Variable-volume Cell Research Articles

Bubble-point pressures and saturated- and compressed-liquid densities of the binary R-125 + R-143a system

Bubble-point pressures and saturated- and compressed-liquid densities of the binary R-125 (pentafluoroethane) + R-143a (1,1,1 -trifluoroethane) system have been measured for several compositions at temperatures from 280 to 330 K by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows. The experimental uncertainties of the temperature, pressure, density, and composition were estimated to be within ±10mK, ± 12 kPa, ±0.2%, and ±0.2mass%, respectively. The purities of the samples used throughout the measurements are 99.96 area% for R-125 and 99.94 area% for R-143a. Based on these measurements, the thermodynamic behavior of the vapor-liquid equilibria of this binary refrigerant mixture has been represented using the Peng–Robinson equation for the bubble-point pressures, a correlation for the saturated-liquid densities, and an equation of state for the compressed-liquid densities.

Liquid Densities of Propane + Linear Low-Density Polyethylene Systems at (354−378) K and (4.00−7.00) MPa

Liquid densities have been measured with a variable volume cell for propane + linear low-density polyethylene systems. The temperature and pressure ranges studied are (354−378) K and (4.00−7.00) MPa, and polyethylene mass fractions in the mixtures vary between 0 and 0.0355. Altogether, 107 liquid density data points are reported. The results obtained for pure propane agree well with literature values. Results show that densities increase almost linearly with increasing mass fraction of the polymer.

Equilibrium conditions for hydrate formation from binary mixtures of methane and carbon dioxide in the presence of electrolytes, methanol and ethylene glycol

Ethylene glycol, methanol and electrolytes inhibit hydrate formation. Computation of the inhibition effects of these additives is necessary for the design of industrial operations where it is desired to avoid hydrate formation. Development of thermodynamic methods to calculate the hydrate equilibria conditions requires accurate experimental data. In the present work experimental three phase (aqueous liquid solution, vapor and incipient solid hydrate) equilibrium data for two mixtures of methane and CO 2 in the presence of methanol, ethylene glycol and electrolytes were obtained. The experiments were carried out in the temperature range of 264–282 K and pressure range of 1.5–10.4 MPa. A ‘full view’ fixed volume sapphire cell used earlier to gather data on CO 2 by the authors was converted into a variable volume cell with the help of a movable piston to perform the experiments.

Bubble Point Pressures and Densities for the Binary Systems of Propane with Triacontane, Hexatriacontane, Tetracontane, Pentacontane, and Squalane at 353−373 K and 4.00−7.00 MPa

Bubble point pressures and densities were measured with a variable volume cell for the binary systems propane + triacontane (n-C30H62), + hexatriacontane (n-C36H74), + tetracontane (n-C40H82), + pentacontane (n-C50H102), and + squalane (C30H62, 2,6,10,15,19,23-hexamethyltetracosane). The densities were measured for compressed liquids or supercritical fluids in the one-phase region. The studied temperature and pressure ranges were 353−373 K and 4.00−7.00 MPa, respectively. The mass fractions of the long-chain alkanes varied between 0 and 0.0326. It was found that the densities of the mixtures increased almost linearly with the mass fractions of the heavy alkanes. The effects of all the long-chain alkanes on the density did not depend on molar mass. Bubble point pressures decreased only very slightly as the mass fractions of the long-chain alkanes increased.

Vapor−Liquid Equilibria and Densities for the System Butane + Hexacontane

Liquid and vapor phase compositions and densities have been measured with a variable volume cell for the binary system butane + hexacontane (n-C{sub 60}H{sub 122}). Data sets at 433.15 K, 438.15 K, and 453.15 K are presented and include measurements in the mixture critical region.

Bubble-point pressures and liquid densities of binary R-125 + R-143a System

Bubble-point pressures and saturated-liquid densities of the binary R-135 (pentafuoroethane) + R- 143a ( 1, 1, 1-trifluoroethane) system have been measured for several compositions at temperatures from 280 to 330 K by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows. The experimental uncertainties of the temperature, pressure. and density measurements and the composition determination were estimated to be within ±15 mK, ±13 k Pa, ±0.2%, and ±0.1 wt%, respectively. The purities of the samples used throughout the measurements are 99.98 wt% for R-125 and 99.0 mol % for R- 143a. Based on the present data, the thermodynamic behavior of the vapor-liquid equilibria of this binary refrigerant mixture has been evaluated by using the Peng-Robinson equation for the bubble-point pressures, and the modified Hankinson-Brobst-Thomson equation for the saturated-liquid densities. This was done to identify the optimized binary interaction parameters.

