Yoshiro Inoue

Osaka University, Suika, Ōsaka, Japan

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Publications (45)33.7 Total impact

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    ABSTRACT: Streak line patterns of several wide-paddle impellers developed by mixer companies in Japan were observed from laminar to turbulent flow regions. The power consumption of all wide-paddle impellers examined was correlated by using the same correlations as in our previous work, but the mixing mechanism of these impellers in the laminar flow region changed greatly with the kind of impeller. It was found that these wide-paddle impellers had distinctive patterns of streak lines depending on the operation conditions. In particular, liquid height greatly affected the streak line pattern. Furthermore, it was found that the impeller Reynolds number was a parameter that controlled the streak line pattern.
    No preview · Article · Jan 2015 · KAGAKU KOGAKU RONBUNSHU
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    ABSTRACT: When a time periodic perturbation is added to a laminar steady flow, fluid mixing effect is sometimes extremely enhanced. In order to clarify the reason, numerical simulations of fluid mixing were conducted for two 2-dimensional and one 3-dimensional flow systems. As a result, it was revealed that for perturbation of constant amplitude the best mixing effect was obtained when the period ratio T-ave/T-p was approximately equal to the golden number (1+ root 5)/2, where T-ave is the mean circulation period of the unperturbed flow and T-p the perturbation period. In addition, the validity of this golden ratio condition for the convective fluid mixing was confirmed in two experiments of the 2-dimensional and the 3-dimensional flows. This phenomenon is due to the fact that the two flows related by the golden period ratio hardly synchronize with each other, and as a result, the streakline acting as the template of fluid mixing distributes uniformly in the fluid mixing region.
    No preview · Article · Jan 2014 · KAGAKU KOGAKU RONBUNSHU
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    ABSTRACT: Mixing time and pattern in the impeller-agitated vessel with two-bladed paddle were investigated at various mixing Reynolds numbers by use of two chemical reactions: ordinary decolorizing experiment with iodine and sodium thiosulfate and Beloousov–Zhabotinskii (BZ) periodical reaction experiment. The periodical steady color-variation in BZ reaction system remained after the sufficient time required for the complete decolorization (that is, ordinary mixing time). The sequential spatial color-patterns obtained in steady periodical variation process were similar to the transitional color patterns observed in the decolorization process. The color-patterns obtained in BZ periodical reaction were consistent with the outline of partially mixed regions where the exchange of substance is relatively slow in the vessel and they depended on mixing Reynolds number. The phase of periodical concentration oscillation in each partially mixed region was shifted with one another in spite of the same period of oscillation. Whether the period and/or phase synchronize or not in each partially mixed region would depend on the relative speed between the exchange of substance and the synchronization of periodical oscillation of concentration there. The periodical reaction could become an available tool for the visualization of distribution of those partially mixed regions containing well and bad mixing regions in impeller-agitated vessel.
    No preview · Article · Oct 2012 · Chemical Engineering Science
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    ABSTRACT: The authors reviewed the correlations of power consumption in unbaffled and baffled agitated vessels with several kinds of impellers, which were developed in a wide range of Reynolds numbers from laminar to turbulent flow regions. The power correlations were based on Kamei and Hiraoka's expressions for paddle and pitched paddle impellers. The calculated correlation values agreed well with experimental ones, and the correlations will be developed the other types of impellers.
    Preview · Article · Apr 2012 · International Journal of Chemical Engineering
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    ABSTRACT: The slurries-containing tetra- n -butyl ammonium bromide (TBAB) solution and its semiclathrate hydrate have attracted a lot of interest as latent heat transport media. These hydrate slurries contain some microparticles of crystal, and the size and shape of these hydrate particles could affect the mobility of slurries. Hence, it is essential to investigate the efficient hydrate-slurry preparation methods and the effect of hydrate particles on the fluid property of slurries for the application to latent heat transport media. In the present study, the effect of agitation on particle size distribution and aggregation of particles was studied to prepare easily flowing TBAB hydrate slurries that were suitable for fluid transport. First of all, the effects of impeller rotational speed and impeller type on the particle size and frequency of aggregation were investigated. The results suggested that the particle size distribution and the frequency of particle aggregation are strongly affected by the intensity of shear rate and its uniformity, which was controllable with impeller type and its rotation speed.
