The Solubility of Salicylic Acid in Supercritical Carbon Dioxide

The possibility of using the method of supercritical fluid extraction for purifying the product of synthesis of salicylic acid is revealed and confirmed experimentally. A continuous-flow experimental setup is used to investigate the solubility of salicylic acid and phenol in supercritical CO₂ and to purify the product of synthesis of salicylic acid at a temperature of 308 K in the pressure range from 7.8 to 12 MPa. The salicylic acid content of the resultant product conforms to the requirements of the State Pharmacopoeia.     

Solubility of supercritical carbon dioxide in polyethylene glycol 4000

We present the experimental results on the solubility of supercritical carbon dioxide in polyethylene glycol of molecular weight 4000, namely, the isotherms at T = 313, 323, and 333 K in the pressure range of P = 10–35 MPa. Based on the Sanchez–Lacombe lattice model, the results of solubility are described and the empirical parameters of the binary intermolecular interaction in the system of supercritical CO₂-polyethylene glycol 4000 are obtained.     

Results of investigation of the solubility of ice and water in compressed gases

Analysis is made of the experimental data available from the literature on the solubility of ice and water in various compressed gases in a wide range of temperature and pressure. A new formula is derived that relates the equilibrium concentration x_eq of steam in moist gas at preassigned temperature and pressure to the constants of the equations of state for condensed water and to the virial coefficients. This formula enables one to directly calculate the solubility of steam in compressed gas without using the previously suggested solution of the set of equations. The derived formula makes it possible to describe the entire array of experimental data in the range of parameters from 200 to 400 K and from 0.1 to 10 MPa with an error equal to or less than the experimental error     

Solubility of Hydrogen Sulfide in [bmim][PF<Subscript>6</Subscript>]

New experimental data are presented for the solubility of hydrogen sulfide in the ionic liquid 1-N-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) at five temperatures in the range (298–403) K at pressures up to 9.6 MPa. The ionic liquid [bmim][PF₆] is a good solvent for hydrogen sulfide. At 9 MPa the mole fraction H₂S in the liquid is about 0.7. The solubility is a strong function of temperature; at 2 MPa the solubility (mole fraction H₂S) decreases from about 0.84 at 298 K to about 0.2 at 403 K. The Krichevsky–Kasarnovsky equation was used to correlate the experimental data, and Henry’s constants were obtained. The solution thermodynamic properties at standard temperature and pressure were calculated.     

Viscosity of Gaseous HFC-143a (1,1,1-trifluoroethane) Under High Pressures

The viscosity of gaseous HFC-143a(1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature under subcritical conditions or up to 9 MPa under supercritical conditions. Intermolecular potential parameters of HFC-143a for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation as functions of temperature and density is proposed to interpolate the present experimental results.     

New Data on the Solubility of Inert Gases in Liquid Alkali Metals at High Temperature

The solubility of helium, neon, argon, krypton, and xenon in molten lithium, sodium, potassium, rubidium, and cesium is calculated in the ranges of temperature from 600 to 1500 K and pressure from 0.1 to 10 MPa. The calculated data are compared, in comparable ranges of the parameters of state, with the results of the experimental investigations available in the literature of the solubility of inert gases in liquid alkali metals.     

The solubility of helium and argon in liquid lead,bismuth, and their eutectic alloy at high temperatures

The “hole” model is used to calculate the solubility of inert gases of helium and argon, in heavy liquid-metal coolants of fast nuclear power reactors, such as lead, bismuth, and lead-bismuth eutectic, at temperatures up to 1000 K and pressure of 0.1 MPa. The relative error of the resultant calculation data is estimated.     

ZSM-5沸石分子筛的高压吸附储氢特性

研究了ZSM-5沸石分子筛对氢的超临界吸附特性．结果表明，在77K／5MPa、195K／7MPa、293K／7MPa条件下，ZSM-5沸石分子筛的储氢质量分数分别为1．97％、0．65％和0．4％．用Clausius-Clapeyron方程求得的等量吸附热（3．8kJ／mol）与吸附量无关，表明该分子筛是一种表面势场均匀的吸附剂．将表面过剩吸附理论与描述Ⅰ型等温线的诸理论模型结合，分析了超临界吸附等温线，发现基于Toth方程的等温线模型在整个实验范围内与实验数据吻合较好，由该模型计算出的氢吸附相密度在77K达到55．6kg／m^3．根据回归参数讨论了超临界条件下氢在微孔沸石分子筛中的吸附机理，确认了氢在微孔沸石分子筛中的吸附为物理吸附．     

The thermal diffusivity of argon in the critical region

In this paper experimental results on the thermal diffusivity of argon in the supercritical region are reported. Five isotherms were investigated at 150.90, 153.16, 163.15, 173.14, and 188.14 K, in the pressure range from 2 to 13 MPa, corresponding to density variations from 90 to 800kg · m^–3. The experimental thermal diffusivity data are compared with theoretical predictions. The corresponding thermal conductivity coefficients are calculated and correlated with respect to the spinodal curve.     

