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This study reports the separation of pure hydrogen (H 2) employing pressure swing adsorption (PSA). The Li-X and Li-hierarchical X (Li–H-X) zeolite were prepared by an ion exchange process. The sorbents were evaluated through several experiments including, breakthrough, empty bed contact time (EBCT), single-bed, and two-bed PSA with different steps. The effect of pressure, purity, and recovery relationship was developed. The high-pressure PSA study was performed at 4, 6, and 10 bar with varying feed flow rates to assess their efficacy in pure H 2 separation using binary gas stream (H 2 /CO 2 , 75/25 vol.%). The breakthrough adsorption capacity of Li–H-X exhibited 3.4 mmol g−1 and 0.212 mmol g−1 of CO 2 and H 2 , respectively. Li–H-X shows ∼8% higher CO 2 sorption capacity than the Li-X sorbent at 1 bar and 300 K due to the large meso-microporous structure of the sorbent. The two-bed PSA purity and recovery were found higher than single-bed PSA. Using two-bed PSA, the Li–H-X achieved a 99.5% of purity, 92.9% of recovery, and 10.4 mL min−1 g−1 of productivity, which was ∼16% higher recovery and productivity than single-bed PSA at a flow rate of 1200 mL min−1 at 6 bar. With increasing the pressure and flow rate, the recovery of Li–H-X was enhanced up to 93.7% with 99.1%–99.9% H 2 purity. The long-term PSA was run using Li–H-X sorbent for 7.5 h with 230 cycles with H 2 purity between 98.5 and 99.5% at 6 bar. Interestingly, the adsorbent shows the scalability of PSA for efficient H 2 separation for a binary mixture of H 2 /CO 2. [Display omitted] • Li–H-X was evaluated using single and two-bed PSA using different conditions. • H 2 purity & recovery of Li–H-X sorbent was higher than Na-X and Li-X adsorbent. • H 2 recovery was higher in two bed PSA compare to sing bed PSA. • PSA cycles were run for a long duration with a marginal decrease in H 2 purity. • Li–H-X was potential sorbent for pure H 2 separtion from binary gas mixture. [ABSTRACT FROM AUTHOR]

Working fluid selection for closed-cycle turbo-refrigerators (CCTRs) for deep freezing, as a more fundamental topic, has not yet received careful consideration, leading to limitations in attempts to optimizing CCTR design in the early stages of cycle design. This paper proposed the working fluid selection criteria that to select the one leading to the lowest system weight and volume without compromising the system energy efficiency. Design criteria, such as specific speed and Reynolds number, and their dependence on fluid properties are introduced to ensure uncompromising-efficiency design of turbomachinery. Normalized heat transfer area of recuperator correlated with fluid properties is derived as the evaluation criterion for system weight and volume. Applying the proposed criteria, the comparison between potential pure gases shows the normalized heat transfer areas required for nitrogen, neon, and argon are 1, 1.54 and 2.18, respectively. Therefore, nitrogen among all pure gases has the greatest potential to reduce system weight and volume. The comparison among potential binary mixtures highlights the methane-nitrogen mixture with the molar mass of 24.1 g/mol which reduces the required heat transfer area by approximately 20 % compared to pure-nitrogen-based system and may reduce it by nearly up to 30 % for systems with larger cooling capacity levels.

The paper presents results of a theoretical study for parameters of a compressible boundary layer for the case of a re-entry space vehicle flying in atmosphere with the free flow at Mach 6 ≤ M ≤ 10 with sublimation of the carbon coating (graphite). Since a high flight velocity results in a higher wall temperature and a higher mass loss rate, the effect of wall material evaporation decreases the wall temperature as compared with the case of zero-sublimation flow. All that increases the gas mixture density in the sublimation vapor cloud nearby the wall; this is beneficial for stability of the high-speed boundary layer in the response to the first-mode disturbance. As for the second mode disturbances, the lower values of spatial amplification rate with increasing Mach number is observed due to the surface material sublimation. The position of laminar-turbulent transition was evaluated using the eN method. Our computations demonstrated that (for a flow with M = 6) the surface sublimation has no influence for laminar-turbulent transition; this transition is governed by the growth of three-dimensional (3D) first mode disturbances. At higher Mach numbers (for M = 8 and higher) we observe that the disturbance amplification rate in the downstream direction becomes smaller. The transition is driven by a 2D second mode. The graphite coating sublimation has destabilizing influence for the second mode; that accelerates the boundary layer transition to turbulence. [ABSTRACT FROM AUTHOR]

