جستجوی مقالات مرتبط با کلیدواژه « میان متخلخل » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Emulsifying porous polymers have many pharmaceutical and industrial applications and are considered as new materials for separation. In this research, first the emulsion synthesis of poly (styrene-di vinylbenzene) was performed and then the effect of increasing the functional group of sodium styrene sulfonic acid on the hydrophilicity of the emulsion porous polymer poly (styrene-divinylbenzene) was investigated. Scanning Electron Microscope to study surface morphology and determine the size distribution of surface cavities and Energy Dispersive X-ray analysis test to investigate the presence of sulfur and sodium atoms in the surface of functionalized porous polymer and contact angle measuring device with Coupled-Camera Devise(CCD) and with software for measuring the contact angle of droplet contact with the surface to evaluate the hydrophilicity of the surface of polymerized emulsion polymer poly (styrene-divinylbenzene) were used. Increasing sodium styrene sulfonic acid has no effect on the shape and size of the cavities formed, but the hydrophilicity of the samples increased with increasing sulfone factor in the aqueous phase and the appropriate percentage of sodium styrene sulfonic acid in the aqueous phase was about 2%. With an increase of more than 2%, a slight increase in the hydrophilicity of the surface of the emulsion porous polymer poly (styrene-divinylbenzene) was activated and the graph became almost flat with slope changes insignificant.

This study addresses the numerical simulation of cohesive crack propagation and the problem of normal contact in porous media. Penalty method is used to inforce essential boundary conditions. The strong discontinuity in the deformation field is effectively modeled by exploiting the partition of unity property of element-free Galerkin shape functions and employing an external enrichment strategy. To account for the crack initiation and propagation behavior in mode I, which occurs under tensile stresses, as well as the compressive behavior at the edges of a closed crack in compression, the cohesive crack theory and the penalty method are incorporated into the existing computer program prepared for the simulation of porous media using the enriched element-free Galerkin method. The resulting algebraic system of equations are strongly non-linear. So, a suitable approach must be utilized to linearize and solve the equations. Newton-Raphson technique is utilized in this study for this purpose. The results obtained from solving the problems of tensile cracks and cracks under compression (i.e., the contact of two crack edges) indicate the capabilities of the numerical formulation and the prepared computer program. Expanding the prepared numerical model allows for the modeling of crack growth problems in porous media in the presence of fluids, as seen in processes like hydraulic fracturing.

The aim of this study was to produce porous nanomaterials with a high specific surface area to increase the separation capacity of the cationic surfactant of cetyltrimethylammonium bromide (CTAB) from water. To this end,, meso and micro-porous carbon fiber / ZIF-8 nanocomposites were produced in situ without the use of surfactants by a simple and cost-effective method of sediment synthesis with superhydrophobicity and high specific surface area. Nanocomposite capacity analyzes were studied quantitatively and qualitatively by standard methods. According to the results, ZIF-8 particles with a crystal size of 27 nm and an average size of 30 to 50 nm were obtained. A rough surface with a ZIF-8 coating thickness of between 0.1-1 microns was obtained for carbon fiber / ZIF-8 nanocomposites. According to the research findings, the maximum adsorption of 388 mg / g for surfactant by fiber-carbon nanocomposite / ZIF-8 with a specific surface area of ​​260 m2 / g and the porosity of micropores and mesopores with an average size of 1.6 nm and 3/8 was obtained. Superhydrophobicity of carbon fiber nanocomposite / ZIF-8 with wettability angle with water of 150 ° and electrostatic collisions were identified as the dominant mechanisms of surfactant separation. The performance of the adsorbent in static and dynamic systems with the effect of different parameters was investigated in this study. The adsorption mechanism of the surfactant on the adsorbent was interpreted by the Langmuir adsorption isotherm model, and the first-order kinetics is the control mechanism of the adsorbent behavior over time.

Highly porous polymers are mainly produced by emulsion polymerization. In this study, first the emulsion synthesis of poly (styrene-divinylbenzene) was performed and then the effect of increasing the amount of salt in the aqueous phase on the structure of porous polymer was investigated. Scanning electron microscopy was used to study the surface morphology and determine the size distribution of surface cavities. The appropriate amount of aqueous phase to oil phase for emulsion polymerization and production of porous polymer is at least 75% and adding of one percent of salt in the aqueous phase caused more pores with smaller size on the surface of the porous polymer and by increasing the salt, pores with larger diameter and more uniform distribution were obtained. According to the purpose of the study, which was to create fine surface cavities, the appropriate sample in this field was a sample containing 1% salt with a ratio of water phase to oil phase of 75% to 25%, in which case more cavities with smaller size in two index sizes with distribution uniform and symmetrical scattering with PDI of about 1 with an average diameter of 5.21 μm was obtained.