    No preview · Article · Mar 2012 · International Journal of Chemical Engineering
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    ABSTRACT: Fluid mixing is generally judged to be complete when two or more different fluid materials are uniformly distributed over the whole system. In practice, mixing time in mixing processes is often measured by detecting color change due to a chemical reaction. However, the conceptual mixing time does not necessarily coincide with the time of completion of color change. In the present study, we reconsidered the relation between the conventional concepts of fluid mixing and experimentally measured mixing time. In addition, by comparing the difference in the spatiotemporal concentration change between an irreversible decolorizing reaction and a reversible color reaction, we investigated the possibility that mixing times measured by use of these reactions may differ. Experimentally, the completion time of color change in the reversible reaction was found to be longer than that of the irreversible reaction. In a reversible reaction, an initial color change may be reversed until the concentration becomes uniform in the system. Hence, the completion time of color change agrees well with the mixing time in a reversible reaction. On the other hand, in an irreversible reaction, a region once decolorized cannot be colored again even if the concentration in the system is not homogeneous. Thus, error may arise if an irreversible reaction alone is used to conclude that mixing is complete. Moreover, the difference in mixing time measured by irreversible and reversible reactions becomes larger as Reynolds number increases.
    No preview · Article · Jan 2012 · KAGAKU KOGAKU RONBUNSHU
  • Shunsuke Hashimoto · Atsuki Sando · Yoshiro Inoue
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    ABSTRACT: Zigzag microchannels have been commonly used in microreactors and micro total analysis systems (μTAS). In the present study, the mixing performance of four special types of zigzag channels was compared. These channels had m successive 90° bends in the same direction, followed by m successive 90° bends in the opposite direction; this pattern was repeated numerous times. The mixing effciencies (as Reynolds number, Re) under various flow conditions of the zigzag channels (having m=1, 2, 3, or 4) were experimentally determined in the following two ways. First, the mixing patterns were visualized by means of laser-induced fluorometry (LIF). Second, the required length for complete mixing was measured by means of a decolorizing reaction. The results revealed that the mixing eficiency became high with an increase in m, and the effect of convective flow by bending in the same direction is large for 150<Re<250.
    No preview · Article · Jan 2012 · Journal of chemical engineering of Japan
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    ABSTRACT: The storage rate and amount of hydrogen in tetrahydrofuran hydrate were investigated by means of pressure-volume-temperature measurement under three temperature conditions. The absorption process of hydrogen in tetrahydrofuran hydrate was expressed as a dynamical model based on classical shrinking core model, which included two steps: hydrogen inclusion (containing adsorption, entrapment, and delocalization processes) at the surface of tetrahydrofuran hydrate and hydrogen diffusion through the formed layer of hydrogen+tetrahydrofuran mixed hydrate. The rate constant of surface reaction and/or diffusion coefficient of hydrogen depended on the porosity of small cages in tetrahydrofuran hydrate at equilibrium state. The storage amount of hydrogen at all temperatures would reach the maximum value of 2.0 mol (hydrogen)/mol (tetrahydrofuran) at a certain pressure. At the same pressure, the storage amount of hydrogen increases as the temperature decreases.
    No preview · Article · Jan 2012 · Journal of chemical engineering of Japan
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    ABSTRACT: In a laminar flow in a mixing vessel, the velocity distribution is decided deterministically. When a blade rotates at a constant speed in a vessel, the velocity has perfect time-periodicity. In this convective mixing, there are definite rules controlling the fluid motion, and they are repeatedly applied. This mixing process is considered to be a deterministic process for which templates exist, and by the repeated use of them the mixing pattern is gradually develops. These templates are the time-invariant streaklines and the streak surface made by their assembly. The various forms of mixing blades and the use of baffles determine the curvature of the streaklines and the undulation of the streak surface as their assembly. Their deformations enhance fluid mixing in various manners. This study focuses on the geometry and the deformation of streaklines and the streak surface are focused. Through this, the mechanism of laminar fluid mixing in a mixing vessel and its enhancement effects on fluid mixing are clarified.
    No preview · Article · Jan 2012 · KAGAKU KOGAKU RONBUNSHU
  • Shunsuke Hashimoto · Kazuya Natami · Yoshiro Inoue
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    ABSTRACT: Enhancement mechanism of mixing with baffle in agitated vessel using rotated two-bladed paddle impeller was investigated under a laminar condition. In mixing pattern, the toroidal isolated mixing region in the baffled vessel becomes distortive and much smaller than that of unbaffled vessel. From the visualization of streak cross-sections in the baffled vessel, interestingly, the renewed streak folds (streak lobes) are generated at the vicinity of baffles in both the vertical and horizontal cross-sections. These behaviors of streak are unlike the unbaffled case that the streak stretches straightforwardly. The streak lobe is known as the mixing template that its number and size are key factor for laminar mixing in agitated vessel. The results suggest that baffles can effectively transform the circumferential flow to vertical and/or radial flows. Consequently, in the baffled vessels, not only the vicinity of vessel wall but also the tip of baffles can become the origination of streak lobe formation, and folds of streak in the vertical and circumferential directions are further enhanced with baffles.