An apparatus for high-accuracy gas density and adsorption measurements over the range of temperature from (193 to 423) K and pressure from (0 to 15) MPa is described. This instrument is based on the two-sinker densimetry principle and incorporates a magnetic suspension balance. In addition to the two "density sinkers", two "sorption sinkers" are weighed to investigate density and adsorption of a gas sample simultaneously. The design of the sinkers increases the resolution of density and adsorption investigations and enables the correction of sorption effects on density measurements. The complete apparatus, including the sinkers, the temperature and pressure measuring systems, and the measurement procedure, is described. For the density range investigated, the uncertainty (k = 2) is between (0.0034 to 0.019) kg · m−3, corresponding to (0.060 to 0.011)%. The uncertainty (k = 2) in adsorption load is (0.16 to 0.26) μ g · cm−2. Density measurements at T = (283 and 293) K and pressures up to 10 MPa of high-purity argon and nitrogen validate the instrument for density. Adsorption measurements of high-purity carbon dioxide and propane on a gold surface validate the instrument for adsorption investigation at T = (283 and 293) K and up to the saturation pressure of the investigated gas. The apparatus was used to measure the binary mixture (0.75 CO 2 + 0.25 C 3 H 8 ). In the future, the apparatus will also be used to accurately determine dew-point densities and pressures of pure gases and gas mixtures. [ABSTRACT FROM AUTHOR]

Hydrogen purification by conventional adiabatic cylindrical column and non-adiabatic plate pressure swing adsorption (NAPSA) mediated by amorphous spent coffee grounds was investigated to study the impact of the two systems on hydrogen purity and recovery from methane reforming product. The proposed NAPSA design addresses the limitations of conventional columns, namely their low recovery and dissipated adsorption heat. By recapturing the dissipated adsorption heat, the NAPSA design facilitates the regeneration and recovery of the process. This innovative approach mitigates the challenges associated with conventional column designs, allowing for improved efficiency in the regeneration and recovery stages. Both systems yielded high hydrogen purity of 99.99%, attributed to the favorable characteristics of the adsorbent. Characterization of the spent coffee sample showed that the sample exhibited some forms of layered structure embedded with calcium and carbonate ions within the structure. Despite better mass transfer in the conventional adiabatic system, the non-adiabatic plate PSA system was capable of retaining carbon dioxide in the adsorbent bed longer due to better heat dissipation. As a result, the non-adiabatic PSA system improved the hydrogen recovery by 5.2%. Extended carbon dioxide retention time and good heat transfer management were found important in resolving the inherent trade-off issue between the purity and recovery that exists in the present gas purification system.

The special flow phenomenon in microflow, molecular exchange flow, can be used for gas separation. The mathematic models to describe principles of molecular exchange flow are established by illustrating a novel gas separator with similar structure to the Knudsen pump based on thermal transpiration effect. The ratio of temperature gradient to pressure gradient is employed to determine the characteristics of molecular exchange flow. Taking binary gas mixtures of He–Ne, He-Ar and Ne–Ar as examples, the construct conditions and influence factors on flow behaviors are investigated on negative/ideal/positive molecular exchange flows. The limiting ratios of temperature gradient to pressure gradient are sensitive to Knudsen number. The intensity of molecular exchange flow is greatly affected by not only mole fractions of gas components but also Knudsen number. The temperature difference and implicitly corresponding pressure difference should be carefully chosen since they are the driving forces for molecular exchange flow phenomena. The intensities and construct conditions of molecular exchange flows are closely related to the properties of species in gas mixtures. [ABSTRACT FROM AUTHOR]

