Binary Vapor Mixtures Research Articles

A combined ultrasonic flow meter and binary vapour mixture analyzer for the ATLAS silicon tracker

We describe a combined ultrasonic instrument for gas flow metering andcontinuous real-time binary gas composition measurements. The combinedflow measurement and mixture analysis algorithm employs sound velocitymeasurements in two directions in combination with measurements of thepressure and temperature of the process gas mixture.The instrument has been developed in two geometries following extensivecomputational fluid dynamics studies of various mechanical layouts. Aversion with an axial sound path has been used with binary gas flows upto 230 l.min−1, while a version with a sound path angled at45° to the gas flow direction has been developed foruse in gas flows up to 20000 l.min−1.The instrument with the axial geometry has demonstrated a flowresolution of ⩽ 1 % of full scale for flows up to 230 l.min−1and a mixture resolution of 3.10−3 for C3F8/C2F6 molar mixtures with ∼ 20 %C2F6. Higher mixture precision is possible in mixtures ofgases with widely-differing molecular weight (mw): a sensitivity of < 5.10−5 to traces of C3F8 in nitrogen (mw difference 160)has been seen in a long duration ( > 1yr) continuous study.A prototype instrument with 45° crossing angle hasdemonstrated a flow resolution of 1.9 % of full scale for linear flowvelocities up to 15 ms−1.Although this development was motivated by a requirement of the ATLASsilicon tracker evaporative fluorocarbon cooling system, the developedinstrument can be used in many applications where continuous knowledgeof binary gas composition is required. Applications include theanalysis of hydrocarbons, vapour mixtures for semi-conductormanufacture and anaesthetic gas mixtures.

Stability of a condensing liquid film in a binary vapor mixture system

We study stability of a condensing liquid film of a binary vapor mixture. When a binary vapor mixture of some kind is cooled on a substrate, a condensing liquid film emerges to take an inhomogeneous form such as a droplet one due to the solutal Marangoni effect. In order to analyze this phenomenon, we apply the long-wave approximation to the condensing liquid film and derive a nonlinear partial differential equation describing the spatio-temporal evolution of the film thickness. An interfacial boundary condition taking account of an effect of mass gain of the liquid film is adopted. Based on this model, we perform a linear stability analysis around a flat-film solution. We obtain an evolution equation of the amplitude of a disturbance, from which the cutoff and fastest growth wavenumbers are deduced. The maximum value of the cutoff wavenumber relative to the film thickness and its film thickness are estimated for water–ethanol mixture at atmospheric pressure. We numerically verify the long-wave nature of the instability of the condensate liquid film in this system. A significant difference in their values is found for low-ethanol fractions of the ambient vapor whether or not the temperature dependence of the mass transfer coefficient is considered. The wavenumber of a pattern of the liquid film observed in the experiment has the same parameter dependence as that of the fastest growth wavenumber.

Exergoeconomic analysis and optimization of a condenser for a binary mixture of vapors in organic Rankine cycle

Organic Rankine cycle (ORC) is a promising technology for converting low-grade waste heat into the electricity. This paper carries out an exergoeconomic analysis and performance optimization of a condenser for a binary mixture of vapors in the ORC system. In this model, the exergy loss due to heat transfer between a binary mixture of vapors and the cold fluid is taken into account and other exergy losses such as pressure drop and flow imbalance are ignored. The objective function is defined as the annual total cost per unit heat transfer rate considering the capital cost and the exergy loss cost. The variation laws of the annual total cost with the number of the transfer unit and the temperature ratios are exhibited. The optimal values of the number of the transfer unit and the heat capacity ratio which minimize the annual total cost have been obtained. The effects of related technical and economical parameters on the optimal performances have also been discussed.

Thermal effects accompanying stationary binary condensation of vapors into overcritical droplet

A set of equations is derived to calculate the stationary temperature and concentration of a solution in a overcritical droplet with regard to the heat release accompanying the condensation of a binary mixture of vapors in a diffusion or free-molecular regime. In the approximation of an ideal solution, relations are found for the stationary temperature of droplet growing under the conditions of strong and weak thermal effects. For the general case and the cases of strong and weak thermal effects, the temperature and concentration of the droplet and the coefficient of the thermal deceleration of the droplet growth are calculated as functions of the density of a passive gas. The influence of the condensation heat values of the first and second components of the mixture on the stationary temperature and concentration of the solution in the growing droplet is investigated separately.

