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Volume 41, Issue 4
Displaying 1-15 of 15 articles from this issue
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Transport Phenomena and Fluid Engineering
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Gabriel Ascanio, Mónica Alcalá, Carlos Guerrero, Philipp ...Article type: Research Paper
2008 Volume 41 Issue 4 Pages 217-226
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSThe role of fluid rheology in forward deformable roll coating was experimentally studied using coating liquids exhibiting a wide range of rheological properties. The emphasis was put on the understanding of the film splitting mechanism and the ejection of droplets at the exit of the coating nip. The flow visualization downstream the coating nip revealed the presence of a meniscus extending from the nip to form a series of filaments, which in some cases broke up ejecting misting droplets. A strong effect of the liquid rheology was observed on the pressure distribution measurements carried out by a dynamic pressure sensor mounted on the rigid roll. It was shown that viscoelastic liquids develop high pressures into the nip and very low pressures at the exit. Elasticity was shown to retard misting.View full abstractDownload PDF (1263K) -
Yuichiro Wakashima, Akira SuzukiArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 227-237
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSA simple microtube heater for supercritical state water or solutions that can operate at up to 873 K and 25–50 MPa has been developed. In this study, the heating process in a Joule heating microtube and the heat transfer inside the microchannel were numerically investigated by a coupled analysis using simplified modeling. The modeled microtube was made of Ni-base alloy 625; its OD was 1.59 mm and the ID of the microchannel was 0.25–0.50 mm. The typical length of the microtube was 200–250 mm. The characteristics of the heat-up process at the microtube wall and the microchannel heat transfer to flowing water were determined through numerical simulations. As a practical low-cost method, a combination of AC voltage charging and a power thyristor was adopted for heater control. It was observed that if the current frequency was over 50 Hz, the fluctuation in the outflow temperature remained below 1.5 K. The heating performance of the Joule-heating microtube heater is restricted by the pressure drop in the microchannel and the maximum temperature for the tube material.View full abstractDownload PDF (1106K)
Particle Engineering
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Jin Park, Seung Bin Park, Seung-Man Yang, Won Hi Hong, Chun Rak Choi, ...Article type: Research Paper
2008 Volume 41 Issue 4 Pages 238-245
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSGelation behaviors of silica suspensions, prepared from 6 grades of commercial colloidal silica (Ludox® series) and sulfuric acid, were investigated rheologically by a small amplitude dynamic oscillation measurement method in which storage and loss moduli were monitored with time. To date, the gel strength of silica suspension/gel in sulfuric acid and its progress with time have not been properly defined, because of their complex rheological behavior such as their weak structure. For the purpose of a quantitative investigation, the time evolution of the storage modulus was measured for the representation of gel strength and its progress related to fluidity decline with time for application to battery manufacture.
A suspension prepared from small-sized silica particles showed high gel strength and accelerated gelation. It was demonstrated that the total surface area in a unit volume of suspension determines the gelation behavior, regardless of particle size in different grades of silica. This implies that high gel strength can be achieved with low content of silica of small particle size.
It was also found that deionized colloidal silica enhances gel strength. This means that sodium ions in the Ludox®, which play a stabilizing role, should be removed in order to form a strong gel. A positively charged surface and chloride stabilizing ions are not suitable for gelled electrolyte, since they accelerate gelation but do not enhance gel strength.
