Journal articles: 'Diffusion. Mass transfer. Mixtures'

1

Tuchlenski, Axel, Oliver Schramm, and Andreas Seidel-Morgenstern. "Steady-State and Dynamic Mass Transfer of Gases in Porous Materials." Collection of Czechoslovak Chemical Communications 62, no. 7 (1997): 1043–56. http://dx.doi.org/10.1135/cccc19971043.

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The diffusion of binary gas mixtures through a porous asymmetric tubular membrane has been studied experimentally. A modified Wicke-Kallenbach diffusion cell consisting of two gas compartments separated by the membrane was used. Steady-state experiments with pure gases and binary mixtures were carried out in order to determine the transport parameters of the membrane with respect to the dusty gas model. To verify these parameters, the dynamic transport of binary mixtures was examined applying the dynamic diffusion cell technique proposed by Novak et al. The measured transients were in relative good agreement with the model predictions.

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D'yakonov, S. G., D. V. Proshchekal'nikov, G. S. D'yakonov, and R. A. Ibragimov. "Diffusional mass transfer in liquid mixtures." Journal of Engineering Physics 59, no. 6 (December 1990): 1611–18. http://dx.doi.org/10.1007/bf00870425.

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Meruyert, Beketayeva. "Numerical Calculation of the Diffusion Process in Multicomponent Hydrocarbon Gas Mixtures." International Journal of Mechanics 15 (May 25, 2021): 61–68. http://dx.doi.org/10.46300/9104.2021.15.7.

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Knowledge of the laws of diffusion is necessary in the description, design and calculation of the mass transfer process in the production, operation and transportation of gaseous fuels. In this article, the calculation of diffusion processes for five natural hydrocarbon gas mixtures into the air was carried out. The effective diffusion coefficients and matrix coefficients of multicomponent diffusion were determined. Also the advantages of using effective coefficients in the description of mass transfer were shown.

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Badr, O. A., and G. A. Karim. "Examination of the Formation of Combustible Mixtures by Diffusional Mass Transfer." Journal of Energy Resources Technology 111, no. 3 (September 1, 1989): 194–99. http://dx.doi.org/10.1115/1.3231423.

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The approximate prediction of the concentration profiles following the release of a fuel into air, typically within a confined space at constant pressure and temperature is presented using generalized charts based on the one-dimensional diffusion equation and an effective eddy diffusivity. It is suggested that such generalized plots can be employed to establish the size and changes with time of the associated flammable zones, including when convective diffusion may be involved. Examples for some typical common fuels are presented.

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Kossov, V. N., O. V. Fedorenko, V. Mukamedenkyzy, and A. Kalimov. "Special modes of diffusion mass transfer in isothermal triple gas mixtures." Journal of Physics: Conference Series 1565 (June 2020): 012061. http://dx.doi.org/10.1088/1742-6596/1565/1/012061.

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Duursma, Gail, Khellil Sefiane, and Joy Clarke. "Diffusion-Evaporation Studies of Binary Mixtures in Capillary Tubes." Defect and Diffusion Forum 273-276 (February 2008): 577–82. http://dx.doi.org/10.4028/www.scientific.net/ddf.273-276.577.

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Evaporation in restricted domains, e.g. in capillaries, is of industrial importance but is poorly understood. Where the evaporating liquid is a binary mixture, preferential evaporation of the more volatile component occurs initially and the evaporation rate is not constant, indeed it appears to occur in stages. Experiments of evaporation from the entrance of a capillary were performed for various binary mixtures of acetone and water and for pure liquids for comparison. Measurements of mass were taken over time for a range of capillary diameters from 0.6 mm to 2 mm. For simplicity, the experiments were performed with the meniscus “stationary” at the entrance of the tube, rather than allowing the meniscus to recede. The data were analysed and showed that, for the binary mixtures, the evaporation process had two distinct stages for the mixtures. The second stage always had a lower slope than the first, indicating a slower evaporation (similar multistage evaporation processes have been observed for sessile drops of binary mixtures). There are many phenomena at work in this process: surface evaporation; diffusion (or natural convective mass transfer) in the air beyond the capillary; diffusion in the binary mixture; circulation in the liquid; thermal effects of evaporative cooling. These are investigated, comparisons made and further studies are proposed.

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Tzan, Ying Liang, and Yu Min Yang. "Experimental Study of Surfactant Effects on Pool Boiling Heat Transfer." Journal of Heat Transfer 112, no. 1 (February 1, 1990): 207–12. http://dx.doi.org/10.1115/1.2910346.

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In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.

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Kandlikar, S. G. "Boiling Heat Transfer With Binary Mixtures: Part I—A Theoretical Model for Pool Boiling." Journal of Heat Transfer 120, no. 2 (May 1, 1998): 380–87. http://dx.doi.org/10.1115/1.2824260.

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Experimental evidence available in the literature indicates that the pool boiling heat transfer with binary mixtures is lower than the respective mole- or mass-fraction-averaged value. Although a few investigators have presented analytical work to model this phenomenon, empirical methods and correlations are used extensively. In the present work, a theoretical analysis is presented to estimate the mixture effects on heat transfer. The ideal heat transfer coefficient used currently in the literature to represent the pool boiling heat transfer in the absence of mass diffusion effects is based on empirical considerations, and has no theoretical basis. In the present work, a new pseudo-single component heat transfer coefficient is introduced to account for the mixture property effects more accurately. The liquid composition and the interface temperature at the interface of a growing bubble are predicted analytically and their effect on the heat transfer is estimated. The present model is compared with the theoretical model of Calus and Leonidopoulos (1974), and two empirical models, Calus and Rice (1972) and Fujita et al. (1996). The present model is able to predict the heat transfer coefficients and their trends in azeotrope forming mixtures (benzene/methanol, R-23/R-13 and R-22/R-12) as well as mixtures with widely varying boiling points (water/ethylene glycol and methanol/water).

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Mahmoud, Issa, Kenji Ishida, and Masanori Monde. "Analysis of ammonia vapor absorption into ammonia water mixtures: mass diffusion flux." Heat and Mass Transfer 41, no. 10 (June 8, 2005): 875–89. http://dx.doi.org/10.1007/s00231-004-0583-8.

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10

Kern, Ju¨rgen, and Peter Stephan. "Investigation of Decisive Mixture Effects in Nucleate Boiling of Binary Mixtures Using a Theoretical Model." Journal of Heat Transfer 125, no. 6 (November 19, 2003): 1116–22. http://dx.doi.org/10.1115/1.1622716.

