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11.
The permeabilities of microscale fibrous porous media were calculated using the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM). Two models of the microscale fibrous porous media were constructed based on overlapping fibers (simple cubic, body-centered cubic). Arranging the fibers in skew positions yielded two additional models comprising non-overlapping fibers (skewed simple cubic, skewed body-centered cubic). As the fiber diameter increased, the fibers acted as granular inclusions. The effects of the overlapping fibers on the media permeability were investigated. The overlapping fibers yielded permeability values that were a factor of 2.5 larger than those obtained from non-overlapping fibers, but the effects of the fiber arrangement were negligible. Two correlations were obtained for the overlapping and non-overlapping fiber models, respectively. The effects of the rarefaction and slip flow are also discussed. As the Knudsen number increased, the dimensionless permeability increased; however, the increase differed depending on the fiber arrangement. In the slip flow regime, the fiber arrangement inside the porous media became an important factor. 相似文献
12.
E.J. Gutiérrez-Castañeda A. Salinas-Rodríguez 《Journal of magnetism and magnetic materials》2011,323(20):2524-2530
The effects of annealing prior to cold rolling on the microstructure, magnetic and mechanical properties of low-C grain non-oriented (GNO) electrical steels have been investigated. The grain structure of hot-rolled electrical steel strips is modified by annealing at temperatures between 700 and 1050 °C. Annealing at temperatures less than the ferrite to austenite+ferrite transformation temperature on heating (Ac1) causes a marginal effect on the grain size. However, annealing in the intercritical region at temperatures between Ac1 and Ac3 (the ferrite+austenite to austenite transformation temperature on heating) causes rapid decarburization and development of large columnar ferrite grains free of carbide particles. This microstructure leads, after cold rolling and a fast annealing treatment, to carbide free, large ferrite grain microstructures with magnetic and mechanical properties superior to those observed typically in the same steel in the industrially fully processed condition. These results are attributed to the increment in grain size and to the {1 0 0} fiber texture developed during the final annealing at temperatures up to 850 °C. Annealing at higher temperatures, T>Ac3, results in a strong {1 1 1} fiber texture and an increase of the quantity of second phase particles present in the microstructure, which lead to a negative effect on the final properties. The results suggest that annealing prior to cold rolling offers an attractive alternative processing route for the manufacture of fully processed low C GNO electrical steels strips. 相似文献
13.
Ismayadi Ismail Mansor Hashim Khamirul Amin Matori Rosidah AliasJumiah Hassan 《Journal of magnetism and magnetic materials》2011,323(11):1470-1476
Ni0.5Zn0.5Fe2O4 has been synthesized using mechanical alloying method with two variables (milling time and ball-to-powder weight ratio (BPR)) were varied in order to study its effect on the magnetic properties of the material. The effects of these two variables were studied using XRD, SEM, TEM and later by impedance analyzer with the frequency range from 1 MHz to 1.8 GHz. The results obtained however show that there are no significant trends to relate the milling time and BPR with the permeability and losses of the material studied. After being sintered at 1150 °C, all the effects of alloying process seem to diminish. 相似文献
14.
Kh. Gheisari S. JavadpourH. Shokrollahi B. Hashemi 《Journal of magnetism and magnetic materials》2008
Ferromagnetic powders which are surrounded by an electrically insulating film (soft magnetic composites (SMCs)) exhibit unique magnetic properties, such as relatively low magnetic losses and 3D isotropic magnetic behavior. In some electromagnetic applications, including microwave frequency range applications, it is necessary to increase electrical resistivity without any noticeable reduction in magnetic properties. To achieve this purpose, electrically resistant materials, for example, ferrites with acceptable magnetic properties, are suitable candidates. This paper focuses on the effects of the synthesized Ni–Zn ferrite addition on the magnetic properties of the SMCs containing Ni–Zn ferrite within iron particles. The structure was studied by means of X-ray diffraction (XRD). The microstructure and the powder morphology were examined by the use of scanning electron microscopy (SEM). The magnetic measurements on powders and samples were carried out using a vibrating sample magnetometer (VSM) and an LCR meter, respectively. The results indicate that the lowest magnetic loss and the highest magnetic permeability are related to the composites with 20 wt% ferrite and 2 wt% ferrite, respectively. Also, the composites with 10 wt% ferrite show a good combination of magnetic loss and magnetic permeability in the range 0–500 kHz. 相似文献
15.