In conclusion, colloidal silica particles of small size and negative surface charge without stabilizing ions should be used for achieving high gel strength in application to batteries.View full abstractDownload PDF (509K) -
Hidetoshi Mori, Noboru Nonaka, Mitsukuni Mizuno, Hiroya Abe, Makio Nai ...Article type: Research Paper
2008 Volume 41 Issue 4 Pages 246-253
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSA geometrical model has been developed to optimize the microstructure of porous composite anode electrodes of solid oxide fuel cells. The model takes into account the coordination number theory applied to a random packing of binary particle mixture, together with the percolation theory introduced to provide percolation paths for electrons and ions. The predictions confirm that the effective triple-phase-boundary (TPB) index deduced from a geometric analysis depends on the pore size as well as the characteristic parameters including particle radius ratio, contact angle and composition ratio. The influence of pore size on the effective TPB index is particularly conspicuous, suggesting that the pore size optimization should improve the effective TPB index significantly.View full abstractDownload PDF (1942K)
Separation Engineering
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Jia-Jan Guo, Chii-Dong HoArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 254-263
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSThe predicting equations for the mass-transfer rate and mass-transfer efficiency in a concentric circular membrane extractor module under concurrent-flow with various barrier locations were theoretically derived by calculating the mass balance on each subchannel. The separation variable with an orthogonal expansion technique extended in power series was used to obtain the analytical solution. The mass-transfer efficiency enhancement in this study is represented graphically with the volumetric flow rate, flow pattern and permeable-barrier location as parameters. Improvements in the extraction rate, extraction efficiency and mass transfer efficiency can be achieved by setting the barrier location moving away from a subchannel thickness ratio of κ = 0.5. The influences of the barrier location, extraction-phase flow rate, raffinate-phase flow rate and the acetic acid concentration of the raffinate phase in the membrane extractor are also discussed.View full abstractDownload PDF (517K) -
Akihiko Ito, Masakuni MatsuokaArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 264-271
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSIn order to understand the effect of face crystallographic orientation of seed crystals on purity drop during optical resolution by preferential crystallization, experiments were conducted using two seed crystals having different faces and at different initial supersaturations. The threonine (Thr)-water system was used and one of the seed crystals used was rod-like surrounded by {210} faces while the other was plate-like with {100} faces. Except for the higher supersaturations needle-like D-Thr crystals were found to appear in the bulk solutions irrespective of the seed crystals, whereas at higher supersaturations thin D-Thr crystals were found only on the {210} faces of the rod-like seed crystals. These thin crystals were not observed on the {100} faces of the plate-like seed crystals at the same higher supersaturations. However with these seed crystals, nucleation of needle-like D-Thr crystals was observed, therefore the mechanism of purity drop depends on the face crystallographic orientation of seed crystals as well as the solution supersaturations. Based on the observed facts, surface nucleation of D-Thr is the cause of purity drop for the rod-like seed crystals at high supersaturations, while bulk nucleation predominates for other cases. The time at which purity drop began was also found to vary with these operating conditions showing the differences in the mechanism of purity drop.View full abstractDownload PDF (2133K)
Chemical Reaction Engineering
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Study on the Electro-Deposition of Platinum on Anodic Alumite Films for Catalytic Combustion of VOCsLifeng Wang, Qi Zhang, Makoto Sakurai, Hideo KameyamaArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 272-278
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSThe electro-deposition method is a novel method for metal catalyst preparation. Platinum supported on an anodic alumite film using the electro-deposition method was applied as a catalyst for the catalytic combustion of VOCs. The effect of the support time on the catalyst preparation was investigated in this work. The results showed that the short-time electro-deposition method was favorable for the preparation of noble metal catalysts, because it could provide high dispersion and high metal surface area. The catalysts developed using the short-time electro-deposition method also express good catalytic activity in the catalytic combustion reactions of VOCs, even with low metal loading.View full abstractDownload PDF (1331K) -