Expanded surfaces are considered as the common way to heat transfer increment in the industry, but due to their operating conditions and lack of footprint, their use in some situations is limited. Because of its ability in thermal efficiency increment using increasing available area and change in velocity gradient, the porous medium has been considered as a novel solution in heat transfer increment. During this investigation the effective parameters on heat transfer (Nusselt number (Nu)) in the presence of porous medium (configuration, thermal conductivity, pore gradient, porosity, permeability and Darcy number (Da), thickness, fluid velocity, and heat source) were studied. The studied configurations can be classified in partial and fully porous categories. Among the investigated papers, the fully filled configuration usually has shown the maximum exchanged energy and pressure drop. Because using a porous medium leads to pressure drop increase, an index was reported to compare between different configuration can be applied. Finally, limitations and challenges in this field were investigated.

Hydrogen storage capacity of yttrium (Y)-decorated on porous graphene (PG) was examined through density functional theory calculations. PGs were selected considering topological symmetries. Our calculations show that the most stable locations for adsorption of Y are located on the center of carbon rings and the polarization and the hybridization mechanisms both contribute to the Y atom adsorption on PGs. Analysis of charge density difference demonstrated that the presence of Y could play an efficient role for stronger adsorption of hydrogen molecules rather than increasing pore sizes. Compared to H2 adsorption on graphene, injecting topological defect such as hexagon porous and decoration with a transition metal atom such as Y can effectively create much more conductive states at Fermi energy. A maximum of four hydrogen molecules can be adsorbed on
Y-PGs system. The highest average adsorption energy is related to porous graphene with larger pore size with average absorption energies of 0.513 eV.

Syngas, a mixture of hydrogen and carbon monoxide, is used as a valuable intermediate gas in important processes such as methanol, ethanol, ammonia, Fischer-Tropsch Synthesis as well as de-sulfurization units. Conventional industrial processes to produce syngas, such as steam reforming, demand high investments and are energy-consuming. Meanwhile, partial oxidation is an alternative method of syngas production with the advantage of lower H2/CO ratio. In the current work, a pilot scale syngas production by partial oxidation in a ceramic porous media is presented. The results obtained from the pilot show that a syngas with H2/CO ratio from 1.14 to 1.47 is produced. The product has lower carbon content than that of a reactor with a common burner. The remained methane, water and CO2 could be removed in the purification unit. According to the observation, when the flame is located upward in the burner, the final product is free of soot.

In an oil reservoirs, the mechanical stresses, the thermal stresses and the fluid pressures can effect on each other and create a completely coupled phenomenon. Reservoir deformations due to thermal and mechanical stresses can cause the changes on effective stress and effect on the rate of production. Similarly, fluid pore pressure and temperature variations can effect on the deformation of reservoirs. Since these phenomena are mutually interacting with each other, considering the effects of temperature, fluid pore pressure and deformation on reservoir production requires the simultaneous simulation of heat, geomechanical and flow equations. In this article, first, the history of thermo-hydro-mechanical modeling is described. Then, the governing equations include three sets of mass equilibrium, momentum equilibrium and energy balance equations are presented for a non-isothermal deformable porous medium that is saturated by three phases of water, oil, and gas. These equations are related to each other and are solved in the form of partial differential equations. Due to being coupled of governing equations and the complexity of their boundary conditions, this equation is usually solved numerically. Different numerical methods have been used for solving which have different positive and negative points. Finally, the numerical solution of coupled thermo-hydro-mechanical equations is described in a finite volume and finite element methods and the examples of porous media simulation are presented. The examples show the ability of the proposed model.

