Online ISSN : 1881-5790
Print ISSN : 0914-2843
ISSN-L : 0914-2843
Volume 23 , Issue 1
Showing 1-3 articles out of 3 articles from the selected issue
  • Daisuke NISHIURA, Atsuko SHIMOSAKA, Yoshiyuki SHIRAKAWA, Jusuke HIDAKA
    2009 Volume 23 Issue 1 Pages 53-65
    Published: March 15, 2009
    Released: December 02, 2009
    The formation mechanism of particle packing structures in a drying process was analyzed by using a simulation for the drying behavior of particulate suspensions coupled with CIP method and DEM. It was cleared by the detailed investigation of the influences of suspension characteristics and particle properties that the high dens packing structure of particles was formed by the following three kinds of actions. a) The promotion of a rearrangement with increasing of ζ potential or decreasing of Debye length which define an interparticle interaction. b) The formation of ordering structure of particles in liquid with increasing of initial particle concentration of suspensions before drying. c) The increase of vertical capillary force with increasing of liquid surface tension and improving of particle wettability. On the other hand, the effect of particle surface roughness on particle packing structure was negligible because repulsive forces strongly acted on interparticle in liquid by hydrodynamic interaction and electric double layer. Polydisperse suspensions containing particles whose geometric standard deviation is larger than 1.1 formed high dense packing structures with increasing of the deviation of particle size, however, those particle beds were structurally heterogeneous in which particle size distribution became different at each height section.
    Download PDF (2320K)
  • Tadashi NARABAYASHI, Toshihiro MURASE, Youichiro SHIMAZU
    2009 Volume 23 Issue 1 Pages 66-76
    Published: March 15, 2009
    Released: December 02, 2009
    Nuclear power plants have a number of advantages in that "nuclear power plants are environmentally acceptable" as they do not produce carbon dioxide, and fuel loaded in a reactor core has a stockpiling effect to be advantageous in terms of Japan's energy security. This system is based on a small PWR of 30MWth thermal output. It's maximum electrical output is 10MWe. This system aims to supply all energy for life, for example, heat, electricity and hydrogen for fuel cell car, for 2000 to 3000 houses. This system assumed to be built on high latitude like Hokkaido. To confirm the simulation result, the heat transport experiment was carried out. In small size hot water pipeline using metal pipe with polyurethane thermal layer, the feed-water temperature and return-water temperature were measured. As a result, the water temperature was kept high enough, and this thermal calculation method was applied for actual size pipeline. The result of heat loss calculation was about 1 °C / 5km.
    Download PDF (4401K)
  • Kei ITO, Tomoaki KUNUGI, Hiroyuki OHSHIMA
    2009 Volume 23 Issue 1 Pages 77-84
    Published: March 15, 2009
    Released: December 02, 2009
    Numerical simulations of gas-liquid two-phase flows are frequently employed by a lot of researchers to evaluate complicated two-phase flow phenomena. In fact, we also have studied the applicability of the numerical simulation to GE (gas entrainment) phenomena on gas-liquid interfaces. In our study, we are developing a high-accuracy gas-liquid two-phase flow simulation method to achieve direct simulations for the GE phenomena. Since the GE phenomena is highly affected by local flow path geometries near occurrence regions of the GE phenomena, non-orthogonal meshes are employed in our study to achieve accurate modeling of the flow path geometries. In addition, we are focusing on mechanical balance conditions at gas-liquid interfaces because it is well-known that unphysical behaviors can be induced easily by mechanical unbalances at gas-liquid interfaces. In this paper, appropriate formulations satisfying rigorous mechanical balances between surface tension and pressure are derived on non-orthogonal meshes. In the formulations, a surface tension potential is introduced based on the Laplace equation as a consistent form with a formulation of a pressure jump condition at gas-liquid interface. In addition, for numerical simulations of stratified flows, a gravitational potential is also introduced to formulate a discontinuity of a pressure gradient at gas-liquid interface. Finally, the new formulations are verified by calculating a stationary gas-bubble in liquid. As a result, the present method succeeds in eliminating perfectly unphysical phenomena (spurious velocities) induced by inappropriate formulations. The present method also gives a physically appropriate simulation result near stratified gas-liquid interface where conventional methods (without the appropriate formulations) fail to eliminate occurrences of unphysical phenomena.
    Download PDF (1239K)