A theoretical study was made on the interstitial heat transfer coefficients in both consolidated and unconsolidated porous media. Firstly, a boundary layer consideration was introduced to consider heat transfer in unconsolidated porous media. A general Nusselt number correlation was derived using the boundary layer solution for the axisymmetric stagnation thermal boundary layer, which shows its square root dependence of the Reynolds number, and matches fairly well with existing experimental data and correlations. Then, for low-density consolidated porous media, a volume averaging theory was exploited to obtain the set of macroscopic energy equations. The energy equations along with mathematical modeling revealed the reason why the Reynolds number exponent of the Nusselt number expression for the case of low density consolidated porous media is much greater than that of unconsolidated porous media. The present expressions are compared against available experimental data and empirical correlations, and found to be valid for a wide range of the porosity and Reynolds number.
A two energy equation model based on the effective porosity concept has been introduced to attack the local thermal non-equilibrium problem of forced convection in a metal foam filled channel. Non-thermal equilibrium profiles of air and solid temperatures across the channel are sought solving the set of the energy equations in which both tortuosity and thermal dispersion neglected in most of previous analyses are properly and fully accounted for. Exact solutions are found, assuming a plug flow, for the two cases of thermally fully developed convective flows through a channel, namely, the case of isothermal hot and cold walls and the case of constant heat flux walls. The resulting temperature profiles across the channel for the case of metal foam and air combination reveals that the local thermal equilibrium assumption may hold for the case of isothermal walls, but, may fail for the case of constant heat flux walls. Thus, the two energy equation model must be used for such thermal problems.
After confirming that the tangent hyperbolic function THINC (tangent of hyperbola for interface capturing) is effective for transport of binary distribution, we proposed a new method in which the coefficient is adjusted according to the inclination of the interface in order to overcome the problems that occur in dealing with multi-dimensional problems. The new scheme was compared with the THINC scheme, the THINC/WLIC scheme, the Donor-Acceptor scheme and the Upwind scheme by carrying out advection tests with three kinds of shapes. The proposed scheme was able to significantly suppress shape errors and had good volume conservation. For the calculation of surface wetting behavior of a droplet, the volume conservation was excellent, and the droplet interface was captured within two cells. The rising velocity of a bubble calculated from the simulation was also found to agree well with experimental results reported in the literature. In addition to excellent volume conservation, the bubble interface was found to be maintained within two cells.
Power consumption was measured for a rectangular mixing vessel with a paddle impeller, pitched paddle impeller or Rushton turbine. Power number data of such vessels have hitherto not been published. It was found that the power numbers of a rectangular vessel with these impellers corresponded to those of a cylindrical vessel of diameter equal to the diagonal of the rectangular vessel and baffle of BW/D=0.1 and nB=1.
A benzene-permselective silica hybrid membrane was successfully prepared by counter-diffusion CVD using PrTMOS (propyltrimethoxysilane) and O3 as reactants. Deposition temperatures and O3 flow rates were important parameters. The H2/N2 permeance ratio was 250 through a membrane deposited at 240°C. The pore size of the membrane was estimated at about 0.3 nm from the kinetic diameter of H2 (0.29 nm) and N2 (0.36 nm). On the other hand, the N2/SF6 permeance ratio was 529 through a membrane deposited at 270°C. From the kinetic diameter of SF6 (0.55 nm), the pore size of membranes was estimated as 0.4–0.5 nm. Thus, the pore size of the membranes increased with increasing the deposition temperature up to 270°C. SF6 permeances were proportional to total fluxes of pervaporation (PV) tests. This can be explained by the similar kinetic diameters of benzene (0.58 nm) and SF6. The maximum benzene selectivity over cyclohexane was 113 with the total flux of 2.2×10-4 kg m-2 h-1 through the membrane deposited at 320°C at an O3 flow rate of 0.4 L min-1.
