The multiphase technology in power plant boiler during last ten years in Japan have been reviewed. The most important events on utility boiler are the appearance of coal fired supercritical sliding pressure operation boiler, the increase in steam pressure and temperature for higher plant efficiency, and the increase in number of gas turbine combined plants. Concerning these events, some key technology were developed in multiphase field. The detailed study on boiling heat transfer in rifled tube realized the vertical tube type boiler, which had more simple furnace wall structure than the spirally wound type ones. The ultra supercritical pressure boiler achieved 5% higher efficiency than the normal pressure ones. The natural circulation waste heat boiler with horizontal evaporating tubes, which enabled low cost construction, was designed under attentive thermal and hydraulic studies, and successfully started to operate. The condensing heat transfer of ammonia-water mixture was investigated and the high efficiency of the mixture cycle was demonstrated through test plant operation. Regarding fuel, coal oil mixture, coal water mixture, and orimulsion were introduced. For clean and efficient usage of coal, PFBC and IGCC are expected as the important future power generation system.
The term “bioreactor” is defined as a reactor in which biochemical or biological reactions are carried out to produce useful substances from raw materials. This term can be applied to fermentors used for the cultures of microbe, animal and plant cells, and to vessels (or columns) containing immobilized biocatalysts such as enzymes, organelles and cells. The chronological aspects and future perspectives in technological development of the bioreactors are described in the present article.
Since slurry transportation systems are very useful to transport bulk materials, the systems are used in transporting ores and tailings in mining industries and in dredging harbors. This paper describes the characteristics of the slurry transportation systems, and the plan and application of the systems, written as follows, in mineral development in Japan. 1) The plan of Ishikari coal slurry tranport pipeline. 2) The hydraulic transportation system in Sunagawa coal mine. 3) The backfill slurry transportation system in cut-and-fill stoping. 4) The Oodate-Noshiro tailling slurry transport pipeline. 5) The pilot plant system of slurry transportation for sediment sand in Sakuma dam reservoir. 6) The manganese nodule mining system using airlift pump by National Research Institute for Pollution and Resources. 7) The control of gas kick and drilling mud flow in drilling well for methane hydrate production.
The aim of this papar is to show the relation between the stability property of the finite difference equation for a linearized system of compressible flow equations and the property of its modified equation, that is the differential equation actually solved by a difference equation, as the eigenvalue problem of the coefficient matrix. Based on a finite difference equation by discretizing the linearized system of compressible flow equations by using the explicit scheme in time and 2 step Lax-Wendroff scheme or central differnce scheme in space, a modified equation of the finite difference equation is introduced. It is shown that the stability condition of the finite difference equation can be expressed by the eigenvalue of the lowest order diffusion term of the modified euation.
The direct numerical simulation is performed on the spherical bubble unsteadily rising through a quiescent liquid. The method is based on a finite-volume solution of the equations on an orthogonal curvilinear coordinate system. The calculations are performed for a bubble rising through a clean liquid and contaminated one. Following the former experimental results, the tangential stress free condition is given for a clean bubble, and no-slip condition for contaminated one. The numerical results are compared with those of the model equation of the translational motion of the bubble, which is often used in numerical models of a bubbly flow. The steady drag, added mass and history terms are checked up by the comparison. It is revealed that the history force effect is negligible for a bubble rising through the clean liquid beyond Re=O (50). From the numerical point of view, the fact that the history force is negligible is quite important, because it reduces the calculation time and memory for a bubbly flow model. For a contaminated bubble, history force effect is not negligible even though the Reynolds number is high enough. It is found that the expression of the history force by Basset kernel gives an over-estimation of the history force for the bubble rising at moderate Reynolds number. This error becomes larger with increasing Reynolds number and it reduces the accuracy to calculate the bubble motion by the model equation.
This paper describes an application of thermography to determine surface temperature of liquid which is moving along a heated wall surface. Breakdown of a thin liquid film is known to cause a problem in the heat transfer surface leading to a serious burnout phenomenon. To develop a technique to prevent the burnout phenomena, the mechanism of the burnout needs to be understand. Thus, we measured transient surface temperature of a thin liquid film using a thermography. Emissivity and absorption coefficients of water, a silicon oil and 1-propanol were determined by comparing its thermocouple measurement. As a result:(1) emissivity of water, a silicon oil and 1-propanol was approximately 0.95 and (2) transient temperature profiles on a liquid surface of wavy flow were obtained.
Carbon dioxide absorption rates into water were measured to determine volumetric mass transfer coefficients, kLa, in bubble and slug flow regimes of gas-liquid two-phase upflow through a 0.030m i.d. vertical tube. Axial local values of kLa decreased rapidly downstream from gas inlet. Axial averaged values of kLa, which is denoted by (kLa)z, were affected by gas velocity, uGO and distance from gas inlet, z, being correlated by the following equations: (kLa)z=0.81uGO1.20Z-0.62
The optical fiber probe technique has been widely used in the analysis of gas-solid fluidized bed phenomena owing to the small size, quick response and flexibility of the probe as well as wide ranges of applicability of the technique as a whole. With potentially equal applicability to gas-liquid and gas-liquid-solid flow systems, this technique has recently witnessed its important role in the multiphase flow research. No systematic, fundamental explanations/guidelines for the usage of the fiber optics, however, are available to our knowledge in the pertaining research field. In this article, we introduce the basic probestructures, characteristics of the obtained signals, the data processing techniques and the range of applicability to further encourage the use of optical fiber techniques “tailored” to the multiphase flow analysis.