• This paper focuses on the defect of high driving power caused by the low density of helium coolant in the tritium breeding blanket of CFETR. Based on extensive research, a novel approach is proposed to mix supercritical CO2 into the blanket to optimize the driving power and improve the energy conversion efficiency. The innovations are summarized as follows. • The change of coolant property as a function of temperature and the constant property parameters show that the change of property with temperature cannot be ignored.Therefore, the physical parameters of coolants with different mixing ratios are fitted, and a UDF program is developed to calculate them. • The necessary fan driving power for different gas mixtures is calculated based on the calculation results of the first wall under different coolants and the data of Helium coolant in the whole blanket, and the energy proportion of the fan driving power in the total thermal power of the reactor is determined. • Combined with the energy conversion system of the secondary loop, the thermal-electric conversion efficiency of the whole reactor is calculated. It is found that the mixture with the lowest fan driving power may not necessarily have the highest thermal-electric conversion efficiency, which provides some value for further research. The first wall of the tritium breeding blanket is an important high-heat flux component in fusion reactors, and its thermal analysis is critical. Helium is chosen as the coolant for the CFETR tritium breeding blanket due to its good compatibility with structural materials and excellent thermal properties. However, its low density requires a significant amount of drive power. After extensive feasibility research, using He-CO 2 mixture as coolant is one of the main optimization directions. In this paper, a new method is proposed to consider the variation of thermal properties parameters of the He-CO 2 mixture with temperature. A fitting formula for the He-CO 2 mixture at different ratios under 12MPa is provided, and the mixture is simulated in the commercial CFD software Fluent by compiling a UDF program. The results show that the optimum He mole fraction in the He-CO 2 mixture is 60%, which reduces the required drive power by 89.36% compared with using pure He as coolant and by 81.57% compared with using CO 2.With further programming calculations and considering the effect of the secondary circuit, it is calculated that the highest energy conversion efficiency is 29.43%.This study provides valuable insights into the thermal-hydraulic performance of the tritium breeding blanket with a binary gas mixture coolant in fusion reactors. [ABSTRACT FROM AUTHOR]

A numerical study of the gas dynamics of the processes of the outflow of a rarefied binary gas mixture with a large ratio of the species mass from the source into vacuum is carried out. The calculations are performed by the direct simulation Monte Carlo method. The effect of increasing the density of the heavy species in the vicinity of the outlet of the source is revealed. A significant effect of the light species on the gas dynamics of the mixture is shown, leading to an increase in flow rate and an enhancement of the effect of axial focusing of the heavy species. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical study for a supersonic boundary layer over a flat plate in a stream of air at Mach number M = 2 under the conditions of surface sublimation. The sublimation-prone material is naphthalene (C10H8). Calculations demonstrated that at a higher surface temperature the mass flowrate of naphthalene evaporation is increasing. This reduces the wall temperature in comparison with a similar flow without sublimation. The high molecular mass of naphthalene (vs. air) and reduction of wall temperature due to the wall material evaporation creates a higher density of the binary gas mixture (air and naphthalene vapor) near the wall. This modification of the boundary layer profiles induces a significant reduction of instability growth rate. This fact was confirmed by calculations based on the linear stability theory. It was found that boundary layer stabilization occurs for growing sublimation surface temperature; it becomes a maximum near the triple point temperature of the coating material. The eN method gives the estimates of the Reynolds number for laminar-turbulent transition. This shows a theoretical possibility of extension of the laminar boundary layer above a model with sublimation coating. [ABSTRACT FROM AUTHOR]