Chlorofluorohydrocarbon—alcohol mixtures: bubble pressures and saturated liquid molar volumes (experimental data and modeling)

A static apparatus, described elsewhere, fitted with a variable volume cell was used to obtain new data. Results are given at two temperatures for the 1,1,2-trichlorotrifluoroethane (C 2F 3Cl 3)—ethanol and 1,2-dichlorotetrafluoroethane (C 2F 4Cl 2)—ethanol binary systems and four temperatures for the 1,2-dichlorotetrafluoroethane—trifluoroethanol and monochlorodifluoromethane (CHF 2Cl)—trifluoroethanol binary systems. Solubility data are well represented with nonclassical mixing rules and temperature-dependent binary interaction parameters for all the cubic equations of state used. However, the Trebble—Bishnoi—Salim equation of state yields the best simultaneous representation of saturated liquid molar volumes

Bubble pressures and saturated liquid molar volumes of binary and ternary mixtures of chlorofluorocarbons and hydrochlorofluorocarbons

Laugier, S., Richon, D. and Renon, H., 1994. Bubble pressures and saturated liquid molar volumes of binary and ternary mixtures of chlorofluorocarbons and hydrochlorofluorocarbons. Fluid Phase Equilibria 93; 297-316. The aim of this paper is to present new data for refrigerant mixtures. Bubble pressures and saturated liquid molar volumes were measured at several temperatures for the following binary systems; chlorodifluoroethane-trichlorotrifluoroethane (R142b-R113) trifluoromethane-chlorodifluoromethane (R23–R22), trifluoromethane-dichlorotetrafluoroethane (R23-R114): and the ternary system; trifluoromethane-dichlorotetrafluoroethane-trichlorotrifluoroethane (R23-R114-R113) using a variable volume cell and static isothermal equilibrium method. Data modeling was performed using several cubic equations of state with the present data. The best performance to represent simultaneously vapor pressures and saturated liquid molar volumes of either binary or ternary mixtures was achieved by either the regular or the generalized Trebble-Bishnoï-Salim equation of state (1991).

Bubble curves and saturated liquid molar volumes for chlorofluorohydrocarbon-hydrocarbon mixtures. Experimental data and modeling

Vapor-liquid equilibria and liquid densities were obtained using a static apparatus fitted with a variable-volume cell which was described in detail by Valtz et al. (1). Results are given at four temperatures for the binary systems butane--1,2,2-trichlorotrifluoroethane, pentane--1,2-dichloro-1,1,2,2-tetrafluoroethane, hexane--1,2-dichloro-1,1,2,2-tetrafluoroethane, heptane--1,12-trichloro-1,2,2-trifluoromethane, heptane--1,2-dichloro-1,1,2,2-tetrafluoroethane, and benzene--1,2-dichloro-1,1,2,2-tetrafluoroethane and the ternary system 1,2-dichloro-1,1,2,2-tetrafluoroethane--1,1,2-trichloro-1,2,2-trifluoromethane--heptane. The best simultaneous representation of pressures and saturated liquid molar volumes at a given temperature and liquid composition for these mixtures is obtained using either the Patel-Teja or Trebble-Bishnoi-Salim equation of state (TBS EOS) in either their standard or generalized form (maximum deviation 0.7% in pressure and 3.1% in saturated liquid molar volume with the TBS EOS).

Near-critical and supercritical fluid densities of CO2-SF6 mixtures

Abstract Super, M.S., Beckman, E.J. and Enick, R.M., 1992. Near-critical and supercritical fluid densities of CO2-SF6 mixtures. Fluid Phase Equilibria, 86: 275-292 A recently proposed technique for the separation of the major recyclable thermoplastics incorporates the variable density of CO2-SF6 mixtures at mild temperatures and elevated pressures. Therefore, near-critical liquid and supercritical fluid densities of these mixtures were determined at temperatures between 294 K and 338 K and pressures up to 47 MPa. Mixtures containing SF6 mole fractions from 0.230–0.849 were used. The temperature-pressure conditions required to attain a specified density were determined in a high-pressure, variable-volume cell by isothermally compressing a fluid of known composition until a glass density float remained suspended in the fluid. The densities of the eight floats used in this study ranged from 900.0 to 1449.4 kg m−3. The results were correlated with the modified Lawal-Lake-Silberberg (MLLS) EOS, designed specifically for accurate near-critical liquid and supercritical fluid phase densities, the mean field lattice gas (MFLG) EOS and the Benedict-Webb-Rubin-Starling (BWRS) EOS. Both the MLLS and the MFLG equations had three adjustable parameters for mixture density correlations, while the BWRS had only one. Better results for mixture densities were obtained with the MLLS EOS, which yielded an average absolute pressure deviation (AAPD) of 4.49% at a specified temperature, density and composition. The AAPDs for the MFLG and the BWRS EOS were 7.07% and 7.64%, respectively.