    No preview · Article · Oct 2011 · Chemical Engineering Science
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    ABSTRACT: Fluid mixing is normally deemed to be complete when the different fluid matters are uniformly distributed through the whole system. In a mixing system where a spontaneous and periodic reaction such as the Belousov-Zhabotinskii reaction (BZ reaction) takes place, however, all small fluid elements in the system can possess not only material characteristics such as the amount of reactants, but also information characterizing the dynamical mode, such as the period and the phase in the periodic concentration change. Moreover, this information can propagate to surroundings through short-range interactions without any fluid motion. In the fluid mixing operations accompanied by the BZ reaction, therefore, we can observe a different space-temporal concentration distribution from that in the usual fluid mixing system. In this study, by comparing the differences in the space-temporal concentration pattern change among a decolorizing reaction, a reversible color reaction, and a BZ periodic reaction, we consider the necessity of reconsidering the normal concept of fluid mixing.
    No preview · Article · Jan 2011 · Kagaku kōgaku ronbunshū
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    ABSTRACT: In the case of laminar mixing in stirred tank, the mixing pattern formed is determined by the streakline originating from the tip of the impeller, and with time its profile approximates the shape of the streakline. An accurate understanding of the configuration of the streakline is therefore important in analysis of the mixing mechanism. In chaotic flow field where global mixing occurs, the fluid trajectory tends to expand exponentially in a particular direction, and it is therefore difficult experimentally to visualize a streak as a "line" because the streak behaves as a "sheet" that has helical envelope. In the present study, we have developed a novel technique to visualize distinct streaklines in a three-dimensional flow field. In this technique, the expansion of streaks is suppressed by the surface tension of surfactant molecules in the tracer fluid, thus allowing the visualization of distinct streaklines generated from the tip of the impeller blade in a stirred tank. This streakline can exist stably and remain in the form of a line for a long time, and there is little leakage of colored component due to the effect of molecular diffusion.
    No preview · Article · Jan 2011 · Kagaku kōgaku ronbunshū
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    ABSTRACT: In the present study, isolated mixing regions (IMRs) in an agitated vessel using a paddle or disk-turbine impeller have been visualized experimentally, and their structural properties and formation mechanism are investigated in detail. A set of thin filaments spirally wrapping around the core of a toroidal isolated mixing region is observed under laminar-flow conditions, where the Reynolds number is smaller than 60. This filament rotates in both directions of horizontal and vertical circulating flows. The three-dimensional geometrical structure of a filament in an IMR depends on the periodical perturbations caused by the rotating impeller. We have succeeded in the determination of the three-dimensional geometrical structure of a filament in an IMR based on the relationship between the movement of a fluid particle and filament numbers and/or wire turns. Interestingly, the wire turns of filaments are opposite to movement of fluid particles.
    No preview · Article · Jan 2011 · Journal of chemical engineering of Japan
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    ABSTRACT: The three-phase equilibrium (pressure−temperature) relation of the difluoromethane + water binary system containing gas hydrates was measured in the pressure range from (0.20 to about 11.0) MPa and temperature range from (275.15 to 300.15) K. On the basis of each three-phase equilibrium curve, the quadruple point which consists of gaseous and liquid difluoromethane, water, and hydrate was determined as 1.45 MPa and 293.16 K. The in situ Raman spectroscopy under the three-phase (gas, water, and hydrate) equilibrium conditions showed that the crystal structure of difluoromethane gas hydrate was structure-I, where both small and large cages were occupied by the difluoromethane molecule. The overall hydration enthalpy of simple structure-I difluoromethane gas hydrate under the three-phase equilibrium conditions was evaluated by means of the Clapeyron equation.
    No preview · Article · Aug 2010 · Journal of Chemical & Engineering Data
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    ABSTRACT: The three-phase equilibrium (pressure−temperature) relations were measured for the hydrofluorocarbon (HFC) (1,1,1,2-tetrafluoroethane (-134a), pentafluoroethane (-125), or 1,1,1-trifluoroethane (-143a)) + water binary systems containing gas hydrate. The measurements were performed in the pressure range up to 10.0 MPa and the temperature range of (273.15 to 295.15) K. The invariant quadruple points (gaseous HFC, liquid HFC, aqueous, and hydrate phases) were located at 283.19 K and 0.416 MPa (HFC-134a), 283.95 K and 0.930 MPa (HFC-125), and 283.33 K and 0.838 MPa (HFC-143a), respectively. The enthalpies of hydrate dissociation to gaseous HFC and water were calculated with the Clapeyron equation, and the value was about 140 kJ·mol−1 for all HFC hydrate systems.