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In the present paper an attempt is made to clarify the influence of mixture effects upon heat transfer in nucleate boiling of binary mixtures. The studies are based on a theoretical model that is briefly summarized. Evaluating heat and mass transfer around a single vapor bubble emphasizes a strong influence of the so-called micro region where the liquid-vapor phase interface approaches the wall. Due to the preferential evaporation of one component of the mixture, strong concentration gradients occur in the micro region. These microscale composition effects cause diffusive mass transfer, Marangoni convection, and a variation of the liquid-vapor phase equilibrium as well as a variation of the thermophysical properties. From a macroscopic point of view the bubble site density and the departure diameter vary with the composition of the liquid. By means of parameter studies decisive mixture effects are identified and their relevance in the nucleate boiling process is stated. The heat transfer coefficient crucially depends on the bubble site density and departure diameter. For increasing bubble site density, the influence of microscopic concentration gradients increases. But only the variation of liquid-vapor phase equilibrium becomes important, while diffusive mass transfer and Marangoni convection can be neglected.

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Oteuova, U. D., A. D. Alpeissova, М. К. Asembaeva, and A. Z. Nurmukhanova. "EFFECT OF VISCOSITY ON THE DIFFUSION MIXING PROCESS IN ISOTHERMAL MULTICOMPONENT GAS MIXTURES." BULLETIN Series of Physics & Mathematical Sciences 72, no. 4 (September 29, 2020): 156–61. http://dx.doi.org/10.51889/2020-4.1728-7901.24.

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In this article, the influence of viscosity on the stability of the diffusion process in isothermal multicomponent gas mixtures is experimentally studied. For gas systems 0,4300 C3H8 + 0,5700 He - 0,4300 C3H8 + 0,5700 CH4 and 0,4300 С3Н8 + 0,5700 Не - 0,4200 C3H8 + 0,5800 Ne, the results of calculating the number of partial losses of components at different pressures are given. The dependence of the amount of diffused components (partial expenses) on the pressure for this initial composition was studied. Then, the characteristic features of mass transfer for systems with different viscosities were compared over the same time intervals. Studies have shown a qualitative change in the nature of the mixing process. An increase in the viscosity of the mixture led to a stabilization of the diffusion process with an increase in the pressure in one case and the time of the process in the other. Analysis of the results showed that the viscosity affects the nature of the diffusion instability of the gas mixing process.

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12

Liao, Y., and K. Vierow. "A Generalized Diffusion Layer Model for Condensation of Vapor With Noncondensable Gases." Journal of Heat Transfer 129, no. 8 (September 11, 2006): 988–94. http://dx.doi.org/10.1115/1.2728907.

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The diffusion layer model for condensation heat transfer of vapor with noncondensable gases was originally derived on a molar basis and developed from an approximate formulation of mass diffusion, by neglecting the effect of variable vapor–gas mixture molecular weights across the diffusion layer on mass diffusion. This is valid for gases having a molecular weight close to that of the vapor or for low vapor mass transfer rates, but it may cause serious error if a large gradient in the gas concentration exists across the diffusion layer. The analysis herein shows that, from the kinetic theory of gases, Fick’s law of diffusion is more appropriately expressed on a mass basis than on a molar basis. Then a generalized diffusion layer model is derived on a mass basis with an exact formulation of mass diffusion. The generalized model considers the effect of variable mixture molecular weights across the diffusion layer on mass diffusion and fog formation effects on sensible heat. The new model outperforms the one developed by Peterson when comparing with a wide-ranging experimental database. Under certain limiting conditions, the generalized model reduces to the one developed by Peterson.

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Liu, Ming-Huei, Yu-Min Yang, and Jer-Ru Maa. "ON THE EXTENT OF THE MASS DIFFUSION EFFECT ON FILM BOILING HEAT TRANSFER IN BINARY MIXTURES." Numerical Heat Transfer, Part A: Applications 32, no. 8 (December 1997): 897–913. http://dx.doi.org/10.1080/10407789708913923.

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14

Kosov, V. N., S. A. Krasikov, O. V. Fedorenko, and A. B. Kalimov. "CONVECTIVE MIXING IN AN INCLINED CHANNEL CAUSED BY TERNARY DIFFUSION UNDER CONDITION OF INCREASING DENSITY OF THE MIXTURE WITH HEIGHT." BULLETIN Series of Physics & Mathematical Sciences 69, no. 1 (March 10, 2020): 224–30. http://dx.doi.org/10.51889/2020-1.1728-7901.39.

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Using methods of numerical simulation, we studied the quasi-stationary mass transfer of isothermal ternary gas mixtures in the vertical and inclined channels for the zone of flow exit from a given channel into the lower flask of a diffusion cell. Convective mixing is considered under conditions involving an increase in the density of the mixture with the height of the channel. The characteristic features of structured flows were studied at a certain content of the component with the highest molecular weight in the mixture. The convective formations in the vertical and inclined channels are compared. The dynamics of structured convective flows at various inclination angles is analysed. Estimates of the lifetime of a structural formation consisting mainly of the component with the highest molecular weight moving in a gas mixture with a lower density value are given.

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15

Hand, D. W., J. C. Crittenden, D. R. Hokanson, and J. L. Bulloch. "Predicting the performance of fixed-bed granular activated carbon adsorbers." Water Science and Technology 35, no. 7 (April 1, 1997): 235–41. http://dx.doi.org/10.2166/wst.1997.0282.

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Granular Activated Carbon (GAC) adsorption is an effective treatment technology for the removal of Synthetic Organic Chemicals (SOCs) from drinking water supplies. This treatment process can be expensive if not properly designed. Application of mathematical models is an attractive method to evaluate the impact of process variables on process design and performance. In this study, a mathematical modeling methodology incorporating the pore and surface diffusion model (PSDM) is proposed for known mixtures in fixed-bed adsorbers. Thermodynamic correlations for estimation of equilibrium parameters and empirical correlations for estimation of mass transfer parameters are presented. The PSDM was successfully compared to a 6-component mixture for empty bed contact times (EBCTs) of 2.4, 4.9, and 9.56 minutes.

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16

Kandlikar, S. G., and L. Alves. "Effects of Surface Tension and Binary Diffusion on Pool Boiling of Dilute Solutions: An Experimental Assessment." Journal of Heat Transfer 121, no. 2 (May 1, 1999): 488–93. http://dx.doi.org/10.1115/1.2826008.

