伊藤 和宏

To evaluate biodiesel production from microalgae, a flotation experiment was conducted using the living cell culture fluid of the diatom Chaetoceros gracilis using a venturi tube type microbubble generator. We compared the separation performance of three different culture periods: 1, 2, and 3 weeks from the start of cultivation. After 1 week, the cells were in the logarithmic growth phase, while after 2 and 3 weeks, cell growth had reached the stationary phase. The amounts of triacylglycerol (TAG) in the foam on the surface of the fluid tank were measured. TAG increased during the first 20 min after the start of circulation without additional coagulants and pH adjustment. The disruption of cells was achieved simultaneously. The amounts of TAG in the culture fluids at weeks 2 and 3 were higher than those at week 1. C. gracilis cells in the stationary phase accumulated large amounts of TAG and were easy to disrupt by pressure fluctuation in the venturi tube. These results provide insight into the fracture strength and buoyance of cells for efficiently separating the cells from large volumes of culture fluid.

By employing an annular‐cylindrical‐type apparatus operated under a constant cooling rate, melt crystallization is studied to condense a saturated fatty acid (FA) from a binary mixture of the saturated FA with unsaturated FA. In the annular space between the stationary outer cylinder and the rotating inner cylinder, counter‐rotating toroidal vortices, that is, the Taylor vortices are observed. The vortices are found to play a unique role in the solidification of FAs to form a unique wavy layer on the inner cylinder. The mass and heat transfer analysis by numerical calculation reveals that both the velocity and temperature distributions change depending on the position in the annular space because of the centrifugal or centripetal radial flow caused by the Taylor vortices.

食品加工施設の排水は腐敗しやすく，槽底に滞った汚泥から臭気や硫化水素などが発生し，排水処理施設の能力を低下させる．これに対し，高流速で空気を注入する方式のエアレータを用いて攪拌し，好気性処理を安定させる方法を提案した．地下水槽（幅2m×水深1.75m）の底部にエアレータを設置し，曝気中の流速を3軸電磁流速計で測定した．3次元的な循環流が観察され，循環流量は約400 L/min と推定された．また，溶存酸素量（DO）の測定から，良好な酸素溶解効率（OTE）が得られた．さらに，実際の食品加工排水に適用した場合の処理状況について報告した．

We investigate the vapor bubble stability in liquid argon and water using a molecular dynamics simulation. The Lennard-Jones interparticle interaction potential is used to simulate the interaction forces between molecules. The Stillinger' s cluster criterion is employed to classify the vapor molecules evaporated from the bulk liquid. Using this criterion, the vapor molecules are determined to have no neighboring molecules within a 1.23 to 1.32σ radius, where σ is the interaction radius in the L-J potential. The pressure of vapor and liquid phase can be calculated from the virial equation of sate. The stability of bubble is disscussed applying the Young-Laplace equation. The spherical bubble shape is maintained, when the liquid pressure takes the negative value. The thickness of vapor-liquid interface and the number of molecules across vapor-liquid interface are not proportional to the size of bubbles.

In application of micropumps to new fields in chemistry, biology, medical science and others, smaller sizes are supposed to be important rather than higher pump performance. In this study, considering from such a view point, micropumps using rotational and reciprocating motions of magnetic material balls were proposed and studied experimentally. The pump performance, i.e. the relation between flow rate and pump head are measured from liquid level changes in two containers connected to the inlet and outlet of the micropump. For the rotational motion micropump, while the maximum flow rate obtained, ~2 mL/min, is large enough as a micropump, the maximum pump head achieved, ~15 mm, is small even for a micropump. It is desirable to increase the pump head furthermore for this micropump. For the reciprocating motion micropump, the maximum flow rate obtained and the maximum pump head achieved are ~7.5 mL/min and ~625 mm, respectively. These values of the pump performance are sufficient as a micropump. Both the micropumps can be incorporated into microfluidic devices (tips) and can pump arbitrary kind of liquid.

Flow through an air passage of ventilated automotive brake rotor affects the thermal energy dissipation from rotor into atmosphere. In the present work, a velocity profile around a ventilated brake disc was measured using a hot-wire anemometer in order to understand the statistical turbulent property of air passage flow. Three-dimensional velocity components were evaluated at 5 mm outside the disc edge by rotating X-type hot-wire probe. The probe was also tilted corresponding to rotational speed so that it could receive the maximum velocity from disc. The maximum value of both average and fluctuation velocity increased significantly than that of solid disc. The velocity fluctuation profile indicated asymmetric aspect in contrast to the average velocity profile. An empirical one-dimensional model was suggested for evaluation of flow through air passage. The predicted radius velocity agreed with the present experimental results by substituting local angular speed of disc into air circumferential velocity.

高速増殖炉（FBR）の炉心溶融事故（CDA）時に，溶融炉心の一部が冷却材中へジェット状に射出される可能性がある．本研究では, 実機と密度比が同程度の低融点合金と水を炉心溶融物と冷却材の模擬物質として用いた実験を行い, 両者の相互作用を理解し，固化に至るまでの詳細を把握することを目的とする．実験では, 溶融物を水中に自由落下させ, その挙動を高速度カメラで観測した. また, 固化物を回収, その形状, 質量および寸法を計測した. その結果, これまでに溶融物の温度により, 溶融物ジェットの流動の形態を溶融物と水の液-液接触および固-液接触条件に区分することができ, 更には固化物と可視化観測結果から, 界面凝固膜の材料強度を考慮した微粒化物径予測式が構築されている. そこで, 今回は溶融物ジェット界面挙動の詳細な可視化観測から界面凝固膜の材料強度を直接評価することで予測式の検証を試みた.

高速増殖炉（FBR）の炉心溶融事故（CDA）時に，溶融炉心の一部が冷却材中へジェット状に射出される可能性がある．本研究では, 実機と密度比が同程度の低融点合金と水を炉心溶融物と冷却材の模擬物質として用いた実験を行い, 両者の相互作用を理解し，固化に至るまでの詳細を把握することを目的とする．溶融物を水中に自由落下させ, 溶融物の挙動を高速度カメラで観測した. また, 実験後に固化物を回収し, その形状, 質量および寸法を計測した. その結果, 溶融物の温度により, 溶融物ジェットが異なる分散・微粒化挙動を示した. そこで流動の形態を溶融物と冷却水の液-液接触および固-液接触条件に区分し, 固化物と可視化観測結果から溶融物ジェットの流動構造の評価を試みた. 更に界面凝固膜の材料強度を考慮した微粒化物径予測式を構築し, 実験にて測定した固化物の質量メジアン径との比較を行い予測式の検証を行った.