Palladium (Pd) membranes are characterized by their high permselectivity to hydrogen and easy operation, and are promising devises for separating hydrogen from hydrogen-rich gases. The membranes are normally operated with atmospheric pressure at the permeate side. Instead of this common operation, hydrogen permeation through a Pd membrane under vacuum operation at the permeate side is investigated and compared with that under normal operation. In this study, two membrane operating temperatures (320 and 380 °C), four H 2 partial pressure differences (2, 3, 4, and 5 atm) across the membrane, and four feed gases are considered. The results suggest that the vacuum operation can efficiently intensify the H 2 permeation rate. The improvement in H 2 permeation rate due to the vacuum operation can be increased up to 136%. The positive effect of the vacuum operation is especially pronounced when the gas mixtures are used as the feed gases, stemming from the effective attenuation of the concentration polarization. An increase in membrane temperature raises the H 2 permeation rate, but its influence in enhancing the H 2 permeation rate with the vacuum operation is not as significant as that without the vacuum one. It is found that the retardation effect of impurities on the mass transfer is always ranked as CO > CO 2 > N 2 , regardless of with/without vacuum operation. • Hydrogen separation by a palladium (Pd) membrane with/without vacuum is studied. • Vacuum operation can intensify the H 2 permeation rate significantly, especially in gas mixture. • Vacuum operation can effectively attenuate H 2 boundary layer and concentration polarization. • Retardation effect of impurities on H 2 permeation rate follows the order of CO > CO 2 > N 2. • Improvement in H 2 permeation rate by vacuum operation can be intensified up to 136%. [ABSTRACT FROM AUTHOR]

The effect of CO2‐philic additive polyethylene glycol (PEG) 200 in Matrimid 5218 on the separation performance of prepared membranes was evaluated in a binary gas mixture. Matrimid/PEG 200 flat‐sheet blended membranes with low PEG concentrations were prepared by the dense film‐casting method. Pure Matrimid and blended membranes were characterized by FTIR spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and permeation measurements. The addition of 4–5 % of PEG enhanced considerably the CO2 permeability of the Matrimid matrix. The best formulation, Matrimid/PEG 200 (96/4), showed in comparison to pure Matrimid a more than threefold increase in CO2 permeability and an increase in separation factor of about 40 %. Matrimid gas separation membranes are widely studied for carbon dioxide capture from gas mixtures such natural gas and biogas, despite their rather low permeabilities. Blending Matrimid with low concentrations of polyethylene glycol can roughly triple the carbon dioxide permeability and also increases the carbon dioxide/methane separation factor. [ABSTRACT FROM AUTHOR]

We deal with the so-called four-equation model for dynamics of the heterogeneous binary mixtures of the Noble-Abel stiffened-gases (NASGes). In relation to the quasi-homogeneous form of the model, we suggest a new insight on a quadratic equation for the pressure, give a simple formula for the squared speed of sound and present a new proof for a formula connecting it to the Wood speed of sound. A short derivation of the balance equation for the pressure is included as well. [ABSTRACT FROM AUTHOR]

A power-law mixing rule has been developed to determine apparent diffusion coefficient of a binary gas mixture on the basis of molecular diffusion coefficients for pure gases in heavy oil. Diffusion coefficient of a pure gas under different pressures and different temperatures is predicted on the basis of the Hayduk and Cheng's equation incorporating the principle of corresponding states for one-dimensional gas diffusion in heavy oil such as the diffusion in a pressure-volume-temperature (PVT) cell. Meanwhile, a specific surface area term is added to the generated equation for three-dimensional gas diffusion in heavy oil such as the diffusion in a pendant drop. In this study, the newly developed correlations are used to reproduce the measured diffusion coefficients for pure gases diffusing in three different heavy oils, i.e., two Lloydminster heavy oils and a Cactus Lake heavy oil. Then, such predicted pure gas diffusion coefficients are adjusted based on reduced pressure, reduced temperature, and equilibrium ratio to determine apparent diffusion coefficient for a gas mixture in heavy oil, where the equilibrium ratios for hydrocarbon gases and CO2 are determined by using the equilibrium ratio charts and Standing's equations, respectively. It has been found for various gas mixtures in two different Lloydminster heavy oils that the newly developed empirical mixing rule is able to reproduce the apparent diffusion coefficient for binary gas mixtures in heavy oil with a good accuracy. For the pure gas diffusion in heavy oil, the absolute average relative deviations (AARDs) for diffusion systems with two different Lloydminster heavy oils and a Cactus Lake heavy oil are calculated to be 2.54%, 14.79%, and 6.36%, respectively. Meanwhile, for the binary gas mixture diffusion in heavy oil, the AARDs for diffusion systems with two different Lloydminster heavy oils are found to be 3.56% and 6.86%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] A complete analysis of the phase diagram of the adsorption lattice gas model of a binary gas mixture on one-dimensional and honeycomb lattices in the ground state with nearest neighbor interactions between particles was carried out. We found that in the parameter space of the lateral interactions for one-dimensional and honeycomb lattices, their division into regions with different topologies of phase diagrams is the same as for a square lattice. [ABSTRACT FROM AUTHOR]