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Pool boiling heat transfer with dilute binary mixtures introduces two additional effects due to binary diffusion, and due to change in the surface tension. The secondary effects due to changes in contact angle and wetting characteristics may also play a role. The present study focuses on identifying these effects for dilute aqueous solutions of ethylene glycol. Pool boiling experiments are conducted to generate data in the range of one to ten percent mass fraction. It is found that in the low concentration region, the binary diffusion effects are insignificant for aqueous solutions of ethylene glycol, and a slight improvement in heat transfer coefficient is observed over the pure water value. The binary diffusion effects are related to a volatility parameter, V1. The heat transfer coefficient does not degrade in the region where V1 < 0.03, and the surface tension does not change appreciably compared to pure water value. This points to the possibility that the changes in contact angle and wetting characteristics play an important role in the pool boiling heat transfer.

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17

Zheng, Sixu, and Daoyong Yang. "Determination of Individual Diffusion Coefficients of C3H8/n-C4H10/CO2/Heavy-Oil Systems at High Pressures and Elevated Temperatures by Dynamic Volume Analysis." SPE Journal 22, no. 03 (October 20, 2016): 799–816. http://dx.doi.org/10.2118/179618-pa.

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Summary By coupling heat and mass transfer for C3H8/n-C4H10/CO2/heavy-oil systems as well as by treating heavy oil as multiple pseudocomponents, a new technique together with its computational scheme has been developed to determine individual diffusion coefficients of alkane solvents and CO2 in heavy oil at high pressures and elevated temperatures by dynamic volume analysis (DVA). Experimentally, well-designed diffusion tests have been conducted for an n-C4H10/heavy-oil system, a CO2/heavy-oil system, an n-C4H10/CO2/heavy-oil system, and a C3H8/n-C4H10/CO2/heavy-oil system by using a visualized pressure/volume/temperature (PVT) setup. The volume change of liquid phase is monitored and recorded during the measurements, whereas the gas-chromatography (GC) method is used to determine the compositions of gas mixtures at the beginning and the end of the diffusion tests. Theoretically, the volume-translated Peng-Robinson (PR) equation of state (EOS) characterizing heavy oil as multiple pseudocomponents has been incorporated to develop a 2D heat-and-mass-transfer model for the aforementioned systems. The alternating-direction-implicit algorithm is applied to solve the 2D difference equations into which a moving gas/liquid interface has been successfully incorporated. The discrepancy between the measured and calculated dynamic-volume change and the discrepancy between the measured and calculated gas compositions at the end of diffusion tests have been minimized to determine the individual diffusion coefficients. Alkane solvents diffuse faster than CO2 in heavy oil, whereas addition of alkane solvent(s) into the CO2 stream not only enhances mass transfer, but also achieves an improved swelling effect of heavy oil. Among the four diffusion tests, the largest dynamic swelling factor at the end of the diffusion test is measured to be 1.118 for the C3H8/n-C4H10/CO2/heavy-oil system.

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Ezhov, V. K. "Distribution of the Diffusion Resistance to Mass Transfer Between the Liquid and Vapor Phases During Rectification of Mixtures." Atomic Energy 118, no. 4 (August 2015): 265–71. http://dx.doi.org/10.1007/s10512-015-9991-8.

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Absi, Rafik, Stéphane Marchandon, and Marc Lavarde. "Turbulent Diffusion of Suspended Particles: Analysis of the Turbulent Schmidt Number." Defect and Diffusion Forum 312-315 (April 2011): 794–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.794.

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For mass transfer applications, CFD codes need the turbulent Schmidt number . The aim of our study is the analysis of some theoretical closure results and analytical formulations for . We will investigate different formulations of from the basic conservation equations for sediment-water mixtures in turbulent open-channel flows based on a two-fluid description and a kinetic model. The kinetic model for turbulent two-phase flows provides which depends on particle Stokes number. Our study show that the two approaches provide that depends on turbulent kinetic energy (TKE), eddy viscosity and particles settling velocity. For the analysis, accurate analytical formulations for TKE and eddy viscosity calibrated by DNS data are presented.

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Ye, Yanghui, Cong Dong, Zhiguo Zhang, and Yangyang Liang. "Considering the Diffusive Effects of Cavitation in a Homogeneous Mixture Model." Processes 8, no. 6 (June 3, 2020): 662. http://dx.doi.org/10.3390/pr8060662.

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Homogeneous mixture models are widely used to predict the hydrodynamic cavitation. In this study, the constant-transfer coefficient model is implemented into a homogeneous cavitation model to predict the heat and mass diffusion. Modifications are made to the average bubble temperature and the Peclet number for thermal diffusivity in the constant-transfer coefficient model. The evolutions of a spherical bubble triggered by negative pressure pulse are simulated to evaluate the prediction of heat and mass diffusion by the homogeneous model. The evolutions of three bubbles inside a rectangular tube are simulated, which show good accuracy of the homogeneous model for multibubbles in stationary liquid.

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Ramos, Alex Martins, and Marco Aurélio Cremasco. "Equilibrium and mass transfer parameters estimation of the products of synthesis of piperonal by high performance liquid chromatography." Journal of Engineering and Exact Sciences 1, no. 1 (June 25, 2015): 01–15. http://dx.doi.org/10.18540/jcecvl1iss1pp01-15.

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The reaction sequences applied to essential oil of Piper hispidinervum D.C (long pepper) leads to formation of a multicomponent mixture composed, mainly, by piperonal, safrole, isosafrole and terpinolene. Due to importance of the piperonal for the pharmaceutical industry is that proposed separate it by high performance liquid chromatography. In this paper, it was studied the adsorption and mass transfer phenomena of these compounds using ethanol/water 70/30 (v/v) as mobile phase and C18 as stationary phase at 35 oC. Regarding to adsorption, the piperonal is the component that has the lowest affinity and terpinolene, the greatest with stationary phase. Regarding to mass transfer, effective diffusion and axial dispersion coefficients were around 10- (10 to 11) and 10- (7 to 8) m2.s-1, respectively. The internal resistance to mass transfer controls the overall mass transfer and parallel diffusion model describes the intra-particle transport mechanism.

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Agathonos, Pericles, and George Karaiskakis. "Measurement of activity coefficients, mass-transfer coefficients and diffusion coefficients in multicomponent liquid mixtures by reversed-flow gas chromatography." Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 85, no. 6 (1989): 1357. http://dx.doi.org/10.1039/f19898501357.

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23

Gorsky, V. V., and A. A. Olenicheva. "Validity of the binary diffusion law in calculating heat and mass transfer in gas mixtures with complex chemical composition." High Temperature 49, no. 1 (February 2011): 68–71. http://dx.doi.org/10.1134/s0018151x1101007x.

