The influence of an external magnetic field on microstructures in a colloidal dispersion composed of rod-like ferromagnetic particles was investigated by means of the cluster-moving Monte Carlo method. The internal microstructures obtained by simulation were analyzed in terms of the orientational distribution functions and the pair correlation functions. The results obtained are summarized as follows. As the magnetic field increases, the particles align in the direction of the magnetic field. In the case of a relatively strong magnetic interaction between particles, chain-like clusters are formed along the magnetic field. However, the aspect ratio of the particles and the magnetic interaction between particles do not affect the orientational distribution of the particles. The chain-like clusters are observed to have two types of structure: a straight linear structure and a step-like structure. The clusters become shorter when the area fraction of the particles decreases, while the number of step-like structures increases when the area fraction of the particles increases. The step-like structure formation can be explained by the potential energy curves depending on the shape of the spherocylinder particles.
A new method to evaluate the mixing pattern of two fluids is proposed making use of multifractal analysis. The geometrical characteristics of mixing pattern are evaluated with two fractal dimensions: quasi-local fractal dimension q and quasi-global fractal dimension f(q). The relation between the two factors is expressed as a spectrum: q vs. f(q). The rigorous multifractal analysis contains the limiting operation to let cell size approach zero. In the present method, however, size of cell remains finite. As a result, it becomes easy to extract geometric characteristics in complex patterns. This evaluation method has been applied to binary mixing patterns, and its effectiveness and validity have been examined.
Experimental and simulation studies have been conducted about the effects of a ring attached to the upper part of the outlet pipe, and a secondary flow injection near the upper plate, on the particle separation performance of the cyclone. From the experimental and the simulation results, a reverse flow region of rotational fluid was found near the outer side of the upper outlet pipe. Attachment of a ring to the upper part of the outlet pipe was quite effective in reducing this reverse flow region, and cut the size of the cyclone changed to the sub-micron region. Optimum values were obtained for the thickness and length of the ring. The use of a ring decreased the descending angle of particle, but the secondary flow injection increased the descending angle. By using both methods, a ring attached at the upper part of outlet pipe combined with a secondary flow injection near the upper plate, a 50% cut size of about 0.6 μm, was obtained. The results of a three-dimensional numerical simulation of partial separation efficiency and particle descending angle qualitatively agreed with experimental data.
A simple method was proposed for estimating drying rate from the material temperature change in a drying process. This method was applied to convective and combined convective-conductive dryings of a thin glass-particle layer, i.e., non-hygroscopic porous slab, and to convective drying of a PVA solution film. The method was proved to be useful except for two cases ; the period when the temperature rise of the drying material is not accompanied by moisture evaporation; and the period when the quantity of moisture evaporating is small with the change in material temperature is extremely small. The proposed method can be applied to estimate drying rate of a coated web in a rapid drying using hot air, where the conventional method of estimating drying rate from mass change data is difficult to apply.
A convective batch tray dryer with hot air recycle was modeled with a drying characteristic curve and series tank model expressing an incomplete air flow in a drying chamber. An estimation method for performance of the dryer was introduced through simulation of the dryer model. Simulation was made with a combined conductive-convective drying process with hot air at 433 K or 363 K. Concurrently with the above, a wide range of humidity was simulated by using a drying characteristic curve of a wet glass-particle layer obtained from combined conductive-convective drying with hot air at 323 K and low humidity. The effects of hot air temperature, air flow rate, recycle ratio, and tank number on overall drying time, total drying energy, excessive drying of layer, and humidity in the drying chamber and the performance of the dryer were found to change greatly at the border values of 373 K for hot air temperature and 0.95 for recycle ratio.
The thermal energy required for CO2 recovery in chemical absorption plants results from three basic chemical properties; the reaction heat of CO2 removal, the vapor-liquid equilibrium, and the CO2 and absorbent reaction rate constant. These properties are each independent from one another, making it difficult to predict the thermal energy that provides the total capability to recover CO2. A mathematical formula for predicting the thermal energy was made by calculating three factors; the heat of reaction of absorbent with CO2, the effective CO2 loading of vapor-liquid equilibrium data, and the degree of CO2 removal calculated from the reaction rate constant. The calculated thermal energy corresponded well with measured data from the Osaka Nanko CO2 recovery plant. This result indicates that this method for estimating the thermal energy required for CO2 recovery is useful for predicting the abilities of new absorbents.