Results of experimental studies of the gas mixture (laser active medium) effect on the lasing energy and overall efficiency of excimer discharge ArF (193 nm), KrCl (222 nm) KrF (248 nm), and XeCl (308 nm) lasers operating in buffer-free gas mixtures are presented. The optimal (in terms of maximum radiation energy) ratios of the gas components of the excimer laser active media are found, at which efficient operation is achieved with a sufficiently high power of the laser radiation. It is confirmed experimentally that for the rare gas halide discharge pumped excimer lasers the presence of a buffer gas in the active medium is not required for efficient laser operation. For example, in two-component excimer laser gas mixtures, containing working rare and halogen-containing gases, laser pulse energy of up to 170 mJ and high pulsed power of laser radiation of up to 24 MW have been attained for the first time for pulsed gas-discharge excimer lasers operating on electronic transitions at excimer ArF*, KrCl*, KrF*, and XeCl* molecules pumped by a transverse electric volume discharge of a low-pressure buffer-free gas mixture. A overall efficiency maximum of up to 0.8% was experimentally attained for binary gas mixture of KrF and XeCl lasers. [ABSTRACT FROM AUTHOR]

This paper determines analytically the oscillating frequency and onset temperature of a simple standing wave thermoacoustic heat engine as eigenvalues of wave problem. The method to treat is based on the linear theory of thermoacoustics and the analytical solution of wave equation. The influence of geometrical parameters such as stack position, stack length, engine total length, and the influence of operational parameters such as charge pressure, on the oscillating frequency and onset temperature for four different working gases of Hydrogen, Helium, Nitrogen and Argon are investigated. Moreover, the eigenvalues are calculated for binary gas mixtures of four mentioned gases. [ABSTRACT FROM AUTHOR]

The objective of the present simulation is to analyze the performance of a twin thermoacoustic prime mover using CFD in terms of frequency and pressure amplitude. Pure fluid media such as helium, argon, nitrogen and their binary gas mixtures are studied at a constant operating pressure of 5 bar. The GAMBIT 2.3.16 pre-processor is used for creating the geometry of twin prime mover and the CFD package FLUENT 6.3 is used for simulating the device with different combinations of gas mixtures. The geometrical parameters and temperature gradients across the stack are kept constant throughout the simulation. It is found that the pressure amplitude of the thermoacoustic oscillations is higher for pure argon, whereas the frequency of the oscillations is higher for helium (495 Hz) rather than other gases and mixtures. [ABSTRACT FROM AUTHOR]

This paper presents the results of experiments done for classification and quantification of two volatile organic compounds (VOCs), namely, acetone (CH3COCH3) and 2-Propanol (CH3CHOHCH3) in their single as well as in mixture forms. A sensor array consisting of four sensor elements was fabricated in our lab using thick-film fabrication technology. The steady-state responses of the sensor array were collected for the mentioned VOCs in their single as well as in mixture form. A hierarchical system consisting of gating network and three quantification networks was designed to classify and subsequently quantify the individual and mixture of VOCs. The classification accuracy results of gating network have been ensured using back-propagation neural network (BPNN) and support vector machine (SVM). For quantification multioutput support vector regression method was used in slave networks for single as well as binary mixture data. k-fold cross validation scheme was adopted for all the experiments. The average classification accuracy of gating network for the mixture data in raw form was 89.5% using BPNN and 94.7% using nu-SVM. With principal component analysis preprocessed data, the average accuracy was 95.6% with BPNN and 100% using nu-SVM, respectively. For quantification, good 0.9828 and 0.9764 correlation coefficients for the predicted versus real concentration of acetone and 2-Propanol, respectively, in mixture form were obtained. Thus, we report a promising approach for binary mixture of gases/odors analysis using thick-film gas sensor array responses. [ABSTRACT FROM PUBLISHER]