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Jamili, A., G. P. P. Willhite, and D. W. W. Green. "Modeling Gas-Phase Mass Transfer Between Fracture and Matrix in Naturally Fractured Reservoirs." SPE Journal 16, no. 04 (July 15, 2011): 795–811. http://dx.doi.org/10.2118/132622-pa.

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Summary Gas injection in naturally fractured reservoirs maintains the reservoir pressure and increases oil recovery primarily by gravity drainage and to a lesser extent by mass transfer between the flowing gas in the fracture and the porous matrix. Although gravity drainage has been studied extensively, there has been limited research on mass-transfer mechanisms between the gas flowing in the fracture and fluids in the porous matrix. This paper presents a mathematical model that describes the mass transfer between a gas flowing in a fracture and a matrix block. The model accounts for diffusion and convection mechanisms in both gas and liquid phases in the porous matrix. The injected gas diffuses into the porous matrix through gas and liquid phases, causing the vaporization of oil in the porous matrix, which is transported by convection and diffusion to the gas flowing in the fracture. Compositions of equilibrium phases are computed using the Peng-Robinson EOS. The mathematical model was validated by comparing calculations to two sets of experimental data reported in the literature (Morel et. al. 1990; Le Romancer et. al. 1994), one involving nitrogen (N2) flow in the fracture and the second with carbon dioxide (CO2) flow. The matrix was a chalk. The resident fluid in the porous matrix was a mixture of methane and pentane. In the N2-diffusion experiment, liquid and vapor phases were initially present, while in the CO2 experiment, the matrix was saturated with liquid-hydrocarbon and water phases. Calculated results were compared with the experimental data, including recovery of each component, saturation profiles, and pressure gradient between matrix and fracture. Agreement was generally good. The simulation revealed the presence of countercurrent flow inside the block. Diffusion was the main mass-transfer mechanism between matrix and fracture during N2 injection. In the CO2 experiment, diffusion and convection were both important.

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Kalimov, A. B., O. V. Fedorenko, and V. N. Kossov. "NUMERICAL RESEARCH OF THE CHANGE OF REGIME FOR UNSTABLE MASS TRANSFER IN A TERNARY GAS MIXTURE HYDROGEN- NITRIC OXIDE-NITROGEN." BULLETIN Series of Physics & Mathematical Sciences 72, no. 4 (December 29, 2020): 112–16. http://dx.doi.org/10.51889/2020-4.1728-7901.17.

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On the basis of the software package "MathCad", by solving the Stefan-Maxwell diffusion equations, the evolution of the features of mass transfer in a three-component gas mixture, depending on pressure changes, has been numerically studied. In this analysis, the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter transfer through the walls of diffusion channel. Through the Rayleigh partial numbers, the influence of the pressure change on the behaviour of diffusion and convective flows is examined. The numerical results reveal that an increase in the pressure leads to a change of modes in ternary gas mixture. The present results are in good agreement with the existing experimental data.

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Liu, Binlong, Michael Finkel, and Peter Grathwohl. "Mass Transfer Principles in Column Percolation Tests: Initial Conditions and Tailing in Heterogeneous Materials." Materials 14, no. 16 (August 20, 2021): 4708. http://dx.doi.org/10.3390/ma14164708.

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Initial conditions (pre-equilibrium or after the first flooding of the column), mass transfer mechanisms and sample composition (heterogeneity) have a strong impact on leaching of less and strongly sorbing compounds in column percolation tests. Mechanistic models as used in this study provide the necessary insight to understand the complexity of column leaching tests especially when heterogeneous samples are concerned. By means of numerical experiments, we illustrate the initial concentration distribution inside the column after the first flooding and how this impacts leaching concentrations. Steep concentration gradients close to the outlet of the column have to be expected for small distribution coefficients (Kd<1 L kg−1) and longitudinal dispersion leads to smaller initial concentrations than expected under equilibrium conditions. In order to elucidate the impact of different mass transfer mechanisms, film diffusion across an external aqueous boundary layer (first order kinetics, FD) and intraparticle pore diffusion (IPD) are considered. The results show that IPD results in slow desorption kinetics due to retarded transport within the tortuous intragranular pores. Non-linear sorption has not much of an effect if compared to Kd values calculated for the appropriate concentration range (e.g., the initial equilibrium concentration). Sample heterogeneity in terms of grain size and different fractions of sorptive particles in the sample have a strong impact on leaching curves. A small fraction (<1%) of strongly sorbing particles (high Kd) carrying the contaminant may lead to very slow desorption rates (because of less surface area)—especially if mass release is limited by IPD—and thus non-equilibrium. In contrast, mixtures of less sorbing fine material (“labile” contamination with low Kd), with a small fraction of coarse particles carrying the contaminant leads to leaching close to or at equilibrium showing a step-wise concentration decline in the column effluent.

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Zhang, Kaiyi, Fengshuang Du, and Bahareh Nojabaei. "Effect of Pore Size Heterogeneity on Hydrocarbon Fluid Distribution, Transport, and Primary and Secondary Recovery in Nano-Porous Media." Energies 13, no. 7 (April 3, 2020): 1680. http://dx.doi.org/10.3390/en13071680.

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In this paper, we investigate the effect of pore size heterogeneity on fluid composition distribution of multicomponent-multiphase hydrocarbons and its subsequent influence on mass transfer in shale nanopores. The change of multi-contact minimum miscibility pressure (MMP) in heterogeneous nanopores was investigated. We used a compositional simulation model with a modified flash calculation, which considers the effect of large gas–oil capillary pressure on phase behavior. Different average pore sizes for different segments of the computational domain were considered and the effect of the resulting heterogeneity on phase change, composition distributions, and production was investigated. A two-dimensional formulation was considered here for the application of matrix–fracture cross-mass transfer and the rock matrix can also consist of different segments with different average pore sizes. Both convection and molecular diffusion terms were included in the mass balance equations, and different reservoir fluids such as ternary mixture syntactic oil, Bakken oil, and Marcellus shale condensate were considered. The simulation results indicate that oil and gas phase compositions vary in different pore sizes, resulting in a concentration gradient between the two adjacent pores of different sizes. Given that shale permeability is extremely small, we expect the mass transfer between the two sections of the reservoir/core with two distinct average pore sizes to be diffusion-dominated. This observation implies that there can be a selective matrix–fracture component mass transfer as a result of confinement-dependent phase behavior. Therefore, the molecular diffusion term should be always included in the mass transfer equations, for both primary and gas injection enhanced oil recovery (EOR) simulation of heterogeneous shale reservoirs.