In this paper, the experimental and the numerical results of a porous media burner containing spherical alumina particles are investigated and also are compared with each other. Based on the data, the maximum production of hydrogen mole fraction and the maximum conversion rate of methane to hydrogen and carbon monoxide have been investigated. Moreover, the results show a good agreement between experimental and numerical methods. The optimum efficiency of the burner is calculated and shows that under good input conditions, the maximum hydrogen production can be achieved with a relatively optimal 75% energy efficiency. It has been shown that despite the significant effects of equivalence ratio on output characteristics parameters, which are considered by many researchers in their papers, other input parameters such as released energy, reactor size, particle diameter (porosity) and the permeability of medium are important and effective on the maximum production of hydrogen.

Membranes are thin layers that act as selective barriers to separate the components of materials and control the mass transfer between different phases. Therefore, their two main functions include: component selectivity and the permeability characteristics. Membranes according to their material sources are classified into four categories referred as polymeric, ceramic, metal and liquid types. Among these, polymeric membranes are the most favorable materials because of their availability in various chemical structures, their optimum physical properties and lower prices. Polymeric membranes are produced by four main methods known as solution casting, stretching, template leaching and track etching. Among them, stretching technique is inexpensive and because no solvent is used in this process, stretching method has lower environmental impacts. Among different polymers, polyolefines such as polyethylene (PE) and polypropylene (PP), due to their lower price, semi-crystallinity, good mechanical properties, chemical stability and easy process ability, are more appropriate for manufacturing of polymeric membranes by stretching method. Porous membranes are used in applications such as battery separators and drug delivery devices for controlling the permeation rate of chemical components. In this paper, we present some useful information on the above subject by reviewing the related published works in this area.

Fingering phenomena in porous media has a lot of applications and various models in industries and natural issues. Recently several studies have been done on the stability of fluid in porous media. In this paper, the nonlinear instability of viscous fingering in a homogenous porous media is studied. Using a Fourier spectral method as the basic scheme for numerical simulation, equations transferred to Fourier space. The effect of mobility ratio on mixing length, sweep efficiently and transversely average concentration is examined and results indicate that in a high mobility ratio, sweep efficiently decrease and mixing length increase. Also estimation on beginning of viscous fingering instability has been done by analyzing of mixing length›s graph. In this paper, a new finger interaction mechanism is reported for the first time and named trifurcated tip, other mechanisms reported by previous researcher in the case of high mobility ratio, all are observed in this paper. Also the development of the new finger structures is explained by examining the velocity field which is superposed on the concentration contour.

the porous media of oil reservoirs have different layers with wide range scales which are different from effective scale of fluid flow in reservoirs. To reduce the calculating time of porous reservoirs modeling, each physical effect should be treated separately on its scale and area of influence. In this paper, the capillary pressures parameters between fluid phases were added on a multiscale deformable model to increase the accuracy of modeling. So, the governing equation was revised and a homogeneous oil reservoir was analyzed considering capillary influences. Comparing the results of analyzing the homogeneous oil reservoir with or without capillary effect shows that the water pressure was increased around the injection point and was decreased around the production point after considering capillary. It seems that the effects of capillary pressures on fluid pressures was significant and should be considered especially in modeling of inhomogeneous reservoirs due to increasing the irregularity flowing.

Nowadays filtration process is increasingly used in various areas such as water purification, food industries, filtering the air dust and other separation applications. In this work, the HDPE microporous filters have been fabricated at different pressure and time conditions via sintering process and then were characterized by different techniques. It can be expected that microstructure and mechanical properties of the samples could be controlled by changing the fabrication parameters like temperature, pressure, time of the process and also by changing the properties of the resin such as powder shape, particle size and rheological properties. In the first step, by using DSC, MFI, rheology test and optical microscope, the most suitable polymeric powder for sintering process was chosen. The sintering temperature was fixed in the vicinity of melting temperature of the used HDPE powder, based on DSC result. In order to evaluate mechanical properties and porosity of the samples, the results obtained from the shear punch test, acetone drop permeability, gas permeability, transition optical microscopy and SEM, have been used; then the effect of pressure and time parameters on the characteristics of the product has been studied. Finally, it was concluded that it is possible to make microporous filters with suitable mechanical properties, using sintering process at controlled pressure and temperature conditions.It can be seen that by increasing time and pressure, on the one hand the mechanical properties of the products increase, and on the other hand, their porosity and the gas permeability of the vents decrease.