The effect of new terms in the improved algorithm, the modified direct simulation Monte-Carlo (MDSMC) method, is investigated by simulating a rarefied binary gas mixture flow inside a rotating cylinder. Dalton law for the partial pressures contributed by each species of the binary gas mixture is incorporated into our simulation using the MDSMC method and the direct simulation Monte-Carlo (DSMC) method. Moreover, the effect of the exponent of the cosine of deflection angle (α) in the inter-molecular collision models, the variable soft sphere (VSS) and the variable hard sphere (VHS), is investigated in our simulation. The improvement of the results of simulation is pronounced using the MDSMC method when compared with the results of the DSMC method. The results of simulation using the VSS model show some improvements on the result of simulation for the mixture temperature at radial distances close to the cylinder wall where the temperature reaches the maximum value when compared with the results using the VHS model. [ABSTRACT FROM AUTHOR]

Abstract: Designs and analyses models of centrifugal-flow compressor and radial-inflow turbine of Brayton Rotating Units (BRUs) are developed for 15 and 40g/mole He–Xe working fluids. Also presented are the performance results of a space power system with segmented, gas cooled fission reactor heat source and three Closed Brayton Cycle loops, each with a separate BRU. The calculated performance parameters of the BRUs and the reactor power system are for shaft rotational speed of 30–55krpm, reactor thermal power of , and turbine inlet temperature of 900–1149K. With 40g/mole He–Xe, a power system peak thermal efficiency of 26% is achieved at rotation speed of 45krpm, compressor and turbine inlet temperatures of 400 and 1149K and 0.93MPa at exit of the compressor. The corresponding system electric power is , working fluid flow rate is 1.85kg/s and the pressure ratio and polytropic efficiency are 1.5% and 86.3% for the compressor and 1.42% and 94.1% for the turbine. For the same nominal electrical power of , decreasing the molecular weight of the working fluid (15g/mole) decreases its flow rate to 1.03kg/s and increases the system pressure to 1.2MPa. [Copyright &y& Elsevier]

Abstract: In this work, we simulate the transient behaviour of gas purification systems employing silica derived membranes and formulate a model that is capable of predicting this transient behaviour in the presence of a CO2 and H2, both as single gases and as a binary gas mixture. The model is based on continuity and assumes that the membrane properties do not change between single gas and mixed gas cases. Based on these properties, the complete characterization of transient membrane performance is obtained thereby providing an explanation based upon driving forces for very significant differences between single and mixed gas measurements. The simulated results are validated with independent mixed gas experiments and are then extended to analyse the difference in performance for a gas separation system with mixed gas feed using membranes with at least one order of magnitude difference in selectivity based on single gas permeations. The model also allows simulation for membranes complying with temperature dependency mechanism. Our results show that the increase in performance of the system for mixed gas feed is not commensurate with the increase in the selectivity based on single gas permeations. [Copyright &y& Elsevier]

Abstract: The Chapman–Enskog solutions of the Boltzmann equation provide a basis for the computation of important transport coefficients for both simple gases and gas mixtures. These coefficients include the viscosity, the thermal conductivity, and the diffusion coefficient. In a preceding paper (I), for simple, rigid-sphere gases (i.e. single-component, monatomic gases) we have shown that the use of higher-order Sonine polynomial expansions enables one to obtain results of arbitrary precision that are free of numerical error and, in a second paper (II), we have extended our initial simple gas work to modeling the viscosity in a binary, rigid-sphere, gas mixture. In this latter paper we reported an extensive set of order 60 results which are believed to constitute the best currently available benchmark viscosity values for binary, rigid-sphere, gas mixtures. It is our purpose in this paper to similarly report the results of our investigation of relatively high-order (order 70), standard, Sonine polynomial expansions for the diffusion- and thermal conductivity-related Chapman–Enskog solutions for binary gas mixtures of rigid-sphere molecules. We note that in this work, as in our previous work, we have retained the full dependence of the solution on the molecular masses, the molecular sizes, the mole fractions, and the intermolecular potential model via the omega integrals. For rigid-sphere gases, all of the relevant omega integrals needed for these solutions are analytically evaluated and, thus, results to any desired precision can be obtained. The values of the transport coefficients obtained using Sonine polynomial expansions for the Chapman–Enskog solutions converge and, therefore, the exact diffusion and thermal conductivity solutions to a given degree of convergence can be determined with certainty by expanding to sufficiently high an order. We have used Mathematica® for its versatility in permitting both symbolic and high-precision computations. Our results also establish confidence in the results reported recently by other authors who used direct numerical techniques to solve the relevant Chapman–Enskog equations. While in all of the direct numerical methods more-or-less full calculations need to be carried out with each variation in molecular parameters, our work has utilized explicit, general expressions for the necessary matrix elements that retain the complete parametric dependence of the problem and, thus, only a matrix inversion at the final step is needed as a parameter is varied. This work also indicates how similar results may be obtained for more realistic intermolecular potential models and how other gas-mixture problems may also be addressed with some additional effort. [Copyright &y& Elsevier]