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Loos, Jan-Baptist W. P., Peter J. T. Verheijen, and Jacob A. Moulijn. "Numerical Simulation of the Generalized Maxwell-Stefan Model for Multicomponent Diffusion in Microporous Sorbents." Collection of Czechoslovak Chemical Communications 57, no. 4 (1992): 687–97. http://dx.doi.org/10.1135/cccc19920687.

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The results of simulations of transient multicomponent surface diffusion in a microporous adsorbent are given for various conditions. The generalized Maxwell-Stefan theory was applied to describe the diffusion phenomena. The diffusion equations were solved numerically. The transient uptake of a binary mixture and the counterdiffusion of two sorbate species in a slab were simulated. Some striking phenomena of multicomponent diffusion are presented. The relation to the approximate solution obtained by the linearized theory of multicomponent mass transfer is discussed. The simulations are compared with various results found in the literature.

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Urazov, R. R. "Simulation of the operation of the gas refrigerator recurrent complicated ethylene polymer deposits." Proceedings of the Mavlyutov Institute of Mechanics 11, no. 2 (2016): 199–204. http://dx.doi.org/10.21662/uim2016.2.029.

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The work based on the methods and equations of mechanics of multiphase media, the resulting system of ordinary differential equations, describing hydrodynamic and heat and mass transfer processes in counterflow heat exchangers type “pipe in pipe”, where the inner tube flows a mixture of ethylene and polyethylene, and in the annular space counter-current moves water. For gas mixtures is complicated by the “sticking” of liquid polyethylene on the walls of the pipe. In describing the process of formation of the polymer film is considered one of the possible mechanisms for the admission of liquid polyethylene particles from the turbulent core to the surface of the pipe, the turbulent diffusion. The results of studies on the dynamics of accumulation of the plastic film on the inner surface of gas refrigerator returnable ethylene. It is established that the formation of the profile of sediments is complex: the maximum film thickness is shifted to the output section of the channel.

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Alharbi, Wafa Nazzal, Waseem Sharaf Saeed, Abdulrahman A. Alwarthan, Ahmed Yacine Badjah-Hadj-Ahmed, and Taieb Aouak. "Extraction of Organic Volatile Pollutants in Over-Saturated Water by Pervaporation Technique Using a Poly (Dimethylsiloxane)-Based Sealer as a Membrane." Water 13, no. 8 (April 11, 2021): 1049. http://dx.doi.org/10.3390/w13081049.

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SILICONE1200 is an inexpensive domestic poly (dimethylsiloxane)-based sealer that was used in this study to remove volatile organic compounds from over-saturated water using the pervaporation technique. A series of volatile organic liquid compounds representing an important part of polluting organic products released every day in water were chosen for this study. These products were alkyl halides (chloroform), aromatics (toluene), aliphatic hydrocarbons (heptanes), ketones and aldehydes (butanone), and organosulfides (thiophene). The mass transfer of these compounds and their mixtures through the SILICONE1200 membrane was assessed to predict the results of the separation process. The results indicate that the mechanism of diffusion obeyed a Fickian model. Different parameters affecting the pervaporation results, such as the membrane thickness, stirring rate, and temperature, were examined to determine the optimal conditions in terms of the total flux and selectivity. The optimized parameters were then applied to the separation of an organic mixture from polluted water using the dynamic pervaporation process with promising results.

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Kangroa, Ilmars, and Harijs Kalis. "ON MATHEMATICAL MODELLING OF THE SOLID-LIQUID MIXTURES TRANSPORT IN POROUS AXIAL-SYMMETRICAL CONTAINER WITH HENRY AND LANGMUIR SORPTION KINETICS." Mathematical Modelling and Analysis 23, no. 4 (October 9, 2018): 554–67. http://dx.doi.org/10.3846/mma.2018.033.

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In this paper we study diffusion and convection filtration problem of one substance through the pores of a porous material which may absorb and immobilize some of the diffusing substances. As an example we consider round cylinder with filtration process in the axial direction. The cylinder is filled with sorbent i.e. absorbent material that passed through dirty water or liquid solutions. We can derive the system of two partial differential equations (PDEs), one expressing the rate of change of concentration of water in the pores of the sorbent and the other - the rate of change of concentration in the sorbent or kinetical equation for absorption. The approximation of corresponding initial boundary value problem of the system of PDEs is based on the conservative averaging method (CAM). This procedure allows reducing the 2-D axisymmetrical mass transfer problem decribed by a system of PDEs to initial value problem for a system of ordinary differential equations (ODEs) of the first order. We consider also model 1-D problem for investigation the depending the concentration of water and sorbent on the time.

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32

Kossov, Vladimir, Olga Fedorenko, Adilet Kalimov, and Aiym Zhussanbayeva. "Diffusion Mechanisms for the Occurrence of the Instability of Mechanical Equilibrium of a Ternary Gas Mixture Containing Carbon Dioxide." Fluids 6, no. 5 (May 1, 2021): 177. http://dx.doi.org/10.3390/fluids6050177.

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Mixing of carbon dioxide dissolved in a multicomponent gas mixture at different pressures was researched. It was found that the mechanical equilibrium of the ternary gas mixture 0.4163H2 (1) + 0.5837CO2 (2) − N2 (3) is violated at a pressure of p = 0.7 MPa and structured flows appear in the system. The pressure area (from 0.7 to 1.5 MPa) at which the conditions of priority transfer of components with the highest molecular weight in the mixture are realised in the system is fixed. To analyse the effect of pressure on the process of changing “diffusion–convection” modes, a mathematical model, which takes into account the kinetic features of multicomponent mixing, was applied. It was shown that the change in the modes of mass transfer is associated with a significant difference in the diffusion ability of the components. It is noted that the difference in the diffusion coefficients of components results in the nonlinearity of the concentration distribution, which leads to the inversion of the density gradient of the gas mixture, which is the cause of convective flows.

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Hansen, A. C., and W. E. Foslien. "A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in snow." Cryosphere Discussions 9, no. 2 (March 5, 2015): 1503–54. http://dx.doi.org/10.5194/tcd-9-1503-2015.

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Abstract. The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

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Tovbin, Yu K., and A. B. Rabinovich. "Self-diffusion, mass transfer, and viscosity coefficients for a binary mixture in narrow slit-like pores." Russian Chemical Bulletin 54, no. 8 (August 2005): 1777–86. http://dx.doi.org/10.1007/s11172-006-0036-2.

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35

Kossov, Vladimir, Yuriy Zhavrin, and Olga Fedorenko. "Diffusion and Convective Instability in Ternary Gas Mixture." Applied Mechanics and Materials 378 (August 2013): 253–58. http://dx.doi.org/10.4028/www.scientific.net/amm.378.253.