Dynamics of variations in size and composition of supercritical droplet at binary condensation

A general analytical solution is found in quadratures for the radius and concentration of a solution droplet, which isothermally grows or evaporates in a diffusion or free-molecular regime in a binary mixture of vapors. The obtained solution describes the dynamics of variations in the size and composition of a super-critical droplet during the binary condensation in mixed vapors at an arbitrary initial droplet composition. It is shown that, at small (linear) deviations of the growth regime and droplet composition from the stationarity, these quadratures lead to the results that were recently obtained for the composition relaxation in a growing droplet. Moreover, it is demonstrated that, in terms of the nonlinear theory, when the deviation of solution concentration in a droplet from its stationary value is not small, it is invalid to use the law of stationary variations in the size of a droplet with time to describe the relaxation process for its chemical composition.

The viscosity of the binary vapor mixture methanol–triethylamine at low densities and in the saturated vapor phase of the vapor–liquid equilibrium

For the first time, results of precision measurements of the viscosity coefficient of the binary vapor mixture methanol–triethylamine at low densities are reported. The relative measurements with an all-quartz oscillating-disk viscometer were carried out for nearly equimolar mixtures along five isochores at densities from 0.010 to 0.033moldm−3 as well as for a mixture of the mole fraction ymeth=0.3322 at a density 0.016moldm−3 in the temperature range between 298 and 498K. The uncertainty is estimated to be ±0.2% at ambient temperature, increasing to ±0.3% at higher temperatures. Isothermal values of a mixture with the averaged mole fraction ymeth=0.5002 were recalculated from the original experimental data and evaluated with a first-order expansion for the viscosity, in terms of density. A so-called individual correlation on the basis of the extended theorem of corresponding states was employed to describe the interaction viscosity in the limit of zero density. Some data points at low temperatures had to be excluded from this calculation, since the measurements were performed in the saturated vapor phase. For these data points the vapor–liquid equilibrium had to be evaluated to assign the correct mole fraction in the vapor to the measured viscosity.

Measuring the transient diffusion of vapor mixtures through dense membranes

Abstract We propose a method of measuring the transient diffusion of vapor mixtures through flat dense membranes. The experimental setup consists of a self-developed differential permeation cell and a real-time analyzer to monitor the permeate–sweep gas mixture. The selectivity and the low sampling period of the real-time analysis are ensured by combining a quadrupole mass spectrometer and a gas chromatograph equipped with an inert capillary column. The proposed method is demonstrated at 298 K on the following binary mixtures of vapors: p -xylene–octane and toluene–octane permeating through low density polyethylene, and propan-1-ol–butan-1-ol vapors permeating through polydimethylsiloxane and through polydimethylsiloxane filled with montmorillonite. Based on extended Fick’s laws, we evaluate parameters describing cross-diffusion effects, using the Gauss–Newton method and finite difference modeling. In contrast to the transient diffusion of pure compounds, the simultaneous diffusion of a binary mixture of vapors is influenced by the dynamics of each diffusing compound. The effect on the transient diffusion of each vapor can be either positive or negative, depending on the type of membrane and on the actual mixture of vapors. Moreover, this cross-effect is mitigated by the presence of a filler, specifically of montmorillonite in polydimethylsiloxane in this particular case.

Vapor-phase adsorption of a mixture of benzene and chlorobenzene on the carbon adsorbent obtained by pyrolysis of hypercrosslinked polystyrene

Adsorption of a mixture of benzene and chlorobenzene from the gas phase on the carbon adsorbent D4609 (Purolite Int.) obtained by the pyrolysis of hypercrosslinked polystyrene was studied. The adsorption of the binary vapor mixture is satisfactorily described in terms of the theory of ideal adsorption solution. Specific features of the adsorption behavior of mixtures on this adsorbent are discussed.

Limits of Recognition for Binary and Ternary Vapor Mixtures Determined with Multitransducer Arrays

The discrimination of simple vapor mixtures from their components with polymer-coated multitransducer (MT) arrays as a function of the absolute and relative concentrations of those components is explored. The data set consists of calibrated responses to 11 organic vapors from arrays of 5 or 8 microsensors culled from a group of 5 cantilever, 5 capacitor, and 5 calorimeter transducers coated with 1 of 5 different sorptive-polymer films. Monte Carlo methods are applied to simulate error-enhanced composite responses to all possible binary and ternary mixtures of the 11 vapors, and principal component regression models are established for estimating expected rates of recognition as a function of mixture composition. The limit of recognition (LOR), defined as the maximum recognizable mixture composition range, is used as the metric of performance. With the optimal 8-sensor MT array, 19 binary and 3 ternary mixtures could be identified (i.e., discriminated from their components) with <5% error. The binary-mixture LORs are shown to decrease with increases in the baseline noise levels and random sensitivity variations of the sensors, as well as the similarity of the vapors. Importantly, most of the binary LOR contours are significantly asymmetric with respect to composition, and none of the mixtures could be recognized with <5% error at component relative concentration ratios exceeding 20:1. Discrimination of ternary mixtures from their components and binary subcomponent mixtures is possible only if the relative concentration ratio between any two of the components is <5:1. In comparing binary LORs for the best five-sensor single-transducer (ST) array to those of the best five-sensor MT array, the latter were larger in nearly all cases. The implications of these results are considered in the context of using such arrays as detectors in microanalytical systems with upstream chromatographic modules.

