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Evaporation is a key process in a wide range of industrial applications. To gain a better insight into this process, investigation on the evaporation model is an important aspect. In the present study, it is found that the computation with the Hertz-Knudsen-Schrage model is not easy to converge in the numerical simulation of the evaporation with multicomponent gas. The reason for the divergence is that the Hertz-Knudsen-Schrage model will lead to an improper vapor mass fraction which is much larger than the saturated vapor mass fraction in the iterations. To improve the convergence performance, an improved model for evaporation with multicomponent gas is proposed. In the improved evaporation model, when the predicted vapor density is larger than the saturated vapor density, a strategy that calculates the volumetric mass transfer rate with the difference between the saturated vapor density and the current vapor density will be implemented. As a result, the vapor density is bounded by the saturated values and no improper large vapor mass fraction arises in the iterations. The improved evaporation model shows much better convergence performance. In the case of the present study, the improved evaporation model can converge with the time step of 5×10−6 s, while the original Hertz-Knudsen-Schrage model cannot converge with the time step of 5×10−9 s. The improved evaporation model is also compared with the empirical correlations and shows a good agreement. [ABSTRACT FROM AUTHOR]

Model equations approximating the system of Boltzmann equations for a multicomponent gas are investigated. Methods for determining parameters in relaxation terms corresponding to cross-collision integrals are analyzed. Numerical solutions based on three model systems and the Boltzmann equations are compared as applied to the following problems: relaxation of a mixture to equilibrium, shock wave structure, and the dynamics of a vapor-gas cloud generated by pulsed laser irradiation of a target. It is shown that the parameters in the relaxation operators influence the degree of difference in the solutions produced by the various models. [ABSTRACT FROM AUTHOR]

This paper contains the physical-mathematical and computational models of the flow in the air intake. The air flow is modeled as a mixture of perfect gases taking into account the dependence of thermodynamic properties on the temperature and pressure. The paper provides the results of comparing the calculated data obtained for flight conditions and bench tests. [ABSTRACT FROM AUTHOR]

Numerical simulation of supersonic combustion with transverse hydrogen injection is performed by solving the three-dimensional Favre-averaged Navier-Stokes equations coupled by the k -ω turbulence model. These equations are solved using an algorithm that is based on the third-order essentially nonoscillatory scheme. Several cases of the jet compositions (pure hydrogen and hydrogen diluted by nitrogen in 50:50 mol%) are considered to study the influence of the composition onto the structure and reactivity of the supersonic combustion systems. Seven step modified version of Spark model developed by Jachimowski is implemented to model chemical reaction of hydrogen combustion, which performs quite well in the considered relatively high temperatures. The simulation revealed that the jet penetration heights are equal for both cases, and the hydrodynamic fields looked similar except for the temperatures of the zones located ahead and behind the jet injection. The chemical reaction zone, indicated by OH radicals, was more intense for the pure hydrogen case, occupying a narrow region along the oblique shock wave line. In contrast, the use of a hydrogen/nitrogen jet mixture resulted in a significantly wider flame front zone. This suggests that the presence of nitrogen in the mixture diluted the hydrogen concentration, leading to slower combustion. The study shows that the flow properties and reactivity of the mixture significantly changing with the dilutions of the fuel composition. [ABSTRACT FROM AUTHOR]

In this paper, supersonic plane turbulent mixing layer of gases with injection of solid particles is studied numerically. The gas phase are determined by DNS solving the multi-species Navier-Stokes equations in the Eulerian approach, and the dynamic of solid particles are traced in the Lagrangian approach. The dynamics of hydrogen -- air mixing and the formation of the vortex system in the mixing layer and its effect on the distribution of solid particles in the two free-flow speeds are investigated. The study focuses on detailed analysis an influence of the vortex system in the supersonic turbulent mixing layer on the dispersion solid particles with different size. The results show that heavy particles almost do not react to vortex structures. It is revealed that medium particles tend to accumulate along the circumference of the vortex and along the braid between the two vortices. A quasi-equilibrium state with a gas flow of light particles is established. [ABSTRACT FROM AUTHOR]

A general finite element model and a new solution method were developed to simulate the permeances of Lintz Donawiz converter gas (LDG) components and the performance of a polysulfone membrane separation unit. The permeances at eight bars of CO, N2, and H2 in LDG simulated using the developed model equations employing the experimental mixed gas data were obtained by controlling the finite element numbers and comparing them with pure gas permeation data. At the optimal finite element numbers (s = 15, n = 1), the gas permeances under the mixed-gas condition were 6.3% (CO), 3.9% (N2), and 7.2% (H2) larger than those of the pure gases, On the other hand, the mixed-gas permeance of CO2 was 4.5% smaller than that of pure gas. These differences were attributed to the plasticization phenomenon of the polysulfone membrane used by CO2. The newly adopted solution method for the stiff nonlinear model functions enabled the simulation of the performance (in terms of gas recovery, concentration, and flow rate) of the first-stage membrane within two seconds under most gas flow conditions. The performance of a first-stage membrane unit separating LDG could be predicted by the developed model with a small error of