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The main objective of this article is to investigate the evolution of the mass transfer regimes in three-component gas mixture subject to the pressure and the diameter of diffusion channel. Two series of experiments on gaseous diffusion instabilities are reported. In one series the stability limits are investigated as a function of pressure and diameter for the system 0.4722 He + 0.5278 Ar - N2. In the other series the convection structures are made visible with the help of shadow method. The experimentalresults reveal that an increase in the pressure and the diameter of diffusion channel leads to a change of the type of mixing in ternary gas mixture.Numerical analysis of the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter through the walls of diffusion channel. Through the Rayleigh partial numbers, the influences of the pressure and the diameter of diffusion channel on the behaviour of diffusion and convective flows are examined. The present results are in good agreement with the experimental data.

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36

Hansen, A. C., and W. E. Foslien. "A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow." Cryosphere 9, no. 5 (September 23, 2015): 1857–78. http://dx.doi.org/10.5194/tc-9-1857-2015.

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Abstract. The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the effective thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for effective thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

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37

Veres, P., J. B. Gilman, J. M. Roberts, W. C. Kuster, C. Warneke, I. R. Burling, and J. de Gouw. "Development and validation of a portable gas phase standard generation and calibration system for volatile organic compounds." Atmospheric Measurement Techniques 3, no. 3 (June 16, 2010): 683–91. http://dx.doi.org/10.5194/amt-3-683-2010.

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Abstract. We report on the development of an accurate, portable, dynamic calibration system for volatile organic compounds (VOCs). The Mobile Organic Carbon Calibration System (MOCCS) combines the production of gas-phase VOC standards using permeation or diffusion sources with quantitative total organic carbon (TOC) conversion on a palladium surface to CO2 in the presence of oxygen, and the subsequent CO2 measurement. MOCCS was validated using three different comparisons: (1) TOC of high accuracy methane standards compared well to expected concentrations (3% relative error), (2) a gas-phase benzene standard was generated using a permeation source and measured by TOC and gas chromatography mass spectrometry (GC-MS) with excellent agreement (<4% relative difference), and (3) total carbon measurement of 4 known gas phase mixtures were performed and compared to a calculated carbon content to agreement within the stated uncertainties of the standards. Measurements from laboratory biomass burning experiments of formic acid by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) and formaldehyde by proton transfer reaction-mass spectrometry (PTR-MS), both calibrated using MOCCS, were compared to open path Fourier transform infrared spectroscopy (OP-FTIR) to validate the MOCCS calibration and were found to compare well (R2 of 0.91 and 0.99, respectively).

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Veres, P., J. B. Gilman, J. M. Roberts, W. C. Kuster, C. Warneke, I. R. Burling, and J. de Gouw. "Development and validation of a portable gas phase standard generation and calibration system for volatile organic compounds." Atmospheric Measurement Techniques Discussions 3, no. 1 (January 29, 2010): 333–57. http://dx.doi.org/10.5194/amtd-3-333-2010.

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Abstract. We report on the development of an accurate, portable, dynamic calibration system for volatile organic compounds (VOCs). The Mobile Organic Carbon Calibration System (MOCCS) combines the production of gas-phase VOC standards using permeation or diffusion sources with quantitative total organic carbon (TOC) conversion on a palladium surface to CO2 in the presence of oxygen, and the subsequent CO2 measurement. MOCCS was validated using three different comparisons: (1) TOC of high accuracy methane standards compared well to expected concentrations (3% relative error), (2) a gas-phase benzene standard was generated using a permeation source and measured by TOC and gas chromatography mass spectrometry (GC-MS) with excellent agreement (<4% relative difference), and (3) total carbon measurement of 4 known gas phase mixtures were performed and compared to a calculated carbon content to agreement within the stated uncertainties of the standards. Measurements from laboratory biomass burning experiments of formic acid by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) and formaldehyde by proton transfer reaction-mass spectrometry (PTR-MS), both calibrated using MOCCS, were compared to open path Fourier transform infrared spectroscopy (OP-FTIR) to validate the MOCCS calibration and were found to compare well (R2 of 0.91 and 0.99 respectively).

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39

Zhang, Rui Hua. "Numerical Simulation and Influencing Factors Analysis of the Leakage and infiltration diffusion for Fuel Underground Storage Tank." Advanced Materials Research 524-527 (May 2012): 1826–34. http://dx.doi.org/10.4028/www.scientific.net/amr.524-527.1826.

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Mass and heat transfer processes of three fuels commonly used (Liquefied Petroleum Gas (LPG), gasoline, diesel oil) flow dispersing in underground environment for the leak at different zones of underground storage tank (UST) were studied. On the basis of the mass and heat transfer process analysis and employing the three-dimensional multiphase mixture flow model, the migration processes of LPG, gasoline, diesel oil in tank pond for UST leak were simulated. The velocity, density, concentration, pressure, temperature fields can be obtained. From the simulation results, the detailed analysis were performed to investigate the characteristics of the three fuels infiltration flow processes and the effects of various influencing factors on infiltration flow such as storage pressure, fuel composition, leak position of tank, position of outlet, gravity, viscous force, etc.

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40

Zhenzhen, Zhang, Guo Kai, Luo Huijuan, Song Junnan, and Qian Zhi. "Characteristics of mass transfer between gas-liquid phases in a higee reactor." Chemical Industry and Chemical Engineering Quarterly 20, no. 4 (2014): 523–30. http://dx.doi.org/10.2298/ciceq130729034z.

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In the absorption process of gas-liquid phases in Rotating Packed Bed (RPB), the liquid flow on packing was assumed to be film-flow. Based on Higbie?s penetration theory, the diffusion-reaction model in RPB was introduced to calculate the rate of gas absorption. Taking CO2 (10%)+N2(90%) gas mixture and N-methyldiethanolamine (MDEA) aqueous solution as objects, the experiments of gas absorption were carried out at different gas flow rates, rotating speeds, temperatures, liquid flow rates and MDEA mass concentrations. The experimental data were compared with calculation results to found a good agreement in the rotating speed range of 400-1100r/min. In this range, the rate of decarburization was in direct proportion to rotating speed, temperature and liquid flow rate, and inversely proportion to gas flow rate and MEDA mass concentration. The maximum deviation between experimental data and calculation results was 10%. Beyond the rotating speed of 1100 r/min, the rate of decarburization was dependent on the dynamic balance of gas-liquid system. In this area, the rate of decarburization was inversely proportion to rotating speed.