Tadahiro Aita, Yosihiro Watanabe, Takeshi Higuchi, Shimio SatoArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 279-283
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSCuO is immobilized on electrically conductive carbon particles and its electrocatalytic properties in a cationic surfactant solution are investigated. The properties are measured with a sandwich type two-electrode cell and a common three-electrode bulk cell. Measurements with the sandwich type cell show that the immobilization on conductive particles promotes the anodic oxidation of Cu(II) to Cu(III). The properties are also investigated with the bulk cell using organic sulfur- and chloro-compounds as substrates. The immobilized CuO shows higher catalytic activity for the indirect electrolysis of the compounds.View full abstractDownload PDF (948K) -
Maw-Ling Wang, Biing-Lang LiuArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 284-293
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSThe catalyzed S-substitution of 2-mercaptobenzimidazole (MBI or RSH) by tributylamine (TBA) was carried out in an alkaline solution of KOH/organic solvent two-phase medium. Tributylamine (TBA) reacts in situ with the organic-phase reactant, α-bromo-m-xylene (R′Br) to produce a quaternary ammonium salt ((C4H9)3R′NBr or QBr) which is used as the phase transfer catalyst. The reaction is greatly enhanced by adding a small amount of TBA in the presence of KOH. By appropriately controlling α-bromo-m-xylene (limited compound) at low KOH concentration, only the hydrogen atom connecting to the sulfur atom of 2-mercaptobenzimidazole was substituted byα-bromo-m-xylene. A kinetic model was developed in conjunction with the mass transfer of the catalyst (QBr) and the active intermediate (RSQ), as well as the reactions in both the aqueous and organic phases. The two-film theory is used to account for the mass transfer of QBr and RSQ between two phases. The experimental data verify that the mass transfer rate of the species between the two phases is larger than the reaction rate in the organic phase. The organic-phase reaction is the rate-controlling step for the whole two-phase reaction. A pseudo-steady-state hypothesis (PSSH) is employed to simplify the kinetic model, from which a pseudo-steady-state rate law is sufficiently used to describe the experimental data. Effects of the reaction conditions on the reaction rate and the conversion were investigated in detail.View full abstractDownload PDF (599K) -
Byung Heung Park, Il Woo Lee, Chung-Seok SeoArticle type: Short Communication
2008 Volume 41 Issue 4 Pages 294-297
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSMolten salts are regarded as excellent media for the electrochemical processes of metal oxides. The advanced spent fuel conditioning process (ACP) which has been developed at the Korea Atomic Energy Research Institute (KAERI) adopted a LiCl based molten salt for an electrolytic reduction process in order to reduce spent oxide fuels. In this work, the reduction of U3O8 without an electric current was investigated to establish the behavior of U3O8 in a molten LiCl–Li2O salt. The uranium oxide was reduced to UO2 by way of a substoichiometric solid solution of U–O and a lithium uranate in the form of LiUO3 which is produced from reduced form of U3O8 and Li2O in a melt, and the reduction proceeded almost linearly with time until 42 h in the current system of LiCl–3 wt% Li2O at 650°C. However, the reduced UO2 still contained a small amount of excess oxygen even after 75 h of a reduction.View full abstractDownload PDF (470K)
Process Systems Engineering and Safety
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Yogesh V. Hote, D. Roy Choudhury, J. R. P. GuptaArticle type: Letter to the Editor
2008 Volume 41 Issue 4 Pages 298-299
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSRavi Padma Sree and Manickam Chidambaram (2005) have evaluated the robustness of the system with PID controller of order (n = 5) by Kharitonov’s theorem. In this note, it is pointed out that for low-order systems (n ≤ 6), the robustness of the systems can be guaranteed by checking very simple frequency domain conditions based on Hermite-Biehler theorem (Argoun, 1990). So, there is no need to formulate all the four Kharitonov’s polynomials and also no need to calculate their roots. Thus, the computations can be reduced for such class of systems.View full abstractDownload PDF (321K)
Biochemical, Food and Medical Engineering
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Kenta Shirouzu, Tetsuya Nishiyama, Tomohiro Hikima, Kakuji TojoArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 300-305
