Editor-in-Chief:
Hiroyuki Honda (Nagoya University)

Associate Editors-in-Chiefs:
Manabu Shimada (Hiroshima University)
Takao Tsukada (Tohoku University)

Editors:
Ryuichi Egashira (Tokyo Institute of Technology)
Jun Fukai (Kyushu University)
Choji Fukuhara (Shizuoka University)
Takayuki Hirai (Osaka University)
Masahiko Hirao (The University of Tokyo)
Jun-ichi Horiuchi (Kitami Institute of Technology)
Eiji Iritani (Nagoya University)
Yoshinori Itaya (Gifu University)
Hideo Kameyama (Tokyo University of Agriculture and Technology)
Masahiro Kino-oka (Osaka University)
Toshinori Kojima (Seikei University)
In-Beum Lee (Pohang University of Science and Technology (POSTEC))
Shin Mukai (Hokkaido University)
Akinori Muto (Osaka Prefecture University)
Nobuyoshi Nakagawa (Gunma University)
Hiroyasu Ogino (Osaka Prefecture University)
Naoto Ohmura (Kobe University)
Mitsuhiro Ohta (Muroran Institute of Technology)
Hiroshi Ooshima (Osaka City University)
Yuji Sakai (Kogakuin University)
Noriaki Sano (Kyoto University)
Masahiro Shishido (Yamagata University)
Richard Lee Smith, Jr. (Tohoku University)
Hiroshi Suzuki (Kobe University)
Shigeki Takishima (Hiroshima University)
Yoshifumi Tsuge (Kyushu University)
Tomoya Tsuji (Nihon University)
Da-Ming Wang (National Taiwan University)
Yoshiyuki Yamashita (Tokyo University of Agriculture and Technology)
Miki Yoshimune (National Institute of Advanced Industrial Science and Technology (AIST))

Editorial office:
The Society of Chemical Engineers, Japan
Kyoritsu Building, 4-6-19, Kohinata, Bunkyo-ku
Tokyo 112-0006, Japan
journal@scej.org

AIMS AND SCOPE:

Journal of Chemical Engineering of Japan, an official publication of the Society of Chemical Engineers, Japan, is dedicated to providing timely original research results in the broad field of chemical engineering ranging from fundamental principles to practical applications. Subject areas of this journal are listed below. Research works presented in the journal are considered to have significant and lasting value in chemical engineering.

Physical Properties and Physical Chemistry
Transport Phenomena and Fluid Engineering
Particle Engineering
Separation Engineering
Thermal Engineering
Chemical Reaction Engineering
Process Systems Engineering and Safety
Biochemical Food and Medical Engineering
Micro and Nano Systems
Materials Engineering and Interfacial Phenomena
Energy
Environment
Engineering Education

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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 efficiencies (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 efficiency 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.

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The purpose of the present study is to investigate the applicability of dynamic analysis of static pressure data to in situ monitoring of the contact line between two immiscible flows in a micro slit. By using pressure taps fabricated for both organic and aqueous phases, the pressure difference between the two phases and the pressure fluctuation are observed for parallel flows of hexane and water. Visual observations of the position of the contact line between two phases performed by using an index for width of organic phase flow frequently show that experimental data deviate from simulation data based on the laminar flow model. The analysis of static pressure fluctuation is important in view of the existence of velocity fluctuations at the confluence and the influence of these velocity fluctuations on the overall velocity distribution.
Fluctuation components of pressure measurement data are analyzed by using the Welch method. The frequency analysis of hexane–water flow shows a distinctive spectrum intensity in the frequency domain at about 7 Hz. Since a high spectrum intensity results from fluctuations in the overall velocity distribution, it is considered that the features of the spectrogram could be associated with analytical results pertaining to visual observations of the behavior of the contact line. Thus, the dynamic analysis of pressure data is shown to provide dynamic information about two parallel flows which could be associated with the dynamic behavior of the contact line.