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41

Kalinchak, V. V., A. S. Chernenko, A. F. Fedorenko, A. N. Sofronkov, and V. V. Kramarenko. "Catalyst Particle Porosity Effect upon Flameless Combustion Characteristics." Фізика і хімія твердого тіла 21, no. 1 (March 29, 2020): 124–31. http://dx.doi.org/10.15330/pcss.21.1.124-131.

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The problem of heat and mass transfer of a porous catalyst particle is considered. On the her surface, including the inner surface of the pores, an irreversibly heterogeneous first-order reaction proceeds. It has been analytically shown that in a heated gas mixture, the catalyst's porosity reduces the minimum impurity's concentration of catalytic spontaneous combustion in the mixture and increases the catalyst particle's corresponding diameter. This concentration corresponds to the external kinetic and internal diffusion reaction's modes.

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42

Lin, Hai Fei, Rui Feng Ma, Shu Gang Li, Lian Hua Cheng, Hong Yu Pan, and Li Li. "Coupling Model of Evolution of Mining Fissure Elliptic Paraboloid Zone and Methane Delivery." Advanced Materials Research 734-737 (August 2013): 546–50. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.546.

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After mining, a dynamic distribution of mining fissure elliptic paraboloid zone in the overlying stratum would be formed. Based on the rock mechanics, seepage flow mechanics, mass transfer theory and elastic-plastic theory, the coal-rock mass deformation equation, mixture gas seepage equation and gas diffusion equation of the mining fissure elliptic paraboloid zone are deduced. Combined with various boundaries, initial conditions, the multi-field coupling mathematical model of mining fissure elliptic paraboloid is obtained. The model provides a theoretical basis for numerical simulation of gas drainage system layout.

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43

Wendler, B., B. Goers, and G. Wozny. "Regeneration of process water containing surfactants by nanofiltration - investigation and modelling of mass transport." Water Science and Technology 46, no. 4-5 (August 1, 2002): 287–92. http://dx.doi.org/10.2166/wst.2002.0607.

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The mechanisms in nanofiltration of aqueous solutions of different anionic surfactants and of mixture solutions of surfactants and NaCl are investigated. The surfactants used are sodium dodecylether sulfate, sodium dodecyl sulfate and sodium alkyl benzene sulfonate. High retentions in the range of 95% up to 99.9% referring to the feed concentration are found to depend on the solvent flux. If additional salt is present in the solution, the permeate quality is deteriorating because of lower solvent flux and of mass transfer due to the electrical potential. The experimental results show that convective mass transfer of surfactant through the nanofiltration membrane occurs. Consequently, an extended solution-diffusion model is used for modelling of the process. Depending on the feed composition, concentration polarisation has to be considered in the model. The calculated surfactant flux through the membrane is in good agreement with the experimental results.

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44

Shevchuk, E. P., V. A. Plotnikov, and G. S. Bektasova. "Boron Diffusion in Steel 20." Izvestiya of Altai State University, no. 1(111) (March 6, 2020): 58–62. http://dx.doi.org/10.14258/izvasu(2020)1-08.

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As is known, boriding is carried out to increase the wear resistance and corrosion resistance of iron-carbon alloys. Along with high hardness, borides, unfortunately, have very high fragility and high refractoriness. An effective way to counter the fragility of boride layers is to form a composite structure consisting of inclusions of solid borides in a more plastic matrix. Such coatings can be obtained by volumetric heating in a muffle furnace using a boron paste that besides a mixture of iron and boron powders contained ammonium hydroxide and activated carbon with or without liquid glass. Boriding of a surface is carried out at high temperatures =1000 °С for 5 minutes. It is experimentally found that the microhardness of the surface layer increased by about 30% compared with the microhardness of the substrate, and that the thickness of the boride layer depends on the presence of liquid glass in the coating. It has been established that specially calculated proportions of ammonia, liquid glass, and charcoal contribute to the formation of an extensive diffusion zone of iron borides, the formation of which is due to the anomalously high diffusion mass transfer of boron into the matrix.

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45

Burgos-Madrigal, Paulina, Diego F. Mendoza, and Mariano López de Haro. "On Entropy Generation and the Effect of Heat and Mass Transfer Coupling in a Distillation Process." Journal of Non-Equilibrium Thermodynamics 43, no. 1 (January 26, 2018): 57–74. http://dx.doi.org/10.1515/jnet-2017-0039.

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AbstractThe entropy production rates as obtained from the exergy analysis, entropy balance and the nonequilibrium thermodynamics approach are compared for two distillation columns. The first case is a depropanizer column involving a mixture of ethane, propane, n-butane and n-pentane. The other is a weighed sample of Mexican crude oil distilled with a pilot scale fractionating column. The composition, temperature and flow profiles, for a given duty and operating conditions in each column, are obtained with the Aspen Plus V8.4 software by using the RateFrac model with a rate-based nonequilibrium column. For the depropanizer column the highest entropy production rate is found in the central trays where most of the mass transfer occurs, while in the second column the highest values correspond to the first three stages (where the vapor mixture is in contact with the cold liquid reflux), and to the last three stages (where the highest temperatures take place). The importance of the explicit inclusion of thermal diffusion in these processes is evaluated. In the depropanizer column, the effect of the coupling between heat and mass transfer is found to be negligible, while for the fractionating column it becomes appreciable.

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Oubella, M’hand, M’barek Feddaoui, and Rachid Mir. "Numerical study of heat and mass transfer during evaporation of a thin liquid film." Thermal Science 19, no. 5 (2015): 1805–19. http://dx.doi.org/10.2298/tsci130128145o.

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A numerical study of mixed convection heat and mass transfer with film evaporation in a vertical channel is developed. The emphasis is focused on the effects of vaporization of three different liquid films having widely different properties, along the isothermal and wetted walls on the heat and mass transfer rates in the channel. The induced laminar downward flow is a mixture of blowing dry air and vapour of water, methanol or acetone, assumed as ideal gases. A two-dimensional steady state and elliptical flow model, connected with variable thermo-physical properties, is used and the phase change problem is based on thin liquid film assumptions. The governing equations of the model are solved by a finite volume method and the velocity-pressure fields are linked by SIMPLE algorithm. The numerical results, including the velocity, temperature and concentration profiles, as well as axial variations of Nusselt numbers, Sherwood number and dimensionless film evaporation rate are presented for two values of inlet temperature and Reynolds number. It was found that lower the inlet temperature and Re, the higher the induced flows cooling with respect of most volatile film. The better mass transfer rates related with film evaporation are found for a system with low mass diffusion coefficient.