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSSynergistic effects of sonophoresis and iontophoresis on skin penetration were investigated using vitamin B12 (VB12, molecular weight 1355.4 and non-ionized compound at pH 7.4) as a model drug in the stratum corneum (SC) of hairless mice. Under passive penetration, SC acts as an effective diffusion barrier for VB12 and physical treatment is necessary to enhance skin penetration flux. Ultrasound (US) treatment (frequency of 300 kHz, intensity of 5.21 W/cm2, and pulse mode of 5.4% duty cycle) under sonophoresis increased both VB12 solubility and diffusivity in the skin according to its energy flux [J/cm2] (intensity × treatment time × duty cycle). The penetration flux of VB12 treated with US of 510 J/cm2 was 12 times larger than that through intact skin. Iontophoresis (IP) application increased the convective water flow due to electro-osmosis, and resulted in an increase in the flux of non-electrolyte VB12 with IP (0.3 mA/cm2) by 20 times compared to the flux of passive experiments. Using US and IP combination, a synergistic effect on the penetration flux of VB12 was achieved. This synergistic effect may be caused by a different mechanism than the one responsible for enhancing skin penetration with only US or IP. Thus, the combination of US and IP treatment is an effective method for skin penetration of large molecules which enter into systematic circulation with great difficulty.View full abstractDownload PDF (1099K) -
Masaru Sakata, Takashi Kawai, Shigeto Kayane, Hiroshi OoshimaArticle type: Research Paper
2008 Volume 41 Issue 4 Pages 306-311
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSGlucose-1-phosphate (G-1-P) is a biological product which, along with its derivatives, has various physiological applications. In order to develop an efficient industrial process for G-1-P, enzymatic production of high concentration G-1-P was attempted by using phosphorylase purified from potatoes as an enzyme, several kinds of linear and branched dextrin differing in chain length and a mixture of KH2PO4 and K2HPO4 (Pi) as substrates. Since the maltotetraose is not active as a substrate for production of G-1-P, effective glucan concentration was defined on a basis of moles of glucose (CeG) excluding a segment of maltotetraose from dextrin. Furthermore, since the reaction was a complicated reversible reaction involving many kinds of glucan differing in chain length, the inhibitory effect of a high concentration of substrate for the enzyme, an apparent equilibrium constant Kapp was defined. Kapp was expressed as a function of initial concentration of glucan (CeG,0) and phosphate (CP,0). The concentration of G-1-P finally obtained at the equilibrium (CG1P,eq) could be easily calculated from Kapp regardless of chain length and branch structures of glucan. As a result, a diagram expressing CG1P,eq as a function of CeG,0 and CP,0 was proposed. A high concentration of G-1-P, namely 230 mM G-1-P was experimentally obtained when CeG,0 and CP,0 were 516 and 3000 mM, respectively, and the enzymatic activity was 100 U·mL–1.View full abstractDownload PDF (447K)
Energy
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Yoshikage Ohmukai, Kosuke Fujimoto, Isao Hasegawa, Shigeya Hayashi, Ka ...Article type: Research Paper
2008 Volume 41 Issue 4 Pages 312-318
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSPyrolysis of NaOH-loaded Douglas fir and cellulose has been carried out to determine the effect of sodium hydroxide on the pyrolysis profile. A tar yield of 0 wt% and the char yield of 32 wt% were obtained at a final pyrolysis temperature of 500°C. It was revealed that the amount of hydroxyl groups in the residue significantly decreased at 200°C and that the structure of cellulose was distorted via cross-linking at the same temperature through spectroscopic analyses and diffraction patterns. The cross-linking led to the increase in char yield at 500°C. A detailed analysis showed that char yield from cellulose at 500°C correlated linearly with the degree of cross-linking calculated from the amount of dehydration at 200°C. These results showed a possibility that the pyrolysis profile of biomass may be controlled through an appropriate pretreatment to change the structure of the intermediate.View full abstractDownload PDF (596K) -
Yoshikage Ohmukai, Kosuke Fujimoto, Isao Hasegawa, Shigeya Hayashi, Ka ...Article type: Research Paper
2008 Volume 41 Issue 4 Pages 319-324
Published: April 20, 2008
Released on J-STAGE: April 20, 2008
JOURNAL RESTRICTED ACCESSPyrolysis of Douglas fir with metal compounds has been carried out to examine the effect of metal compounds on the pyrolysis profiles. The profiles dramatically shifted into lower or higher temperatures by adding some metal compounds. On the other hand, the presence of metal chlorides promoted the decomposition of Douglas fir at low temperature. The metal compounds having high hydrophilicity, by which Douglas fir decomposition was shifted toward lower temperatures, caused an increase in char and a decrease in tar through promoting the cross-linking reaction at low temperature. From these results, it can be said that the control of dehydration at low temperature is an essential factor to achieve high char yield with minimizing tar formation.View full abstractDownload PDF (431K)
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