Study on performance and flow field of an undershot cross-flow water turbine comprising different number of blades

Recently,small hydroelectric generators have gained attention as a further development in water turbine technology for ultra low head drops in open channels.The authors have evaluated the application of cross-flow water turbines in open channels as an undershot type after removing the casings and guide vanes to substantially simplify these water turbines.However,because undershot cross-flow water turbines are designed on the basis of cross-flow water turbine runners used in typical pipelines,it remains unclear whether the number of blades has an effect on the performance or flow fields.Thus,in this research,experiments and numerical analyses are employed to study the performance and flow fields of undershot cross-flow water turbines with varying number of blades.The findings show that the turbine output and torque are lower,the fluctuation is significantly higher,and the turbine efficiency is higher for runners with 8 blades as opposed to those with 24 blades.     

Heat transfer and fluid flow of natural convection along a vertical flat plate in the transition region: experimental analysis of the wall temperature field

Heat transfer and fluid flow of natural convection along a vertical flat plate were experimentally investigated in the transition region. Local heat transfer coefficients along a vertical flat plate were measured to distinguish the first transition region. The wall temperature and fluid flow were then visualized using a liquid crystal sheet and water-soluble fluorescent paint. Also discussed are the characteristic statistical quantities with the aid of visualizations for the velocity and temperature fields. It was revealed from a series of experiments that horseshoe-shaped low-temperature patterns appear on the wall and that they play a significant role in heat transfer. When the data was ensemble-averaged it was found that the characteristic time-and-space scales of the patterns are statistically independent of not only heat flux but also the position in which they occur. Moreover, W-shaped flow patterns, which possess three-dimensional and unstable structures, appear in the near-wall region. They play a significant role in the laminar to turbulent transition.     

Purification and molecular cloning of an intracellular 3-hydroxybutyrate-oligomer hydrolase from Paucimonas lemoignei

An intracellular 3-hydroxybutyrate-oligomer hydrolase was purified from a poly(3-hydroxybutyrate)-degrading bacterium, Paucimonas lemoignei. It hydrolyzed the 3-hydroxybutyrate dimer with the highest specific activity of any of the enzymes reported so far. The gene was cloned and sequenced. The deduced amino acid sequence showed that the enzyme is a homolog of the PhaZc of Ralstonia eutropha H16.     

Subnuclear localization of S/MAR-binding proteins is differently affected by in vitro stabilization with heat or Cu2+

The clinical problem posed by pancreatic cancer is introduced, and the epidemiology and pathology of the disease are briefly presented. The natural history of this tumor is then described in order to highlight the deficiencies of current therapeutic modalities. The extremely poor results of the early drug trials are reviewed, followed by a detailed discussion and critique of the trials of novel treatments that include gemcitabine, somatostatin analogs, and tamoxifen. Finally, areas for future development are indicated.     

Amidoxime resins based on poly(acrylonitrile-co-vinylidene chloride-co-divinylbenzene) and their behavior in uptake of uranium from sea water

Amidoxime resins were derived from poly(acrylonitrile-co-vinylidene chloride-co-divinyl-benzene) beads, which were prepared by suspension polymerization of the ternary monomeric mixtures in the presence of 4-methyl-2-pentanone (MIBK) or 1,2-dichloroethane (DCE) as the diluent (porogen), in order to clarify the effect of copolymerized vinylidene chloride on properties of the resulting amidoxime resins. Pore structure analyses of the copolymers as well as of their amidoximated derivatives clarified that MIBK yields larger pores than does DCE and then the latter gives larger specific surface areas than does the former. On the other hand, chemical properties of the amidoximated resins, such as anionexchange capacities and uranyl ion uptake, were not eseentially affected by the diluent species, indicating that both MIBK and DCE as the porogen lead to the amidoxime resins with almost the same ability in recovery of uranium from sea water. The uranium recovery decreased with increase in the vinylidene chloride content, but the decrease in the recovery was minor up to the 10 mol % of vinylidene chloride. It was also clarified that the uranium recovery by the amidoxime resins containing vinylidene chloride is greatly enhanced by the alkali treatment. © 1994 John Wiley & Sons, Inc.     