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Akulinin, E. I., O. O. Golubyatnikov, D. S. Dvoretskii, and S. I. Dvoretskii. "Problems of analysis, optimization and control in the separation of gas mixtures." Proceedings of the Voronezh State University of Engineering Technologies 80, no. 2 (October 2, 2018): 93–100. http://dx.doi.org/10.20914/2310-1202-2018-2-93-100.

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Mathematical models of dynamics of pressure swing adsorption processes for the separation of synthesis gas (into hydrogen, carbon dioxide and carbon monoxide) and air (into oxygen, nitrogen and argon) have been developed. The models allow calculating the profiles of component concentrations and temperature of gas and solid phases, pressure and velocity of gas mixture along the height of adsorbent in relation to time. The models include the following equations: 1) processes of mass and heat transfer during the adsorption (desorption) of a sorptive (H2, CO2, COandO2, N2, Ar) by granulated zeolite adsorbents 5Aand13Х; 2) kinetics of compound diffusion transport of adsorbate and Langmuir-Freundlich isotherm (for the synthesis gas separation), kinetics of external diffusion and Dubinin-Radushkevich isotherm (for the air separation); 3) the Ergun equation for the calculation of pressure and velocity of gas mixture in adsorbent.The system of partial differential equations was solved by method of lines. The system of ordinary differential equations was solved by the fourth-order Runge-Kutta method with automatic step selection.To analyze the accuracy of mathematical models of the adsorption separation of synthesis-gas for recovery hydrogen, the relative error of the mismatch between the calculated values for the model and the experimental values of the concentration of the product (hydrogen, oxygen) in the 'steady state' (after 15-30 operating cycles of the PSA) was calculated. The maximum value of the relative error did not exceed 11.5%.Numerical studies were carried out in a wide range of changes in the time of the cycle "adsorption-desorption" and the pressure at the stage of adsorption to determine the effect of changes in temperature, composition and pressure of the initial gas mixture on the purity, recovery and temperature of production hydrogen and oxygen, as well as the relationship of the PSA unit capacity with the purity of the resulting product (hydrogen, oxygen). The problem of adaptive optimization of the process of adsorption separation of a gas mixture and obtaining hydrogen and oxygen with a maximum concentration was formulated and solved.The algorithmic and software of the automated adaptive control system was developed.

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48

Rostovtseva, Valeriia, Alexandra Pulyalina, Daria Rudakova, Ludmila Vinogradova, and Galina Polotskaya. "Strongly Selective Polymer Membranes Modified with Heteroarm Stars for the Ethylene Glycol Dehydration by Pervaporation." Membranes 10, no. 5 (April 29, 2020): 86. http://dx.doi.org/10.3390/membranes10050086.

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Hybrid membranes based on poly (2,6-dimethyl-1,4-phenylene oxide) modified with heteroarm stars (HAS) were developed to separate ethylene glycol/water mixtures by pervaporation. The HAS consist of a small branching center fullerene C 60 and twelve arms of different nature, six arms of nonpolar polystyrene and six arms of polar poly-tert-butyl methacrylate. The changes of structure and physical properties with HAS inclusion were systematically studied using SEM, X-ray diffraction analysis, TGA, and contact angle measurements. Mass transfer of ethylene glycol and water through membranes was studied by sorption and pervaporation tests. It was found that the growth of HAS content up to 5 wt% in the membrane leads to an increase in the total flux and a strong increase in the separation factor. To evaluate intrinsic properties of the penetrant–membrane system, permeability and selectivity were calculated. Overall, utilizing star-shaped macromolecules as a filler can be a promising way to improve the separation performance of diffusion membranes.

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Peaoock, Brian. "Laws & Rules: Gas Happens." Ergonomics in Design: The Quarterly of Human Factors Applications 9, no. 4 (October 2001): 4–31. http://dx.doi.org/10.1177/106480460100900402.

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Boyle's law: The volume of a given mass of gas, at constant temperature, is inversely proportional to its pressure. Dalton's law: The pressure of a mixture of gases is equal to the sum of the partial pressures of its constituents. Charles's law (Gay-Lussac's law): The volume of a given mass of gas, at constant pressure, increases by 1/273 of its value at 0°C, for every degree Centigrade rise in temperature. Henry's law: The amount of gas dissolved in a solution is directly proportional to the pressure of that gas over the solution. Law of gas diffusion: Gas molecules will diffuse from an area of higher concentration to an area of lower concentration until equilibrium is reached. Graham's law: The rate of diffusion of a gas is inversely proportional to the square of its density. Convection and forced convection: The transfer of heat in a gas or liquid is proportional to temperature difference and can be increased by increasing airflow. —Nelkon and Parker, 1962

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50

Khasanov, M. K., and G. R. Rafikova. "Analysis of methane production intensity during its displacement from a gas hydrate formation by carbon dioxide." Multiphase Systems 14, no. 3 (2019): 149–56. http://dx.doi.org/10.21662/mfs2019.3.021.

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The theoretical model is considered in the one-dimensional approximations and numerical solutions are obtained for the process of replacing methane with carbon dioxide from a hydrate in a formation saturated with methane and its hydrate when carbon dioxide is injected into the formation. The process is considered under thermobaric conditions corresponding to the stability region of methane gas and carbon dioxide and the region of existence of CO2 in the form of a gaseous phase. The case is considered when the rate of carbon dioxide hydrate formation is limited by diffusion of carbon dioxide through the formed hydrate layer between the gas mixture stream and methane hydrate. It is accepted that the hydration substitution process occurs without the release of water from the hydrate. To describe the mathematical model, the main equations are the mass conservation equations for methane, carbon dioxide and their hydrates, Darcy’s law for filtration, Fick’s law for diffusive mixing of the gas mixture, state equations for the gas phase, Dalton’s law, energy equation, diffusion equation for transport CO2 through the hydration layer at the pore microchannel scale. The dynamics of the mass flow rates of the outgoing carbon dioxide and methane recovered has been investigated. The influence of the diffusion coefficient, the absolute permeability and the length of the formation on the intensity of the methane produced as a result of the gas substitution process is analyzed. Three main stages of the process were identified: displacement of free methane from the reservoir; extraction of free methane obtained as a result of the beginning of hydrate substitution in the formation; complete conversion of methane hydrate to carbon dioxide hydrate and complete extraction of methane from the formation. It is determined how the two main factors relate to each other in terms of the degree of influence on the replacement rate: heat and mass transfer in the reservoir and the kinetics of the replacement process.

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Journal articles on the topic 'Diffusion. Mass transfer. Mixtures'

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