Abstract: The Chapman–Enskog solutions of the Boltzmann equations provide a basis for the computation of important transport coefficients for both simple gases and gas mixtures. These coefficients include the viscosity, the thermal conductivity, and the diffusion coefficient. In a preceding paper (I), for simple, rigid-sphere gases (i.e. single-component, monatomic gases) we have shown that the use of higher-order Sonine polynomial expansions enables one to obtain results of arbitrary precision that are error free. It is our purpose in this paper to report the results of our investigation of relatively high-order, standard, Sonine polynomial expansions for the viscosity-related Chapman–Enskog solutions for binary gas mixtures of rigid-sphere molecules. We note that in this work we have retained the full dependence of the solution on the molecular masses, the molecular sizes, the mole fractions, and the intermolecular potential model via the omega integrals. For rigid-sphere gases, all of the relevant omega integrals needed for these solutions are analytically evaluated and, thus, results to any desired precision can be obtained. The values of viscosity obtained using Sonine polynomial expansions for the Chapman–Enskog solutions converge monotonically from below and, therefore, the exact viscosity solution to a given degree of convergence can be determined with certainty by expanding to sufficiently high an order. We have used Mathematica® for its versatility in permitting both symbolic and high precision computations. Our results also establish confidence in the results reported recently by other authors who used direct numerical techniques to solve the relevant Chapman–Enskog equations. While in all of the direct numerical methods more-or-less full calculations need to be carried out with each variation in molecular parameters, our work utilizes explicit, general expressions for the necessary matrix elements that retain the complete parametric dependence of the problem and, thus, only a matrix inversion at the final step is needed as a parameter is varied. This work also indicates how similar results may be obtained for more realistic intermolecular potential models and how other gas-mixture problems may also be addressed with some additional effort. [Copyright &y& Elsevier]

A steady flow of a vapor in a half space condensing at incidence onto a plane condensed phase is considered in the case where another gas that does not condense (the noncondensable gas) is present near the condensed phase. A systematic asymptotic analysis of the Boltzmann equation for hard-sphere molecules is performed in the case where condensation is weak, and the relation among the parameters of the vapor flow at infinity, those associated with the plane condensed phase, and the amount of the noncondensable gas is derived in an analytical form. The result supplements the numerical result for the relation for arbitrarily strong condensation obtained on the basis of a model Boltzmann equation and under the restriction that the vapor molecules are mechanically identical with the noncondensable-gas molecules [Taguchi et al., Phys. Fluids 15: 689 (2003)]. [ABSTRACT FROM AUTHOR]

We have performed simulations on a coplanar structured alternating current plasma display panel cell sustained in the ternary He-Ne-Xe gas mixture and its discharge characteristics were compared with those of the conventional binary Ne-Xe mixture, by using the two-dimensional fluid model simulator. Since plasma display panels use micro-discharges in the Xe mixed gas to generate vacuum ultraviolet light to excite phosphor for visible light emission, the condition of discharge gas mixtures is one of the main factors that determine luminous efficacy and thus, intensive studies on discharge gas mixture are essential to optimize it. As the He concentration increases in the He-Ne-Xe mixture, luminance and luminous efficacy increase but power consumption decreases, which agrees well with the recent experimental findings. We have found that the enhanced ion mobilities in the gas mixture by adding He gas to the conventional Ne-Xe mixture play an important role in increasing luminous efficacy of a plasma display panel cell, by reducing the cathode fall potential. In addition, He atoms increase the number of Xe*(3P2) in the excited state and thus, the dimer emission is increased while the resonant line is reduced with the He content. As a result, the total vacuum ultraviolet emission is increased and higher luminance and higher luminous efficacy can be obtained. [ABSTRACT FROM PUBLISHER]