Measurement of turbulent heat transfer using infrared thermography near ambient conditions and its quantitative error estimation

Infrared thermography was applied to measurement of turbulent heat transfer in order to investigate its applicability under near-ambient conditions. Natural convection along a vertical smooth flat plate and forced convection along a smooth flat plate were realized in a large darkroom, where individual heat transfer coefficients were quantitatively measured using infrared thermography in the laminar, transition, and turbulent regions. The measurement error was then estimated using ANSI/ASME PTC 19.1-1985 measurement uncertainty to confirm the accuracy. It is obvious from a series of application experiments and error analyses that the present technique is useful for estimating turbulent heat transfer quantitatively and dynamically. Infrared thermography is an appropriate measurement procedure for engineering applications because it can be applied to diagnose a two-dimensional and dynamical temperature field instantaneously and nondestructively. © 1999 Scripta Technica, Heat Trans Asian Res, 28(6): 442–455, 1999     

Diagnosis of the leakage point on a structure surface using infrared thermography in near ambient conditions

It is important to check for leakage points of fluids on a surface to maintain and manage various structures satisfactorily. In particular, it is necessary that the leaking walls of a bank, dam, tunnel, pipeline and so on are diagnosed appropriately using some remote sensing technique and that they should be repaired immediately. Recently, infrared thermography for measuring temperature has become attractive in a wide variety of engineering applications. Infrared thermography in near ambient conditions is introduced to check the leakage point and its applicability is estimated by visualizing the temperature field generated around the point. The generated temperature around the leakage point is not usually consistent with the surrounding temperature. When using infrared thermography, we can detect the leakage point at the location where a marked temperature difference occurs.     

Natural convection heat transfer along a vertical flat plate with a projection in the turbulent region

In the present study, the heat transfer coefficients occurring with a projection in the turbulent region of a vertical flat plate were measured experimentally for various projection heights in the range of 0 to 20 mm. The wall temperature and fluid flow fields were also visualized using a liquid crystal sheet and nylon 12 powder, respectively. The average and local Nusselt numbers reach 1.07 to 1.22 and 1.2 to 1.7 times those for pure turbulent natural convection, respectively. The maximum enhancement rates of heat transfer are attained at a position of 2.3 to 3.3 times the projection height from the upper projection surface toward the downstream, and these positions are in good agreement with those of the reattachment of the fluid flow and with centers of dark red regions in the liquid crystal. On the other hand, the heat transfer coefficients in the just upstream and downstream regions of the projection are small compared with those for no projection. By introducing the nondimensional parameter R, the present experimental results are rearranged quantitatively and effectively. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 222–233, 2001     

Study on the efficiency of effective thermal conductivities on melting characteristics of latent heat storage capsules

Improvement of the thermal conductivity of a phase change materials (PCM) is one effective technique to reduce phase change time in latent heat storage technology. Thermal conductivity is improved by saturating porous metals with phase change materials. The influence of effective thermal conductivity on melting time is studied by analyzing melting characteristics of a heat storage circular capsule in which porous metal saturated with PCM is inserted. Numerical and approximate analyses were made under conditions where there are uniform or non-uniform heat transfer coefficients around the cylindrical surface. Four PCMs (H₂O, octadecane, Li₂CO₃, NaCl) and three metals (copper, aluminum and carbon steel) were selected as specific materials. Porosities of the metals were restricted to be larger than 0.9 in order to keep high capacity of latent heat storage. Results show that considerable reduction in melting time was obtained, especially for low conductivity PCMs and for high heat transfer coefficient. Melting time obtained by approximate analysis agrees well with numerical analysis. A trial estimation of optimum porosity is made balancing the desirable conditions of high latent heat capacity and reduction of melting time. Optimum porosity decreases with increase in heat transfer coefficient.