    No preview · Article · Aug 2010 · Journal of Chemical & Engineering Data
  • Yoshiro Inoue · Shunsuke Hashimoto
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    ABSTRACT: Because the flows in agitated vessels are usually three-dimensional, unsteady, and asymmetric, the explicit interpretation of the fluid mixing mechanism as a deterministic process has been difficult even if the flows are laminar. In this study, we have investigated the shape and dynamical behavior of the streakline from the edge of a paddle impeller, and have proposed that the streakline constructs the template for mixing pattern formation. By examining the template, we have explained the mechanism by which the fluid mixing patterns on r-z, Θ -z, and Θ -r spaces are formed according to deterministic rules. Streaklines lie on a multi-spiral surface that densely covers the whole mixing region, and each forms many lobe structures. Because the streakline lobes invade into other lobes to make a nesting structure, they can densely cover the whole 3-D mixing region and systematically the fine mixing pattern according to the mixing template constituted by the streakline. Moreover, this template is invariant as long as observations are made at the interval of passage of the paddle impeller.
    No preview · Article · Jul 2010 · KAGAKU KOGAKU RONBUNSHU
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    ABSTRACT: In low Reynolds number flow conditions, an isolated mixing region (IMR) consisting of two troidal regions is formed in a stirred vessel, and furthermore one or several string IMRs are occasionally observed surrounding the troidal IMR. The string IMR has a closed spiral curve and rotates around the troidal IMR. The winding number and the mean rotating velocity of the string IMR are generally different from those of the fluid particle orbits. In this study, we explain the mechanism of the string IMR formation where the rotating motion of fluid particles is synchronized with the perturbation of the propagative wave motion caused by the passage of paddle blades. We proposed equations that relate the string number, winding numbers and mean rotational velocities of the string IMR to the rotational speed of fluid particles and the number and rotational speed of paddle blades. These relations were validated by comparison of the calculated results obtained by the simplified flow model with experimental results.
    No preview · Article · Jan 2010 · KAGAKU KOGAKU RONBUNSHU
  • Atsuki Sandou · Shunsuke Hashimoto · Yoshiro Inoue
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    ABSTRACT: Zigzag microchannels are commonly used in microreactor and μ TAS, because they are the simplest structures that can function both as a path for liquid transportation and a fluid mixing device. In ordinary zigzag channels, the bending direction alternates, and as a result, the convective fluid mixing effect at one bend is partially cancelled at the next bend. Therefore, the zigzag channel with m alternating bends does not exhibit m times as much mixing performance as a channel with a single bend even. In this study, the mixing performance of four special types of zigzag channels was compared. These channels had m successive 90° bends in the same direction, then m successive 90° bends in the opposite direction, and this pattern was repeated numerous times. Experiments with channels having m=1, 2, 3, or 4 were performed to determine mixing efficiency and the flow condition as Re number.
    No preview · Article · Jan 2010 · KAGAKU KOGAKU RONBUNSHU
  • Shunsuke Hashimoto · Hiroyuki Ito · Yoshiro Inoue
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    ABSTRACT: Isolated mixing region in agitated vessel with rotated two-bladed paddle impeller and no baffle was visualized experimentally and its structural property was investigated in detail. A set of thin filaments spirally wrapping around the core of the toroidal isolated mixing region is observed under low Reynolds number conditions, which is smaller than 60. Three-dimensional geometrical structure of filament in isolated mixing region depends on the periodical perturbations caused by the rotating impeller. We have succeeded in the determination of three-dimensional geometrical structure of filament in isolated mixing region based on relation between the movement of fluid particle and filament numbers and/or wire turns. Interestingly, the wire turns of filaments are opposite to movements of fluid particles.
    No preview · Article · Dec 2009 · Chemical Engineering Science
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    Yushi Hirata · Takahiro Dote · Yoshiro Inoue
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    ABSTRACT: Measurements of power and mixing time were conducted in particle suspensions by using a mixing system with a disk impeller reciprocated up and down in a cylindrical vessel. In a dilute suspension of particle volume fraction, φ, less than 0.2, the power number was almost the same as that in mixing homogeneous liquids but the time required for fluid mixing was decreased with increasing φ. In the suspension of φ equal to 0.01, the mixing time was well correlated with the gravitational settling velocity of the suspended particles. In a dense suspension of φ larger than 0.3, the power number increased appreciably and longer time was required for fluid mixing. From the variations of mixing time with the power input per suspension volume, it has been confirmed that the energy required for fluid mixing in a dilute suspension of φ less than 0.2 is smaller than that for mixing without particles. This suggests that the gravitational potential energy can be utilized for enhancing fluid mixing by the particle motion relative to the fluid motion.
    Preview · Article · May 2009 · Chemical Engineering Research and Design