bubbles generated at a porous bottom nozzle placed in a water bath. Mercury was used as the model of molten metal and three kinds of porous nozzles with different pore diameters were employed. Three types of bubble formation patterns were observed with respect to volumetric gas flow rate for each porous nozzle placed in the water bath. The bubble diameter varied over a wide range. In the mercury bath, however, only large bubbles with diameters equivalent to the porous nozzle diameter were generated. This differecne is attributable to the wettability between the porours nozzle and liquid. The bubble characteristics in the mercury bath could not be always predicted from the water model experiments.
In this study, experiments were conducted in order to investigate the effect of noncondensable gas on the condensation heat transfer in a feed-water heater under the conditions of inlet quality 13-100% and inlet air molar fraction 0-1.2%. The thermal resistance on condensation surface was found to be proportional to the local air molar fraction. A transport equation of noncondensable gas and the experimental equation of thermal resistance on condensation surface were added to the previously developed program with a two-fluid model and condensation heat transfer model. Feed-water heater calculations indicated that the effect of noncondensable gas on the heat transfer was negligibly small under the operation conditions of about 30 ppm in a power plant. Keywords: Noncondensable Gas, Condensation Heat Transfer, Feed Water Heater
A concept of Fluid Integrated Circuit (FIC) was introduced which was developed as a particle handling device especially suitable for handling of bio-materials. This device handles particulate materials in a two dimensional micro channel constructed on a substrate using fluid and electrophoretic interactions. As concrete examples, cell fusion device and particle detecting device were shown. A pearl chain of one to one cell pair was easily formed in the cell fusion device. In the particle detecting device, particle detecting and size measurement were performed using the principle of coulter counter. Also a basic study on the integration of these unit components into a single device was described.