جستجوی مقالات مرتبط با کلیدواژه « کشش سطحی » در نشریات گروه « شیمی »

Keeping constant and reasonable production from oil reservoirs which are in the second half of their life has pushed scientists to consider enhanced oil recovery (EOR) methods and novel methods in this field are presented. Magnetized water flooding as a green and compatible method with the environment is one of the novel methods besides polymer flooding which has been applied many years ago. The main purpose of this paper is to combine the two mentioned methods to increase the efficiency of flooding operations. Therefore, magnetized water is utilized as a solvent for polymer powder, then surface phenomena including interfacial tension and contact angle were studied. Somehow the effects of four factors including; magnetization time, magnetic field intensity, time after magnetization, and polymer concentration on mentioned surface phenomena were evaluated. The results showed that all of the aforementioned factors except magnetization time have a great impact on interfacial tension and just magnetic field intensity has a significant effect on contact angle. These results prove that flooding of magnetized water-based polymer solution has a great impact not only on macroscopic efficiency but also on microscopic efficiency and can improve the efficiency of polymer flooding.

In this study, gas phase holdup in a gas-liquid bubble column reactor was experimentally studied. To conduct experiments, a bubble column with a height of 54 cm and a diameter of 10.4 cm was applied. The studied systems include water-air, Gasoline-air, and Behran oil-air. Experiments were carried out in the range of 400-50 rpm agitator. Based on the Buckingham π theorem, a semi-experimental model for gas phase holdup was presented. The results showed that with increasing viscosity from 0.001 to 0.0136 gas phase holdup loss due to high adhesion of bubbles at high viscosity and also the increase of bubble size at the output from the distributor decreases from 0.41 to 0.333. Among the selected systems, the gas phase holdup of the gas-air system was maximized. The results also showed that in materials with low viscosity, the gas phase reduction was due to the formation of liquid vortex movement and air canalization by the agitator. The best agitator speed to increase the gas phase holdup at water and oil are 150 and 400 rpm, respectively.

It is well known that asphaltene molecules play a significant role in stabilizing the emulsion of water and oil. Molecular dynamics simulation was employed to investigate the aggregation and orientation behaviors of asphaltene molecules in a vacuum, toluene, and water interface. It was found that the simulation results have a good agreement with available data. In order to investigate the effect of asphaltene structures on the self-assembled behavior of them, six different types of asphaltene structures are selected which are different in the terms of molecular weight, carbon-chain size, and heteroatoms in the asphaltene structure. At first, the behavior of asphaltene molecules was studied purely and it was found that the hydrogen bond plays a significant role in asphaltene molecule aggregation. In addition, the interfacial tension results show that the presence of OH and NH groups, as well as hetero atoms in the asphaltene molecules, cause they have hydrogen bonding with water molecules, so the interfacial tension compare to the pure toluene reduces. But on the other hand, if the asphaltene molecules do not have any O and N atoms, they have little tendency to be present at the water surface and they were dispersed inside the toluene solvent.

The aim of this study is simulating a system of water-GNPs and investigating nanofluid specifications and heat transfer proses from nanoparticles to solution. The initial condition is coordinated by the use of Packmol and Moltemplate codes, General equations were applied by the use of LAMMPS open-source code. Post-Processing methods were down by the use of MATLAB, VMD and Python software. Heat transfer proses from GNPs to solution investigated by the use of SNEMD method. According to the result, adding GNPs reduces the interface layer and increases surface tension value. The rate of surface tension and mole fraction enhancement with the bigger GNPs is greater than the system with smaller GNPs. In cooling proses, the heat transfers fewer than 5ps in 2mm and heat conduction in the first layer of water is 50 greater than other parts of the fluid. It can be concluded that, when the molecular density increases near the surface of Nanofluid, and reduction of surface tension, Nanofluids dispersion with organic fluid is less possible. This phenomenon helps to increase the diagnosis and treatment efficiency. Therefore, by the use of GNPs in Hyperthermia, Increasing temperature has higher impacts on cancer cells closer to GNPs than far normal cells.

In this study, the surface tension and surface coordination number of the molten metal using the Stephen equation calculated and reported. Parameters such as enthalpy of vaporization, density and surface tension of the parameters are required. Assumptions to predict the surface tension of molten metals such as minor changes in the volume of melting point similar to the melting point of the crystalline structure of liquid and solid, considering the increasing entropy, and no matter particles interact with particles in the second and third layers the surface is used. Results have shown that the surface coordination number of molten metal is in the range of 0.3 -0.7 of bulk coordination number. As well as being dependent surface coordination number on different parameters, such as temperature and lack of uniformity in terms of the calculation of various metals has made it difficult to compare the surface coordination number numbers. Also, different equations have been used to correlate the coordination number and adjustable parameters reported.