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Novel enteric-coated solid-in-oil (S/O) microcapsules were developed. The microcapsules contain a hydrophilic bioactive substance encapsulated in a shell made from edible fats. In these microcapsules, food colors or lactoferrin was used as the core substance and solid edible fats were used as the shell materials. The core hydrophilic bioactive substance was encapsulated by liquid-phase drying and liquid-phase hardening. Variations in the rate of disintegration of the microcapsules were due to the differences in the triglyceride content of the edible fats used. The variation in the release rate of the core material from the S/O microcapsules was due to the differences in the solid fat content (SFC) of the shell material. Furthermore, lactoferrin S/O microcapsules, which did not degrade while passing through the stomach and were efficiently absorbed in the intestine, were prepared. The S/O microcapsules developed in this study can be consumed as a food such as dietary supplements. They can be used not only as end products but also as intermediate materials for administering a variety of drugs.

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Periodic temperature cycling is employed to forcibly change the reactor temperature. Such an operation is expected to be a process intensification (PI) method because the reaction rate of a heterogeneous catalytic reaction is enhanced under periodic temperature cycling. A microreactor was employed to investigate the rapid change in the operating temperature. Dehydrogenation of isopropyl alcohol (IPA) under periodic temperature cycling was performed as a test reaction using an anodized aluminum-supported platinum catalyst. The optimal operating temperature conditions for periodic temperature cycling were investigated by analysis of the reaction kinetics and catalytic activity. The rate-controlling step was clarified using the results of the reaction analysis. The time-average IPA conversion under periodic temperature cycling was higher than that under steady-state conditions. These results suggested that the optimal operating temperature conditions for periodic temperature cycling are dependent on the IPA coverage when the surface reaction is the rate-controlling step.

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Aqueous solutions of some kinds of surfactants and counterions are known as viscoelastic fluids. The rheological properties and fluidity of the solutions are significantly affected by the surfactant and counterion concentrations. Thus, the solution is a potential solvent for industrial applications because a drastic change in the fluidity can be realized only through the addition of counterions. In this study, we focused on the characteristics of the fluid flow of viscoelastic surfactant solutions in a mixing vessel. It was found that in the vicinity of the impeller the fluid was actively mixed and contained a large number of laminated fluid lumps, forming onion-like structure. When the elastic force becomes comparable to the viscous force, the micellar network of the surfactant was deformed. Additionally, if the elastic force was not much smaller than the inertia force, the impeller region was covered by a network-deformed fluid and an onion-like structure was then formed. Moreover, a stable onion-like structure was obtained when the impeller rotated as slowly as possible or when the elastic force of the solution was more significant than the viscous one.

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Two-phase bubble flow in a rectangular channel is simulated numerically by computing solutions to the Navier–Stokes equations for two-phase flow. The deforming boundary separating the gas and the liquid is modeled numerically using the coupled level-set/volume-of-fluid (CLSVOF) method. In this study, we confine ourselves to two-dimensional computations in a rectangular domain. Even two-dimensional computations allow the prediction of two-phase bubble flows in a rectangular channel. It is shown that our computational results corroborate the previous study, in which it is reported that the liquid superficial velocity is lower in the region of transition to dispersed flow in a rectangular channel than in a similar transition channel in a circular pipe.

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The drag force acting on a system of densely packed particles is a common issue encountered during the fluidization of particles. In this process, the bulk motion is induced by the drag action of fluid flow. The discrete element method based on the Euler–Lagrange description can provide a realistic estimation of particle–fluid and particle–particle interactions; however, it is not possible to simulate the flow phenomena in a space smaller than a particle size by using this method. However, the study of flow on such a scale is crucial for the drag force analysis. Therefore, in the present study, the immersed boundary method, which is a direct numerical simulation, is used to investigate the drag force by simulating the flow around each particle. In this simulation, particles were positioned according to different types of spatial arrangements in order to represent the different degrees of voidage, and the flow around these particles.

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A simple and effective method was proposed for the fractionation of particles in suspensions. When suspensions were allowed to atomize ultrasonically, particles only having diameters in a limited range were contained in liquid particles formed by the atomization. Liquid droplets containing solid particles were collected to recover very fine solid particles. Aqueous suspensions of silica or bentonite particles were irradiated with a 2.4 MHz ultrasound, and fractions of fine solid particles were collected by recovering the mist used for transferring the liquid droplets. In addition, the separation performance was examined with a synthesized suspension, which was composed of silica particles having diameters of 100, 300, and 1000 nm. The recovered silica particles had diameters less than 300 nm and the cut-off diameter decreased with the addition of a surfactant. The results show high potential for the ultrasonic fractionation of particles using atomization.