Liquid Densities and Vapor Pressure of HCFC 225ca and HCFC 225cb

Abstract Saturated liquid densities and vapor pressures of HCFC 225ca and HCFC 225cb were measured at temperatures from 280 to 400 K by a magnetic densimeter coupled with a variable volume cell; 28 and 36 measurements were obtained, respectively. The experimental uncertainties in temperature, pressure, and density measurements were estimated to be not greater than ± 15 mK, ± 10 kPa, and ± 0.2 %, respectively. The purities of the samples used were 99.95 % for both fluids. Simple correlations for saturated liquid densities and vapor pressures were developed for both substances on the basis of the present measurements.

Bubble pressure and saturated liquid molar volumes of the propane (1)-dichlorotetrafluoroethane(2)-trichlorotrifluoroethane(3) ternary system and of the three corresponding binaries

An apparatus described previously has been used for the present measurements. It is based on a synthetic static method with a variable-volume cell. Results are given at different temperatures between 343 and 423 K for three binary mixtures: propane-dichlorotetrafluoroethane (C 3H 8-R114), propane-trichlorotrifluoroethane (C 3H 8-R113), dichlorotetrafluoroethane-trichlorotrifluoroethane (R114-R113), and the corresponding ternary propane-dichlorotetrafluoroethane-trichlorotrifluoroethane (C 3H 8-R114-R113). The two binaries with propane are well represented by a one-parameter δ ij Peng-Robinson equation of state to within less than 1% for pressures and 6%, without volume translation, for saturated liquid molar volumes. By using a volume translation, an improved volume representation, 2%, for the propane-dichlorotetra-fluoroethane system is achieved. For the third binary system, δ ij = 0 is the best choice (representation is within 0.6% for pressure and 2% for molar volumes through a volume translation). Use of values of the binary interaction parameters δ ij established for binary systems enables good prediction of ternary data (representation to within 1% for pressures and 3.8% for saturated molar volumes). Volume translation does not improve the representation of the ternary saturated liquid molar volumes because it does not do it for the propane-trichlorotrifluoroethane system.

Saturated liquid densities and bubble-point pressures of the binary HFC 152a+HCFC 142b system

Forty-eight sets of the saturated liquid densities and bubble-point pressures of the binary HFC 152a + HCFC 142b system were measured with a magnetic densimeter coupled with a variable-volume cell. The measurements obtained at four compositions, 20, 40, 60, and 80 wt%, of HFC 152a cover a range of temperatures from 280 to 400 K. The experimental uncertainties in temperature, pressure, density, and composition were estimated to be within ±15mK, ±20kPa, ±0.2%, and between −0.14 and ±0.01 wt% HFC 152a (−0.01 and + 0.14 wt% HCFC 142b), respectively. The purities of the samples were 99.9 wt% for HFC 152a and 99.8 wt% for HCFC 142b. A binary interaction parameter, k ij , in the Peng-Robinson equation of state was determined as a function of temperature for representing the bubble-point pressures. On the other hand, two constant binary-interaction parameters, k ij and l ij , were introduced into the mixing rule of the Hankinson-Brobst-Thomson equation for representing the saturated liquid densities.

Saturated liquid densities and bubble point pressures of the ternary HCFC-22/HFC-152a/HCFC-142b system

Maezawa, Y., Widiatmo, J.V., Sato, H. and Watanabe, K., 1991. Saturated liquid densities and bubble point pressures of the ternary HCFC-22/HFC-152a/HCFC-142b system. Fluid Phase Equilibria, 67: 203-212. Seventy-one data points for the saturated liquid density and bubble point pressure of the ternary system HCFC-22/HFC-152a/HCFC-142b were measured by a magnetic densimeter coupled with a variable-volume cell. The results of six different compositions of 20/20/60, 20/40/40, 20/60/20, 40/20/40, 40/40/20 and 60/20/20 wt.% cover a range of temperatures from 280 to 390 K. The experimental uncertainties in temperature, pressure, density and composition were estimated to be not greater than ±15 mK, ±20 kPa, ±0.2%, and between −0.17 and +0.01 wt.% HCFC-22 (between −0.12 and +0.06 wt.% HFC-152a and between −0.01 and +0.11 wt.% HCFC-142b) respectively. The purity of the samples was 99.97 wt.% for HCFC-22, 99.9 wt.% for HFC-152a and 99.8 wt.% for HCFC-142b. The bubble point pressures were reproduced satisfactorily well by the Peng-Robinson equation of state with the optimum binary interaction parameters, i.e. temperature-dependent k 13 and k 23, and temperature-independent k 12. The saturated liquid densities were reproduced reasonably well by the Hankinson-Brobst-Thomson equation with the optimum temperature-independent binary interaction parameters, k 12 , k 13 , k 23, l 12, l 13 and l 23.