The work is devoted to the numerical simulation of a supersonic plane mixing layer of multicomponent gases in the presence of injection of particles at the interface of flows. A. algorithm for solving the system of Navier-Stokes equations for the gas phase and the system of ordinary differential equations for solid particles based on the Eulerian-Lagrangian representation is proposed I. is assumed that the turbulent flow is quasi-two-dimensional and the solution of the an original system is produced by the 2D-DNS approach without using additional closure models of turbulence. A detailed study of the influence of the gas phase on the particles distribution and their capture with coherent structures is performed with the variance of Mach numbers and particles injection locations The enhancing influence of the centrifugal force on the dispersion of particles is obtained with increase in the input Mach number. A quasi-equilibrium state with a gas flow of small particles is established. [ABSTRACT FROM AUTHOR]

An original method for calculating the equilibrium pressure for the formation or dissociation of multicomponent gas hydrates as a function of temperature and composition has been developed. It is applicable to gas and water systems that are in the following phase states: gas–water vapor–ice; gas–water vapor–liquid water. The developed method is suitable for determining the equilibrium conditions for the formation (dissociation) of hydrates of multicomponent gases depending on their composition with an accuracy of about 1%. The novelty of the developed method is protected by a patent of the Russian Federation. [ABSTRACT FROM AUTHOR]

Abstract Within microchannels, rarefied gas molecules frequently interact with the channel wall, resulting in non-zero velocity at the wall. This phenomenon is known as the gas slippage effect or Klinkenberg effect in porous media. Although the gas slippage effect of single component gas has been thoroughly investigated, an accurate correlation to account for the gas slippage effect in multicomponent gas flow has not been formulated so far. In this paper, we aim to quantify the multicomponent gas slippage effect by deriving a non-empirical second-order correlation. Our approach is based on kinetic theory. We calculate the mean free path of gas mixtures, and capture the loss of horizontal flux momentum of gas flux after the molecules diffusively reflect at the wall. The horizontal flux momentum acts as shear stress on gas flow. In this sense, the loss of momentum induces reduction of viscosity and enhancement of mass transfer. By quantifying the loss of horizontal momentum as well as the reduction of viscosity, we can solve the gas slippage coefficient for the multicomponent gas flow system. Our model captures the mass transfer mechanism of gas mixtures at low pressure (near-ideal condition). The accuracy of our model has been validated by both molecular-level simulation data and physical experimental data. The difference between our results and benchmark data is within 10% for Knudsen number up to 1. Our model can be readily applied to the numerical simulation of unconventional gas formations. [ABSTRACT FROM AUTHOR]

A prediction model of shale gas content was established based on the volumetric method. The total gas content of shale includes gas in the adsorbed phase and free phase. The amount of gas in the adsorbed phase was calculated with the consideration of mineral composition of shale, temperature, pressure, moisture and non-methane gas, and in the calculation of gas amount in the free phase the adsorbed phase volume was con-sidered. The model validation was conducted with the experimental data of in-situ desorption of JY-1 well in Fuling Jiaoshiba area. The results show that when the adsorbed phase volume is considered, the gas content calculated by the model is in good agreement with the field desorption data. Hwever, when the adsorbed phase volume is not considered, the gas content is overestimated by27%-38%. Moisture has little effect on the gas content of shale. Multicomponent gas not only changes the gas content of shale, but also changes the occurrence state of shale gas. The gas content will be overestimated by 5. 6%-31. 8%without the consideration of multicomponent gas. The accuracy of the model greatly depends on the results of indoor experiments. To obtain an accurate shale gas content, a further study of adsorption experiments of multicomponent gas on moisture-equilibrated shale should be carried out in the future study. [ABSTRACT FROM AUTHOR]

In order to explore the thermodynamic mechanism of multicomponent gas adsorption on coal, the Grand Canonical Monte Carlo simulation method was used to study the adsorption behavior of CH4, CO2 and N2 in the coal molecular model at different temperatures from the perspective of thermodynamics. The simu-lation results show that CH4 shows a dotted distribution, CO2 shows a cluster distribution, and N2 shows a strip distribution in the unit cell. The relationship between the adsorption capacity, adsorption heat and adsorption entropy of the three gases is CO2> CH4> N2. And the relationship between the adsorption potential of the three gases is CO2