The Antoine constants and the NRTL parameters were determined for a system of water+propyleneglycol monomethyl ether (PGME)+propyleneglycol monomethyl ether acetate (PGMEA) using automatic vapor–liquid equilibrium measuring equipment. First, the NRTL parameters of a methanol+ethanol+water system and an acetone+methanol+water system were determined using the equipment. With these parameters, a distillate curve map was plotted to trace the vapor phase compositions of the residual curve map calculations, and this map was compared with the distillate trajectory of batch distillation. For the system of water+PGME+PGMEA, the distillate trajectory of batch distillation was examined by drawing the distillate curve map for the case in which the distillate in the region of liquid-liquid equilibrium was divided into two phases and the oil phase was returned to the still. These studies showed the possibility of evaluating batch distillation for systems with unknown physical properties using this equipment and the distillate curve map.
The crossflow microfiltration process with vibration was experimentally investigated with lard/phosphate- buffered saline emulsion containing PMMA particles. This emulsion was used as a model sample for filtration washing and concentrating mononuclear cells in bone marrow in the case of the regenerative liver therapy. The experimental results showed that the use of vibration on a filter was effective to maintain a high filtration flux of the oil in water emulsion containing solid particles. Excessive vibration resulted in a compact cake structure, leading to a decrease in filtration flux. For a quasi-steady state filtration rate, optimum operational conditions were found to exist in the range of this experiment.
Initially, a boundary-layer development around a heated solid surface is laminar in natural convection, but at some critical distance from the leading edge, depending on the flow field and the thermo-physical properties, small disturbances in the flow begin to be amplified, and a transition process takes place until the flow becomes turbulent. In this transition region, the heat transfer and fluid flow of natural convection have not necessarily been elucidated. The present study therefore focused on natural convection along a vertical smooth flat plate uniformly heated under steady-state conditions to investigate the characteristic phenomena of the transition region. The two-dimensional temperature field was visualized by infrared tomography and analyzed using an image processing technique to acquire time series data for statistical analyses applying fast Fourier Transfer and Wavelet transfer. A series of visualizations and signal analyses revealed the possibility of characteristic temperature patterns (pseudo-horseshoe-shaped temperature patterns) in the transition region. It was also clarified that fluctuation components with comparatively short and long cycles are contained simultaneously in the fluctuating temperature that appears in the transition region. Periodic fluctuation that can be explained by a linear stable theory takes place until the flow becomes turbulent, and disappears with development of the turbulent flow.
A process simulator was developed for the synthesis of bio-propylene from bio-ethanol with a zeolite catalyst by determining the reaction mechanism and the reaction rate constants that simulate the experimental data. The reaction mechanism thus determined consisted of 28 reactions involving 16 chemical species. The values of the reaction rate constants (the frequency factors and the activated energies) were determined by use of a genetic algorithm to solve the non-linear optimization problem of minimizing the differences between the simulated values and the experimental data. As a result, the behavior of experimental data, especially for the major species such as propylene and ethylene, was well explained by the output of the simulator developed in this work. Therefore, the simulator should be useful for optimizing the design and the operation of reactor in this process.
In this report, bisphenol A (BPA) was selected as a model xenobiotic compound in soil slurry, and the bioremoval of BPA by white rot fungi in shaking flask, roller bottle reactor and bubble column reactor were studied. The initial weight ratio of liquid and soil over some level is found to be necessary to form soil slurry. The threshold of the ratio for soil slurry forming seems to be the maximum moisture content of soil. In shaking flask, the removal ratio of BPA was 0.97 (n=2) in 24 h. The period for achieving this ratio was shortened about 30 times in comparison to our previous experiment in solid state. In case that the soil slurry was observed in shaking flask, the removal ratios of BPA at 24 h were constant (0.98±0.01) and independent to shaking speeds (60, 100 rpm). The roller bottle reactor could achieve effective bioremoval reaction in lower rotation speed comparing with shaking flask, and the removal ratio reached almost 1 at 12 h. In bubble column reactor, the differences in BPA removal rates were observed among bubble columns with different shape. The shape of reactor seems to affect the mixing state of soil slurry rather than oxygen supply.