The reduction of laser reflectivity is important as an effective defense to protect people and sensitive equipment. Reducing the reflectivity of surfaces is the most important strategy for decreasing the damages of laser radiation. In this research, the porous pigments are prepared to achieve the lowest percentage of reflection which were used to fabricate antireflective coatings for laser radiation. The porous carbon pigments containing CMK-1 and CMK-3 were prepared and the resulting black pigments were characterized using XRD, FE-SEM and DR-UV-Vis-NIR. The prepared paints were applied on aluminum substrate and the general tests of paints were investigated. The laser reflectivity was evaluated at wavelength of 532 nm that shows these coatings are effective antireflective coating for laser beam.

It’s possible to couple the EOR and nanotechnology to utilize the efficiency of both methods. This study is conducted in two steps, (1) experimental and (2) simulation. In the first stage of experimental section, a stable and uniform water-based solution of nano-sized particles of copper oxide with different concentrations (0.01 to 0.05 M) were prepared and then injected into the core samples. Then using a homemade apparatus, thermal conductivity of cores at different cases include dry core, water saturated, nano saturated and dried after one week was measured. The experimental results showed %25 and 6% enhancement of thermal conductivity of nano saturated and water saturated core, respectively relative to the dry core thermal conductivity. In the simulation section, the modeling domain was constructed with realistic morphology to represent cores’ structure. Structural details of cores are obtained by image processing of two captured images from thin sections of cores. The experimental data have been used and validations have been performed by comparing temperature difference variation along to the core for different cases. The simulation approach has been performed by solving heat transfer equations with a commercial finite element package (COMSOL™). The Simulation results of two used models show that the thermal conductivity of nano saturated models have 14% and 8% enhancement, respectively. The obtained results are consistent with experimental data and simulate the improvement of ETC after nanofluid injection. The present study demonstrates that computational fluid dynamics can be a reliable approach to confirm empirical data.

Titanium dioxide is used in many different fields, from industry to the area allocated to health and use of this materials to progress. Hence, reviewed synthesis and properties of porous titanium dioxide nanoparticles as a new and growing field is examined. Porous structure of titanium dioxide synthesized different methods for example, sol-gel and precipitation method. Also, The characterization of this type of nano-structures have been investigated.

Electrospinning as a simple method was used to produce cellulose acetate porous fibers. Motivation for production of fibers with small diameter in the submicron and nano scales was to achieve the material with a large surface area with porosity formation in the structure of electrospun fibers. In this study, porous cellulose acetate (CA) fibers were produced by electrospinning process from solution of CA/acetone/water. The porosity of the fiber was controlled by adjustment of the temperature and humidity of electrospinning chamber. Scanning electron microscopy (SEM) and densitometry were employed to evaluate the morphology and porosity of the samples. The results showed that the morphology and porosity of cellulose acetate fibers depend on the polymer solution concentration and relative humidity of electrospinning atmosphere. Cellulose acetate fibers were electrospun best at the concentrations of 12 to 18 wt% and relative humidity range of 40 to 80%. The highest porosity was obtained at the relative humidity of 80% and concentration of 15 wt%. In addition, by increasing the relative humidity of electrospinning environment and polymer concentration, the average diameter of the fibers was increased. With increasing the polymer concentration, there was less likelihood in thermodynamic instability and phase separation. In contrast, increases in relative humidity led to diffusion of more water into the electrospinning jet, giving rise to phase separation. Our observations revealed that the skin of fibers was formed at the earlier stage of the process and prevented the stretch in electrospinning jet.

Iran lies in tropical climate while global worldwide warming and subsequent draughts in recent several years intensified the notion of climatology, consequently optimal quality of urban and industrial water received more crucial considerations as though it is necessary to set more precaution over water consumption trends, meanwhile utilizing treated wastewater with eliciting convenient strategies for optimum consumption is sensible critically.The current paper represents two strategies by utilization of biofilm in solid surfaces (technology of biobarrier formation and trickling filter technology). Stepwise biofilm formation in these two areas is also explained and practical mathematical modeling in addition to present process employed is discussed in detail. The present paper reviews the employment of biofilm formation to upgrade the production of various industries such as petroleum, mineral, metallurgical, ceramic and hydrological facilities.The concept of biofilm, due to its increased growth of prostheses utilization in medical applications improves bacterial replication and colonies in body as though to threat the health & life even causing fatality, therefore the process of biofilm replication shall be manifested in positive and negative perspectives.