Thermal diffusion factor (TDF) measurements were performed for one quaternary, for four ternary, and for six binary gaseous systems, containing $$\hbox {H}_{2}, \, \hbox {CH}_{4}, \, \hbox {N}_{2}$$ , and $$\hbox {CO}_{2}$$ held under atmospheric pressure and at cold- and hot-chamber temperatures of $$T_{1}$$ = 280 K and $$T_{2}$$ = 800 K, respectively. For the multicomponent gas mixtures, measurements were made at different values of the mole fraction of the additive. Also, the dependence of the TDF values on the mole fraction of the additive for the multicomponent mixtures was analyzed. A semi-empirical formula to calculate TDF values was proposed; this formula gives results that are in good agreement with experimental data within the respective limits of error. [ABSTRACT FROM AUTHOR]

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Abstract: This study proposes a strategy for optimal design of hollow fiber membrane networks for post combustion carbon capture from power plant multicomponent flue gas. A mathematical model describing multicomponent gas permeation through a separation membrane was customized into the flowsheet modeling package ASPEN PLUS. An N-stage membrane network superstructure was defined considering all possible flowsheeting configurations. An optimization formulation was then developed and solved using an objective function that minimizes the costs associated with operating and capital expenses. For a case study of flue gas feed flow rate of 298 m3/s with 13% CO2 and under defined economic parameters, the optimization resulted in the synthesis of a membrane network structure consisting of two stages in series. This optimal design was found while also considering feed and permeate pressures as well as recycle ratios between stages. The cost of carbon capture for this optimal membrane network is estimated to be $28 per tonne of CO2 captured, considering a membrane permeance of 1000 GPU and membrane selectivity of 50. Following this approach, a reduction in capture cost to less than $20 per tonne CO2 captured is possible if membranes with permeance of 2000 GPU and selectivity higher than 70 materialize. [Copyright &y& Elsevier]

This paper analysed the performance of a membrane system over key design/operation parameters. A computation methodology is developed to solve the model of hollow fibre membrane systems for multicomponent gas feeds. The model represented by a nonlinear differential algebraic equation system is solved via a combination of backward differentiation and Gauss-Seidel methods. Natural gas sweetening problem is investigated as a case study. Model parametric analyses of variables, namely feed gas quality, pressure, area, selectivity and permeance, resulted in better understanding of operating and design optima. Particularly, high selectivities and/or permeabilities are shown not to be necessary targets for optimal operation. Rather, a medium selectivity (<60 in the given example) combined with medium permeance (~300-500 x 10-10 mol/s m² Pa in the given case study) is more advantageous. This model-based membrane systems engineering approach is proposed for the synthesis of efficient and cost-effective multi-stage membrane networks. [ABSTRACT FROM AUTHOR]

The modeling and optimal design/operation of gas membranes for postcombustion carbon capture (PCC) is presented. A systematic methodology is presented for analysis of membrane systems considering multicomponent flue gas with CO2 as target component. Simplifying assumptions is avoided by namely multicomponent flue gas represented by CO2/N2 binary mixture or considering the co/countercurrent flow pattern of hollow-fiber membrane system as mixed flow. Optimal regions of flue gas pressures and membrane area were found within which a technoeconomical process system design could be carried out. High selectivity was found to not necessarily have notable impact on PCC membrane performance, rather, a medium selectivity combined with medium or high permeance could be more advantageous. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]

The interaction of a planar supersonic air flow with the hydrogen jet injected perpendicularly across the slot from the duct walls is studied numerically. An algorithm is constructed for solving the Favre-averaged Navier - Stokes equations for the flow of a thermally perfect multicomponent gas based on the ENO scheme. The influence of the jet Mach number and the ratio of the jet and flow pressures on the shockwave structure of the flow and the jet penetration depth is shown. [ABSTRACT FROM AUTHOR]

A general finite element model and a new solution method were developed to simulate the permeances of Lintz Donawiz converter gas (LDG) components and the performance of a polysulfone membrane separation unit. The permeances at eight bars of CO, N 2 , and H 2 in LDG simulated using the developed model equations employing the experimental mixed gas data were obtained by controlling the finite element numbers and comparing them with pure gas permeation data. At the optimal finite element numbers ( s = 15, n = 1), the gas permeances under the mixed-gas condition were 6.3% (CO), 3.9% (N 2 ), and 7.2% (H 2 ) larger than those of the pure gases, On the other hand, the mixed-gas permeance of CO 2 was 4.5% smaller than that of pure gas. These differences were attributed to the plasticization phenomenon of the polysulfone membrane used by CO 2 . The newly adopted solution method for the stiff nonlinear model functions enabled the simulation of the performance (in terms of gas recovery, concentration, and flow rate) of the first-stage membrane within two seconds under most gas flow conditions. The performance of a first-stage membrane unit separating LDG could be predicted by the developed model with a small error of <2.1%. These model and solution methods could be utilized effectively for simulating gas permeances of the membrane that is plasticized severely by the permeating gas and the separation performance of two- or multi-stage membrane processes.