Binary Mixtures of Chlorobenzene and Cyclohexane Vapours Adsorbed under Dynamic and Static Conditions by Activated Carbon Beds

The adsorption of mixtures of chlorobenzene (C6H5Cl) + cyclohexane (c-C6H12) onto activated carbon U-03 has been examined at about room temperature. As shown by Stoeckli et al. (2002), combination of the Myers-Prausnitz-Dubinin theory (MPD) with the activity coefficients of the corresponding solid-liquid equilibrium led to a good correlation between the calculated and experimental mole fractions for the adsorption of binary mixture vapours by microporous solids under static conditions. The present study demonstrates the approach, which is based on an ideal adsorbed state (IAS).This can be employed for binary vapour mixtures such as chlorobenzene + cyclohexane under dynamic conditions in PSA (Pressure Swing Adsorption) and dynamic breakthrough experiments.

Evaporation and condensation of a binary mixture of vapors

AbstractHalf‐space problem of evaporation and condensation of a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard‐sphere molecules with the complete condensation condition. The problem is analyzed numerically by a finite‐difference method, in which the complicated collision integrals are computed by the extension of the method proposed by Y. Sone, T. Ohwada, and K. Aoki [Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps caused by the evaporation and condensation are constructed for arbitrary values of the concentration of the background reference state by the use of the Chebyshev polynomial approximation. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Half-space problem of the nonlinear Boltzmann equation for weak evaporation and condensation of a binary mixture of vapors

The half-space problem of evaporation and condensation of a binary mixture of vapors is investigated on the basis of the kinetic theory of gases. Assuming the Mach number of the normal component of the flow is small, a solution of the Boltzmann equation that varies slowly in the scale of the molecular mean-free-path (slowly varying solution) is introduced. Then a fluid-dynamic system that describes the behavior of the slowly varying solution is derived by a systematic asymptotic analysis. The analytical expression of the conditions allowing steady evaporation or condensation is derived from that system. We analyze the qualitative difference between the conditions in the evaporation and condensation cases: four conditions are needed in the former case while only one condition is required in the latter case. The present paper extends a earlier contribution of the first author for the BGK-type model equation [S. Takata, Half-space problem of weak evaporation and condensation of a binary mixture of vapors, in: Capitelli M. (Ed.), Rarefied Gas Dynamics, AIP, New York, 2005, pp. 503–508] to the Boltzmann equation. The extension is achieved by considering the linear stability of the far field in the case of evaporation and the H theorem, the monotonic decrease of the flux of Boltzmann's H function, in the case of condensation.

Temperature, pressure, and concentration jumps for a binary mixture of vapors on a plane condensed phase: Numerical analysis of the linearized Boltzmann equation

The half-space problem of the temperature, pressure, and concentration jumps for a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard-sphere molecules with the complete condensation condition. First, the problem is shown to be reduced to three elemental ones: the problem of the jumps caused by the net evaporation or condensation, that caused by the gradient of temperature, and that caused by the gradient of concentration. Then, the latter two are investigated numerically in the present contribution because the first problem has already been studied [Yasuda, Takata, and Aoki, Phys. Fluids 17, 047105 (2005)]. The numerical method is a finite-difference one, in which the complicated collision integrals are computed by the extension of the method proposed by Sone, Ohwada, and Aoki [Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps are constructed for arbitrary values of the concentration of the background reference state by the use of the Chebyshev polynomial approximation. The solution of the corresponding problem of a vapor-gas mixture and that of the temperature-jump problem on a simple solid wall are also obtained as special cases of the present problem.

Interfacial convection during evaporation of binary mixtures from porous obstacles