Nanoparticles of ZnO and TiO2 were supported in large quantities on the surface of cotton fibers wrinkled by treatment with supercritical CO2 and water. Nanoparticles of ZnO and TiO2 were deposited onto treated and untreated cotton fibers by an immersion method. The condition of nanoparticles supported on the surface of the fibers was observed by SEM, and the amounts of ZnO and TiO2 supported were quantified by EMPA analysis. The results showed that the cotton fibers treated with supercritical CO2 and water supported far larger quantities of ZnO and TiO2 than the untreated cotton fibers. The amounts of ZnO and TiO2 supported increased with the degree of wrinkling generated on the surface of the treated cotton fibers, and the highest amounts were supported when the fibers were treated with supercritical CO2 and water at 20 MPa and 80°C for 1 h. The cotton fibers supporting nanoparticles were tested for the antibacterial effects of ZnO and whiteness of TiO2. The treated fibers were found to have higher bacteriostatic activity and a higher degree of whiteness than the untreated fibers, and these properties were unaffected by rinsing the fibers in water.
The effect of prebake (PB) temperature on chemical structure and removal by wet ozone of the photo-active compound (PAC) positive-tone novolak resin/diazonaphthoquinone by use of FT-IR, micro-sampling mass spectrometry (μ-MS) and thermogravimetry analyzer (TGA). Resist films prebaked at between 100˚C and 200˚C were completely removable by wet ozone, but the resist removal rate decreased with increasing PB temperature and decreased significantly between 140˚C and 160˚C. The FT-IR spectrum revealed desorption of N2 from the PAC near the PB temperature of 160˚C. On the other hand, the novolak resin did not change with PB temperature. The μ-MS results confirmed that the decomposition temperature of the novolak resin and PAC did not change with changes in PB temperature. TGA curves indicated that the amount of the solvent remaining in the resist film was substantially desorbed at PB temperatures between 140˚C and 160˚C. From these results, we concluded that the chemical structure and thermal cross-linking of the resist are not affected by changes in the PB temperature. In contrast, the evaporation of residual solvents in the resist film increases with increasing PB temperature, resulting in shrinkage of the film. The decrease in resist removal rate of about 60% between 140˚C and 160˚C was therefore concluded to be due to the curing of the film.
Electro-oxidation of ethanol on a PtRu/C catalyst at intermediate temperature (250°C) was investigated by electrochemical measurement and analysis of reaction products using cesium dihydrogen phosphate as a proton-conducting electrolyte. High CO2 selectivity in the ethanol electro-oxidation was observed, which suggests that total oxidation of ethanol proceeds effectively at the intermediate temperature. Formation of CH4, a major byproduct in ethanol electro-oxidation on Pt/C catalyst at intermediate temperature, was suppressed by Ru addition, while CH3CHO formation was accelerated by Ru addition. Detailed kinetic analysis of the electrode reaction mechanism revealed that Ru addition accelerates ethanol dehydrogenation and water dissociation in ethanol electro-oxidation. Furthermore, OH formed in the fast water dissociation enhances oxidation of surface C1 adsorbates, which are produced in fast C–C bond dissociation of ethanol on Pt at intermediate temperature. These results suggest the effectiveness of Ru addition in aiming for the total oxidation of ethanol at intermediate temperature.
Cerium oxide abrasive is widely used in fine polishing processes, such as fabrication of lenses, prisms, liquid crystal panels, and glass substrates for hard disks. More than 90 percent of rare-earth metals, including cerium, have been imported from China, but because of China’s recent resource strategy, their price has risen dramatically. Reuse and recycling are, therefore, urgently required. Recovery technologies of cerium oxide abrasive particulates from used abrasive slurry were examined. The particles in used slurry were too small for separation by natural sedimentation. We have discovered that secondary particles were formed by freezing and thawing the slurry, and that the sediment and supernatant liquid were easily separated. This technique requires only a freezer, and does not employ flocculants or other chemicals. Freezing and thawing separation is an effective method of recovering the abrasive particulates in used slurry.
Three-way catalysts containing precious metals such as platinum are used for purification of exhaust gas from gasoline-fueled automobiles, but because of rising demand and soaring prices for precious metals, it is necessary to develop alternative catalysts with comparable properties. This study examined the synthesis of an electrical heating alumite plate catalyst containing cerium, iron, and carbon and its properties in exhaust purification. The catalyst was synthesized by impregnation using an organometallic solution of cerium tartrate and iron ammonium citrate and by vapor-phase treatment with carbon monoxide. The electrically heated alumite plate catalyst containing cerium, iron and carbon was found to have excellent properties for purification of automobile exhaust gas.