In this study, a new type DDR zeolite membrane was prepared and its gas permeation and separation mechanisms were studied. Gas permeations of single gases and CO2/CH4 mixtures were measured, and the separation performance of the DDR zeolite membrane was compared with those of other membranes. Measurement of the single gas permeance of He, H2, CO2, O2, N2, and CH4 indicated that the permeation mechanism of CO2 was mainly caused by its adsorption affinity on micropore of the DDR, while that of CH4 was caused by the molecular sieving effect of the 8 ring windows of the DDR zeolite. The maximum CO2/CH4 ideal selectivity at 298 K with the constant pressure method and the sweep gas method were respectively 336 and 170 at the feed pressure of 0.2 MPa and the permeate pressure of 0.1 MPa (atmospheric pressure). Single gas fluxes of CO2 and CH4 and separation factor of equimolar CO2/CH4 mixtures were compared at the same partial pressure. Over the whole pressure range, the CO2 flux of single gas measured by the sweep gas method was higher than that of the mixtures, whereas the CH4 flux of single gas showed very little change. The separation factor of CO2/CH4 mixtures measured by the constant pressure method and the sweep method had a maximum value of 106 at feed pressure of 0.6 MPa, and a maximum value of 200 at atmospheric pressure. In compassion with the new type of DDR zeolite membrane has higher CO2/CH4 separation factor and CO2 permeance. We concluded that the DDR zeolite membrane was suitable for CO2/CH4 separation.
We have developed a new method of freeze-concentration for high-concentration liquor. The equipment consists mainly of an ice-maker, which produces mother ice on a rotating cooling drum, and a basket-type centrifuge. Experiments using sea-water (solute concentration of 1.0–3.4 wt%) yielded concentrated liquor with solute concentration of 2.2–10.2 wt% and solute recovery rates of 0.80–0.94. Partial modification of the equipment and optimization of running conditions are expected to raise the efficiency of operation.
Use of an adsorption refrigerator for automobiles reduces the environmental impact of automobiles, because it uses waste heat from the engine as its energy source. The adsorber should have enough structural strength to withstand automobile vibration. Epoxy adhesive was used to fix the adsorbent into heat exchangers in the adsorber, because it has enough strength, and vapor flow resistance is low for its punctiform shape. In this method, it is expected that the specific thermal conductivity of adsorbent layer will increase, because the contact area between adhering adsorbent particles is larger than that of non-adhering adsorbents. At the same time, the adhesive will decrease the specific density of adsorbent, and it will also decrease the diffusion factor of vapor in the adsorbent layer. In this paper, thermal conductivity of adsorbent layer for various values of adhesive ratio, specific density of adsorbent, and diffusion factor of vapor was examined by simulation and experiment. From these investigations, the optimal value of adhesive ratio was estimated to be approximately 10 wt%.
PA-13A (Propane-Air 13A gas) adjusted to the calorific value of LNG by diluting propane-gas with air is very useful as the town-gas in a middle city. But the LPG vaporizer needs to supply PA-13A to houses. In this paper, a pilot plant of a LPG vaporizer using the wind as heat source was designed by considering the energy saving and the characteristics were tested. The vaporizer was designed as the tube bundling of 180 tubes, by assuming that the pool boiling phenomenon occurred in each tube. Each tube had 8 vertical fins and the height was 2 m. The temperature profiles of the tube surface were measured. The measured values of the temperature fairly well agreed with the calculated values and the validity of the design was confirmed. Although the deterioration of efficiency by the growth of frost layer around the vaporizer tube inevitable, it is applicable to supply the gas to a number of houses by setting a few of this vaporizer in parallel and using those alternatively.
To improve the CO2 reforming performance of TiO2 photocatalyst, the influence on the performance of preparation conditions was evaluated for TiO2 films prepared by sol gel and dip coating method. Surface characteristics of coated TiO2 films were observed and analyzed, and the relationship between surface characteristics and the CO2 reforming performance was investigated. As a result, the CO2 reforming performance was found to improve with increasing coating number up to 11, because of increases in the amount of coated TiO2 and, the surface area of the coated TiO2 film. When films with the optimal coating number were fired for 60, 300 or 540 s, the CO2 reforming performance was found to improve with longer firing duration time, because of the increased surface area of coated TiO2 film. When the amount of TiO2 in one coating was varied by adjusting the ratio of the amount of added TiO2 powder to the amount of TiO2 in the sol solution, it was found that the CO2 reforming performance was improved by setting the amount of TiO2 powder to be added according to coating number.