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In this study, we experimentally examine the motion of a drop rising through immiscible liquids in countercurrent linear shear flows. We especially focus on the effects of the physical properties, the shear rate scale, and the viscosity ratio on the rising motion of the drop. We show that the motion of a freely rising drop is very sensitive to not only the physical properties of the liquids and the shear rate but also the viscosity ratio. Our experiments reveal that the transversely migrating drop can be made to move to the right or left depending on the influence of these parameters.

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In-line defoaming of highly viscous fluids is one of the remaining challenges that needs to be addressed for realizing their industrial use. To overcome the problem of air bubbles in such fluids, the pressure-oscillating defoaming for shear-thinning fluids has been developed. This method is performed by intentionally applying pressure oscillation to a fluid containing a bubble to produce a continuous and strong local flow around the alternately contracting/expanding bubble, where the shear viscosity has been lowered. On the basis of the success that we achieved using this technique for causing bubbles in a quartz cell to rise faster, we applied it to a branched-flow channel filled with a viscoelastic fluid with a zero-shear viscosity of 90 Pa·s for the purpose of developing an in-line defoaming system.
In this study, the motions of bubbles in a revised flow channel filled with a higher-viscosity liquid (220 Pa·s) were investigated experimentally. In addition, a small air cavity was introduced on the upper side of the flow channel to act as a bubble trap for improving the defoaming performance. We studied the effect of the trap position on the defoaming performance.

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The effect on substrate temperature on the fluid dynamics in a polymer solution droplet evaporating on a substrate is investigated experimentally and numerically. It is found from the experiments that fluid velocities in the droplets increase with increasing initial substrate temperature and with decreasing initial solute concentration. A mathematical model, which takes thermal and solutal Marangoni effects into account, are numerically solved using a finite element method. The calculated fluid velocities agree with the experiment. Both experiments and calculations show that, though thermal Marangoni forces dominate the fluid dynamics, solute Marangoni forces should never be neglected. The calculations predict that solute Marangoni effects are more emphasized with decreasing contact angle.

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The flow and heat transfer characteristics of an ammonium alum hydrate slurry treated with drag-reducing surfactants have been investigated experimentally. Ammonium alum hydrate has a high latent heat of 251 kJ/kg, and its fusion temperature is 51°C when the concentration of ammonium alum in water is 35 wt%. The friction coefficient and the heat transfer coefficient for melting were measured from a pipe flow with a diameter of 13 mm. From the results, it was found that the ammonium alum hydrate slurry treated with surfactants shows the effective drag reduction in a pipe flow. It was also found that the heat transfer of the slurry with the surfactants is reduced slightly; in particular, this was true in the case of a high temperature difference between the slurry and heating water flowing outside a test tube. However, the heat transfer coefficient of the slurry with surfactants divided by pressure loss was very high, and particle growth due to particle agglomeration could be reduced by the surfactants. From this, it was concluded that the ammonia alum hydrate slurry with the surfactant is a promising system as a heat transportation medium.

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In this work, the authors have studied a method for the improvement of the generating efficiency of a gas-turbine combined-cycle system (GTCC) using by-product gas (pretreated blast-furnace gas). The generating efficiency of by-product-gas-fired GTCC is 6% lower than that of LNG-fired GTCC at a combustion temperature of 1573 K. The generating efficiency of the gas-separation energy was improved by +4.4% (η=48.8→53.2%) by removing CO₂ and N₂ from the blast-furnace gas. If this innovative system were applied to steelworks around the world, the potential electricity generation would be 55 billion kWh/year. This would mean a reduction of approximately 45 million t-CO₂/year.

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Hydrogel beads were prepared by the free-radical polymerization of acrylates having poly(ethylene glycol) (PEG) as the side chain. These beads were used in a batch mode for the detoxication of hexavalent chromium (Cr(VI)) in aqueous solutions. The beads adsorbed Cr(VI) and reduced the Cr(VI) to Cr(III) without requiring any reducing agents to be added. The reduction was followed by the spontaneous release of the resulting Cr(III) in the solution. Such behaviour is attributable to a difference in non-covalent interactions between the PEG chains and the two chromium species. The reduction time for Cr(VI) strongly depended on the solution acidity; it varied from 24 h for a 2 N HCl aqueous solution to 10 weeks for a solution with a pH of 6. The gel beads could withstand a minimum of 20 cyclic uses.

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