In this paper, surface tension and surface properties of binary mixtures containing alcohol (methanol and ethanol) ionic liquid (1-bptf, 1-b-3-mptf and 1-b-4-mptf)) have been determined using thermodynamics and theoretical methods at various temperatures (293.15-323.15) K. First, the surface tension and the surface tension deviation data over the whole mole fraction range are correlated by thermodynamic based models: Fu et al. (FLW) and Myers-Scott (MS), respectively, and then a new approach, the interaction energy between alcohol and ionic liquid (U12) has been calculated with the results of FLW model. The results show that at fixed temperatures in each system, the value of U21 increased by increasing the size of the ionic liquid cation. Second, the surface tension was predicted by using artificial neural network (ANN) method and the results were compared with thermodynamics method. On comparing the computed values of surface tension (by three methods of FLW, MS and ANN) with experimental data, satisfactory results have been observed (the mean relative standard deviations obtained from the comparison are less than 3.5%). However, among the applied methods, ANN shows the best agreement between the experimental and predicted data because it finds the best nonlinear relationship between the mole fraction and either surface tension or surface tension deviation. The results of this study provide useful information on the component interactions in the surface and the bulk phases.

In this paper, a new mixing rule for predicting the surface tension of liquid mixtures is presented. The resulting equation is provided by a combination of Gibbs- Vollmer relation and NRTL activity coefficient model. The proposed model accurately predicts the surface tension of aqueous and non-aqueous solutions in a wide range of concentration. In order to evaluate the ability of this model, several surface tension of binary liquid systems were measured tensiometer (Kruss K20 Easy Dyne). The experimental data available in the literature also were used to prove the accuracy of the model. The results showed that the proposed model can predict accurately the experimental data in a wide range of concentration. Data of non-aqueous solutions were predicted with high precision as absolute average error of less than 1% was achieved for most of these systems. For aqueous systems with a high degree of non-ideality the deviation from experimental data is higher than other systems (up to 10%). This error occurred because the molecules with strong hydrogen bonds that can form a complex non-ideal mixture, even the use of accurate activity coefficient model could not eliminate completely the error. However, the model predictions are satisfactory and acceptable.

In this research، surface tension and surface properties of binary mixtures of water with a series of aliphatic carboxylic acids (C1-C4) were investigated by different models at temperature range between (288. 15 and 328. 15) K. Correlating of the surface tension of the above mentioned binary systems was performed with empirical and thermodynamic based models. In the present work، for the surface tension correlation we used the following models: Redlich-Kister (RK)، Li et al. (LWW)، Fu et al. (FLW) and Myers-Scott (MS). In addition to finding more information about the surface structure of binary mixtures، surface mole fraction was calculated using an extended Langmuir model (EL). The results provide information on the molecular interactions between the unlike molecules that exist at the surface and the bulk.

The enhanced oil recovery from oil wet carbonate rocks using wettability alteration mechanism by surface active compounds was investigated. The imbibition tests were done by two typical anionic and cationic surfactants, sodium dodecyl sulfate and hexadecyltrimethylammonium bromide, respectively. The experiments were carried out at one of the Iranian oil reservoir condition. The efficiency of oil recovery by anionic surfactant was approximately equal to brine imbibition at reservoir condition. The results showed that the cationic surfactants have the high potential for enhanced oil recovery by spontaneous imbibition.

In this research, biosurfactant production (surfactin) by Bacillus subtilis NLIM 0110 has been investigated. This microorganism was isolated from agricultural area of Iran. For surfactin production, the best condition of biosurfactant in shake flask was obtained at 37°C and 250 rpm. In this condition, maximum production of biomass and biosurfactant are 4 and 1.8 g/L. The yield of biosurfactant on biomass (Yp/x), biosurfactant on sucrose (Yp/s), and the volumetric production rate (Y) for shake flask were obtained about 0.45 g/g, 0.18 g/g, and 0.03 g/L.h, respectively. For this microorganism, the production of biosurfactant was proportional to the cell growth representing biosurfactant as a growth-associated product. The produced surfactin showed good surface activity because it is able to reduce the surface tension from 72 mN/m to 25 mN/m. Therefore, the proposed biosurfactant is appropriate candidate for industrial applications.

Rhamnolipids are among the best known biosurfactants and have been proven to be very promising in enhanced oil recovery, cosmetics, food and pharmaceutics. In this research, rhamnolipid production by Pseudomonas aeruginosa NP2 in a bioreactor
has been investigated. This study shows that the Pseudomonas aeruginosa NP2 is able to produce high quantities of rhamnolipid during 2.5 L batch bioreactor cultivations with sunflower oil as sole carbon source. The results showed that the maximum rhamnolipid concentration obtained was 13.5 g/L after 80 h of cultivation. The results also showed that the rhamnolipid production started at exponential growth phase and continued during the stationary phase. Two rhamnolipids, RL1 and RL, produced by the microorganism, were confirmed by TLC and HPLC analysis. Finally, the produced rhamnolipid showed good surface activity because it is able to reduce the surface tension from 68 mN/m to 26 mN/m. Thus, Pseudomonas aeruginosa NP2 could be an appropriate model for rhamnolipid production in pilot plant bioreactor systems.