Saturated liquid densities and bubble-point pressures of the binary HCFC 22 + HFC 152a system

Sixty-six values of saturated liquid density and bubble-point pressure for the binary HCFC 22 + HFC 152a system were measured using a magnetic densimeter coupled with a variable volume cell. The results for five different compositions, 10, 30, 50, 70 and 90 wt.% of HCFC 22, cover a temperature range of 280–380 K. The experimental uncertainties in temperature, pressure, density and composition measurements were estimated to be not greater than ±15 mK, ±20 kPa and ±0.3% and between −0.11 and +0.01 wt.%, respectively. The purity of the sample used was 99.97 wt.% for HCFC 22 and 99.9 wt.% for HFC 152a. The modified Rackett equation proposed by Spencer and Dannar and the Hankinson-Brost-Thomson equation are discussed on the basis of the present measurements. Vapor—liquid equilibrium calculations based on the Peng-Robinson equation of state are also discussed.

Liquid densities and vapor pressures of 1-chloro-1,1-difluoroethane (HCFC 142b)

In this paper, thirty-six saturated liquid densities of HCFC 142b (1-chloro-1,1-difluoroethane) are measured in a range of temperatures from 210 to 400 K. Twelve vapor pressures, from 320 to 400 K, and six compressed liquid PVT properties, from 320 to 360 K and of pressures up to 2 MPa, are also measured. All measurements were made by a magnetic densimeter coupled with a variable volume cell. The experimental uncertainties in temperature, pressure, and density were estimated to be not greater than [plus minus]15 mK, [plus minus]10 kPa, and [plus minus]0.2%, respectively. The purity of the sample used was 99.8 wt % or better. The simple correlation for the saturated liquid density of HCFC 142b was developed.

Liquid densities and vapor pressures of 1,1,2,2-tetrafluoroethane (HFC 134) and 1,1-dichloro-1-fluoroethane (HCFC 141b)

Saturated liquid densities and vapor pressures of HFC 134 and HCFC 141b were measured at temperatures from 200 to 400 K by a magnetic densimeter coupled with a variable volume cell. For HFC 134, 38 saturated liquid densities associated with the vapor pressures and 5 compressed liquid PVT properties at temperatures 280-400 K and pressures up to 2 MPa were measured. For HCFC 141b, 37 saturated liquid densities associated with the vapor pressures and 24 compressed liquid PVT properties were measured at the same ranges

Bubble pressures and saturated liquid densities of R 22 + R 114 mixtures in the range 310?400 K

The bubble pressures and saturated liquid densities of mixtures of R 22 and R 114 have been measured with a static and synthetic method with a variable-volume cell. The results for five different compositions (100, 75, 50, 25, and 0 mol% R 22) cover the temperature range from 310 to 400 K. The experimental data for both pure components are compared with literature data, showing the reliability of the present results. The system shows positive deviations from Raoult's law at temperatures below 340 K and the deviations increase with decreasing temperature. The 25 mol % R 22 mixture shows the maximum non-ideality.

Bubble pressures and saturated liquid molar volumes of binary and ternary refrigerant mixtures

All measurements have been performed with a static apparatus using a variable volume cell. The results are given at two temperatures for the [R114-FC75] system and four temperatures for the three systems [R23-R11], [R23-R22-R11], and [R23-R22-R114]. Experimental data of binaries are well representd by the one adjustable parameter Peng-Robinson equation of state involving a volume translation

Solubility of chlorophyllian pigments in supercritical carbon dioxide and ethane

Measurements of solubilities in supercritical carbon dioxide and in supercritical ethane of pure chlorophyll-a and of chlorophyllian pigments extracted from marine algae are described in this paper. Spectrofluorimetric measurements have been carried on under thermodynamic equilibrium conditions in a variable volume cell made of sapphire. In the investigated pressure range (10 to 20 MPa), the solubilities of chlorophylls in CO 2 and in C 2H 6, which are an increasing function of the pressure or of the density of the fluids, have been estimated.