Injection of dry sorbents, such as pulverized hydrated lime, into flue gas upstream of a bag filter is a common method to remove acid gases in flue gas from municipal and industrial waste incinerators. The present work studied the mechanisms and kinetics of the reaction between hydrated lime particles and hydrogen chloride in a short-time differential reactor (STDR) at elevated temperatures of up to 300°C. As a result, it is found that, in humidified gas, there exists a minimum in the final conversion of hydrated lime with respect to the reaction temperature and that HCl concentration affects only the reaction rate without changing the final conversion. Furthermore, XRD analysis of reacted sorbent revealed that CaClOH is the only reaction product; CaCl2 is not produced. Therefore, 1 mol of Ca(OH)2 reacts with 1 mol of HCl, which is commonly reported when Ca(OH)2 is injected into flue gas of incineration plants.
We studied the phase-transfer catalytic activity of hexaalkylguanidium salts, the final products of guanidine alkylation. We examined the catalytic activity of 12 kinds of guanidine salt in reactions starting in an organic phase or in an aqueous phase. The comparative control was tetrabutylammonium iodide (TBAI), a quaternary ammonium salt. In reactions starting in an organic phase, catalytic activity was mostly in the order of guanidium salts≧TBAI, indicating that more lipophilic salts have higher catalytic activities among the guanidium salts. In contrast, in reactions starting in an aqueous phase, catalytic activity was mostly in the order of TBAI>guanidium salts; more lipophilic salts had higher catalytic activity among the guanidium salts. However, in all the reactions, hexabenzylguanidium salts showed little catalytic activity. We found the cause to be the hydrolysis of hexabenzylguanidium salts by a strong base under conditions for phase-transfer reaction. In addition, we considered the mechanism of the catalytic activity of guanidium salts in relation to their structures.
Today's cosmetics market in Japan is seeing a strong demand for whitening agents from women wishing to remove pigmentations from facial skin. At the same time, we and other researchers are trying to produce useful materials (e.g., medicines and cosmetics) from the distillation remnants of shochu spirits, because the disposal of these remnants in the sea will be prohibited from 2007. In the present study, we carried out basic research for development of a cosmetic whitening agent from powdered barley shochu distillation remnants using B16-F0 melanoma cells at a safe low density of 10 μg/mL. The findings were as follows: (1) B16-F0 melanoma cells were visibly whitened; (2) melanin production by the cells was markedly depressed; and (3) tyrosinase activity of the cells was strongly inhibited. These findings indicate the potential applicability of powdered barley shochu distillation remnants in cosmetic whitening agents.
On the basis of experimental and numerical analysis, it was shown that a trapezoidal cross-section enhanced convective mixing in a zigzag microchannel. In a rectangular channel, a pair of secondary flow vortexes arranged vertically appears at high flow rates. In a trapezoidal channel, this geometrical symmetry in secondary flow pattern is broken and, as a result, convective mixing is enhanced moreover. The results of numerical simulations by the fluid particle tracer method agreed with mixing patterns obtained in experiments. An extended Danckwerts' intensity of segregation was applied to evaluate quantitatively the mixing pattern of intersection points of fluid particles with the conduit's cross-section. This index also showed higher mixedness in a trapezoidal channel than in a rectangular one.
The polymer electrolyte fuel cell (PEFC) is a promising candidate for mobile and vehicle applications and distributed power systems due to its high power density and low operation temperature. However, water flooding in the cathode gas diffusion layer (GDL) is one of the critical barriers to high performance operation, because liquid water condensed in the porous GDL blocks oxygen transport to the active reaction sites. In this study, we observed removal behavior of condensed water in a porous electrode of PEFC using a microscope and discuss its fundamental characteristics. Furthermore, in order to prevent water flooding and improve cell performance, a slit was introduced into the cathode GDL. With this cathode structure, it was found that water removal is promoted, and cell voltage and power density are increased at a high current density.