Sequestration of carbon dioxide in geological formations is an alternative way of managing extra carbon. Although there are
a number of mathematical modeling studies related to this subject, experimental studies are limited and most studies focus
on injection into sandstone reservoirs as opposed to carbonate ones. This study describes a fully coupled geochemical compositional
equation-of-state compositional simulator (STARS) for the simulation of CO2 storage in saline aquifers. STARS models physical phenomena including (1) thermodynamics of sub- and supercritical CO2, and PVT properties of mixtures of CO2 with other fluids, including (saline) water; (2) fluid mechanics of single and multiphase flow when CO2 is injected into aquifers; (3) coupled hydrochemical effects due to interactions between CO2, reservoir fluids, and primary mineral assemblages; and (4) coupled hydromechanical effects, such as porosity and permeability
change due to the aforementioned blocking of pores by carbonate particles and increased fluid pressures from CO2 injection. Matching computerized tomography monitored laboratory experiments showed the uses of the simulation model. In
the simulations dissolution and deposition of calcite as well as adsorption of CO2 that showed the migration of CO2 and the dissociation of CO2 into HCO3 and its subsequent conversion into carbonate minerals were considered. It was observed that solubility and hydrodynamic storage
of CO2 is larger compared to mineral trapping. 相似文献
16.
Smoothed Particle Hydrodynamics Modeling of Transverse Flow in Randomly Aligned Fibrous Porous Media
The Lagrangian smoothed particle hydrodynamics (SPH) method is employed to obtain a meso-/micro-scopic pore-scale insight
into the transverse flow across the randomly aligned fibrous porous media in a 2D domain. Fluid is driven by an external body
force, and a square domain with periodic boundary conditions imposed at both the streamwise and transverse flow direction
is assumed. The porous matrix is established by randomly embedding a certain number of fibers in the square domain. Fibers
are represented by position-fixed SPH particles, which exert viscous forces upon, and contribute to the density variations
of, the nearby fluid particles. An additional repulsive force, similar in form to the 12-6 Lennard-Jones potential between
atoms, is introduced to consider the no-penetrating restraint prescribed by the solid pore structure. This force is initiated
from the fixed solid material particle and may act on its neighboring moving fluid particles. Fluid flow is visualized by
plotting the local velocity vector field; the meandering fluid flow around the porous microstructures always follow the paths
of least resistance. The simulated steady-state flow field is further used to calculate the macroscopic permeability. The
dimensionless permeability (normalized by the squared characteristic dimension of the fiber cross section) exhibits an exponential
dependence on the porosity within the intermediate porosity range, and the derived dimensionless permeability—porosity relation
is found to have only minor dependence on either the relative arrangement condition among fibers or the fiber cross section
(shape or area). 相似文献
17.
Mark G. Jones Kenneth C. Williams 《Particuology》2008,6(5):289-300
An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows: fluidised dense phase and plug flow, and dilute phase oniy. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined: basic particle parameter based (e.g. particle size and density) and air-particle parameter based (e.g. permeability and de-aeration). The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment. 相似文献
18.
Egor I. Trilisky Harun Koku Kirk J. Czymmek Abraham M. Lenhoff 《Journal of chromatography. A》2009,1216(36):6365-6376
Commercially available polymer-based monolithic and perfusive stationary phases were evaluated for their applicability in chromatography of biologics. Information on bed geometry, including that from electron microscopy (EM), was used to interpret and predict accessible volumes, binding capacities, and pressure drops. For preparative purification of biologics up to at least 7 nm in diameter, monoliths and perfusive resins are inferior to conventional stationary phases due to their low binding capacities (20–30 g/L for BSA). For larger biologics, up to several hundred nanometers in diameter, calculations from EM images predict a potential increase in binding capacity to nearly 100 g/L. The accessible volume for adenovirus calculated from the EM images matched the experimental value. While the pores of perfusive resins are essentially inaccessible to adenovirus under binding conditions, under non-adsorbing conditions the accessible intrabead porosity is almost as large as the interbead porosity. Modeling of breakthrough curves showed that the experimentally observed slow approach to full saturation can be explained by the distribution of pore sizes. 相似文献
19.
Maria K. Daletou Joannis K. Kallitsis George Voyiatzis Stylianos G. Neophytides 《Journal of membrane science》2009
The interaction of steam with phosphoric acid imbibed electrolyte composed of PBI/PPy(50)coPSF 50/50 polymer blend and its effect on fuel cell performance was studied regarding its permeability through and its chemical interaction with the membrane. It was found that steam is the only gas that permeates the membrane with a permeability coefficient 1.1 × 10−14 mol cm cm−2 s−1 Pa−1 at 150 °C. This is attributed either to the high solubility of water in phosphoric acid or to the chemical interaction with pyrophosphoric acid. The latter was demonstrated by carrying out TGA experiments under various water vapor partial pressures. Water reacts with pyrophosphoric acid in order to maintain the equilibrium concentration of phosphoric acid at high level, thus improving proton conductivity and fuel cell performance. In addition it is shown that excess water dissolves in the membrane thus maintaining the “membrane/acid” system at high hydration level. This depends both on temperature and steam partial pressure. Although in the present study it is shown that steam plays a significant role in the performance of the high temperature Polymer electrolyte membrane (PEM) fuel cell, nevertheless its feed with humidified gases is not necessary, due to the back transport of the water produced at the cathode. 相似文献
20.
《Physics letters. A》2014,378(30-31):2308-2311