Abstract: A Legendre expansion of the scattering kernel, a conservation condition and some exact solutions are reported for the McCormack kinetic model that is used to describe a binary mixture of rarefied gases. [Copyright &y& Elsevier]

Abstract: The present paper investigates a promising avenue for the intensification of turbulent free convection in various configurations using adequate binary gas mixtures in which helium (He) is the primary gas component and carbon dioxide (CO2), methane (CH4), nitrogen (N2), oxygen (O2) and xenon (Xe) are the secondary gas components. In the context of binary gas mixtures, the thermo-physical properties: viscosity, thermal conductivity, density and isobaric heat capacity depend on three quantities: temperature, pressure and molar gas composition. Within the platform of turbulent free convection using the five binary gas mixtures for Ra >109, results are presented for the allied convective coefficient h mix/B varying with the molar gas composition w in the w-domain [0, 1]. Values of the maximum allied convective coefficients h mix,max/B attained at the correlative optimal molar gas compositions w opt are easily extracted from suitable design charts. [Copyright &y& Elsevier]

Steady flows of a vapor with evaporation and condensation on the boundary consisting of the condensed phase of the vapor are considered in the following situation: (i) the boundary is of arbitrary smooth shape; (ii) the Knudsen number Kn, the ratio of the typical mean free path of the vapor molecules to the characteristic length of the system, is small; (iii) a small amount of a noncondensable gas is contained in the system; more specifically, the amount is such that the average concentration of the noncondensable gas is of the order of Kn in the case of a closed domain (the case of an infinite domain is also discussed). The steady behavior of the vapor and the noncondensable gas, in particular, that in the continuum limit where Kn vanishes, is investigated by means of a systematic asymptotic analysis based on kinetic theory. In this situation, the average concentration of the noncondensable gas becomes infinitely small in the continuum limit in the case of a closed domain. However, it is shown that the noncondensable gas accumulates in the infinitely thin Knudsen layer on the boundary where condensation is taking place and has a significant effect on the global vapor flow in the continuum limit. An example demonstrating such an effect is also given. [Copyright &y& Elsevier]

The structure of a shock wave for a binary gas mixture is studied on the basis of numerical solution of the complete kinetic Boltzmann equation for the model of hard sphere molecules. For the evaluation of the collision integral we apply a generalization of the conservative discrete ordinate method (the kernel method for a single gas was developed by Tcheremissine) for binary gas mixtures and for the case of cylindrical symmetry. The transition from up-stream to downstream uniform state is presented by macroscopic values and by distribution functions. [Copyright &y& Elsevier]

A binary gas mixture conductance measurement apparatus with an independent gas distribution system was established, the constant volume method to measure the conductance of the mixed gas was used. Also, the conductance of pure gas Ar, He, N 2 and binary gas mixtures Ar–He, N 2 –He, Ar–N 2 through a short tube under different gas distribution chamber pressures and different molar fractions were measured. Meanwhile, the equivalent single gas method was used to calculate the conductance of binary gas mixtures. To verify the accuracy of this method, the relative error between the calculated and the measurement was carried out. The result shows that the equivalent single gas method is suitable for a small Knudsen number (1 / K n ≥ 10), the molar fraction of lighter species is low and a small difference in the molecular mass of the components in the mixed gas. The uncertainty of conductance measurement is better than 3.1%. • A binary mixed gas conductance measurement apparatus with an independent gas distribution system was established. • The conductance of binary mixed gas at different G-D chamber pressures and different molar fractions was measured. • The equivalent single gas method was used to calculate the conductance of binary gas mixture. [ABSTRACT FROM AUTHOR]