AbstractA novel experimental approach is proposed to investigate the influence of interfacial convection on liquid‐side mass transfer. Specifically, a binary liquid mixture (water and isopropanol) is evaporated from a porous obstacle into inert gas (air). The change of liquid bulk molar fraction with changing amount of liquid (concentration curve) is observed. The porous obstacle is a plate with parallel planar gaps, or a packed bed of spherical particles, both completely filled with the liquid. Without interfacial convection, that is, for the undisturbed state of the system, the liquid is quiescent and evaporation should be nonselective. Consequently, measured selectivities not only prove the existence of interfacial convection, but also give the opportunity of evaluating liquid‐side mass transfer coefficients and enhancement factors for the disturbed state of the system. This evaluation is conducted with the help of a one‐dimensional model for mass and heat transfer. If applied to the undisturbed state of the system, the same model provides driving density and molar fraction differences in the form of Rayleigh and Marangoni numbers. It is shown that the extent of interfacial convection can be controlled by operating parameters such as the gas bulk temperature, whereas it also depends on structural parameters such as gap width or particle diameter. Thermally driven and molar fraction driven Rayleigh and Marangoni convection may coexist. With the described method much higher enhancement factors than ever previously reported could be detected. The dependency of such enhancement factors on the Rayleigh or Marangoni number is considerably stronger than reported in the literature. Some aspects concerning the consideration of liquid‐side heat transfer or permeability and structure of the medium are discussed, and nonselective experiments corresponding to stable configurations are identified. First attempts toward correlation of the results are outlined, along with the potential of the method for future research. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Evaporation and condensation of a binary mixture of vapors on a plane condensed phase: Numerical analysis of the linearized Boltzmann equation

Half-space problem of evaporation and condensation of a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard-sphere molecules with the complete condensation condition. The problem is analyzed numerically by a finite-difference method, in which the complicated collision integrals are computed by the extension of the method proposed by Y. Sone, T. Ohwada, and K. Aoki [“Temperature jump and Knudsen layer in a rarefied gas over a plane wall: Numerical analysis of the linearized Boltzmann equation for hard-sphere molecules,” Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps caused by the evaporation and condensation are constructed for arbitrary values of the concentration of the background reference state by the use of the Chebyshev polynomial approximation.

Characteristic curves and the promotion effect of ethanol addition on steam condensation heat transfer

Although most previous studies concerning the condensation of binary vapor mixtures report the condensation rates to be less than that for pure vapor, heat transfer enhancement can be realized by using additives to form a positive system (solutal Marangoni condensation). The objective of the present study was to clarify the effect of mixing ethanol into steam on condensation heat transfer. Precise measurements of the ethanol concentration in the vapor of water–ethanol mixtures were performed over a wide range of ethanol concentrations, and the condensation behavior was observed. The maximum heat transfer coefficients in the condensation characteristic curves were determined to be 0.12 and 0.18 MW/m 2 K for vapor velocities of 0.4 and 1.5 m/s, respectively, and appeared at an ethanol vapor mass fraction of approximately 1%. The mixing was demonstrated to be extremely effective, particularly in the low-ethanol concentration range. The condensation heat transfer was enhanced approximately 2–8 times compared to pure steam.

Qualitative and quantitative analysis of organophosphorus pesticide residues using temperature modulated SnO 2 gas sensor

Qualitative and quantitative analysis of organophosphorus pesticide residues (acephate and trichlorphon) using temperature modulated SnO 2 gas sensor were studied. The testing method employed only a single SnO 2-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of pure pesticide vapor and a binary vapor mixture in the air. Experimental results showed that in the range 250–300 °C and at the modulating frequency of 20 mHz the high selectivity of the sensor could be achieved. The quantitative analysis of the pure pesticide vapor and their mixture were performed by fast Fourier transformation (FFT). The higher harmonics of the FFT characterized the non-linear properties of the response at the sensor surface. The amplitudes of the higher harmonics exhibited characteristic variations that depend on the concentration and the kinetics of pesticide species on the sensor surface.

Dependence of Separation Characteristics of Pervaporation on Parameters of Membranes Composed of Cellulose Myristinate and Polyphenylene Oxide

Experimental data on evaporation of binary mixtures composed of ethanol and water, ethyl acetate and acetic acid, water and acetic acid, and ethyl acetate and water in a wide range of concentrations, across film membranes composed of cellulose myristinate and polyphenylene oxide are presented.

平面凝縮相における2成分混合蒸気の蒸発・凝縮 : 線形化ボルツマン方程式の数値解析(S27-2 熱流体現象に対する分子気体力学および分子動力学法の応用(2),S27 熱流体現象に対する分子気体力学および分子動力学法の応用)

Half-space problem of evaporation and condensation of a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard-sphere molecules with the complete condensation condition. The problem is analyzed numerically by a finite-difference method, in which the complicated collision integrals are computed by the extension of the method proposed by Sone, Ohwada, and Aoki [Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps caused by the evaporation or condensation are constructed for arbitrary values of the concentration of a component gas by the use of the Chebyshev polynomial approximation.

Marangoni Instability in Evaporation of Binary Mixtures

The Marangoni instability is considered, which emerges in evaporation of binary mixtures and is related to the dependence of the surface tension on the composition of a mixture. The dispersion equation, which describes the development of hydrodynamic perturbations in the supercritical region, is derived in a linear approximation with respect to perturbations and with an exact undisturbed profile of the composition of the mixture in the surface region.