低温下接触界面热阻的实验与模拟研究

在20-300 K和1.20-4.28 MPa范围内,分析温度和加载压力对铜-不锈钢接触界面热阻的影响,并进行回归分析和仿真研究.完全二次型模型与铜-不锈钢接触热阻实验结果吻合较好,最大相对误差为7％.仿真结果表明,在温度低于150 K时温度和压力的耦合对接触热阻的影响比较明显.     

Experimental investigation on heat transfer characteristics of supercritical CO2 cooled in horizontal helically coiled tube

An experimental investigation on the heat transfer characteristics of supercritical CO₂ during gas cooling process in a helically coiled tube is conducted. The experimental data are obtained over a mass flux range of 79.6–238.7 kg m⁻² s⁻¹, an inlet pressure range of 7.5–9.0 MPa and a mean bulk temperature of 23.0–53.0 °C. The effects of mass flux, bulk temperature and pressure on the heat transfer coefficient for helically coiled tubes are investigated. A comparative analysis of the gravitational buoyancy and the heat transfer coefficient is carried out between helically coiled tubes and straight tubes. A new heat transfer correlation of the supercritical CO₂ in the horizontal helically coiled tube is proposed based on the experimental data. The maximum error between the predicted results of the new correlation and the experimental data is 20%.     

Equation of State for the Thermodynamic Properties of 1,1,2,2,3-Pentafluoropropane (R-245ca)

An equation of state for the calculation of the thermodynamic properties of 1,1,2,2,3-pentafluoropropane (R-245ca), which is a hydrofluorocarbon refrigerant, is presented. The equation of state (EOS) is expressed in terms of the Helmholtz energy as a function of temperature and density, and can calculate all thermodynamic properties through the use of derivatives of the Helmholtz energy. The equation is valid for all liquid, vapor, and supercritical states of the fluid, and is valid from the triple point to 450 K, with pressures up to 10 MPa. Comparisons to experimental data are given to verify the stated uncertainties in the EOS. The estimated uncertainty for density is 0.1 % in the liquid phase between 243 K and 373 K with pressures up to 6.5 MPa; the uncertainties increase outside this range, and are unknown. The uncertainty in vapor-phase speed of sound is 0.1 %. The uncertainty in vapor pressure is 0.2 % between 270 K and 393 K. The uncertainties in other regions and properties are unknown due to a lack of experimental data.     

Thermodynamic behavior of supercritical fluid mixtures

The recent surge of interest in supercritical extraction has brought the unusual properties of supercritical mixtures into the focus of attention. We discuss some of the properties of binary mixtures in a range around the gas-liquid critical line from the point of view of supercritical solubility. The general thermodynamic relationships that govern the enhancement of supercritical solubility are readily derived by a mathematical method introduced by Ehrenfest. The enhancement is governed by a strong divergence centered at a critical end point. We give the classical and nonclassical power-law behavior of the solubility along the experimental paths of constant temperature or pressure. The factor multiplying the strong divergence contains the partial molar volume or enthalpy of the solute in the supercritical phase. These partials are quite anomalous, especially if the mole fraction of the solute is small. They diverge at the solvent's critical point. We cite experimental evidence of these divergences, especially the results of recent experiments in dilute near-critical salt solutions. The anomalies found in these salt solutions are common to all dilute near-critical mixtures with a nonvolatile second component. We show that on experimentally convenient paths the solubility in a binary liquid mixture near its consolute points is not strongly enhanced. Finally, we sketch a nonclassical model based on the decorated lattice gas that can be used to describe supercritical solubility enhancement at low solubility, with the pure solvent used as a reference.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

The Calculation of Equilibrium Concentrations of Organic Substances in Supercritical Fluids

The Peng-Robinson equation of state is used to construct a model of solubility of high-molecular hydrocarbons in supercritical fluids. The excess Gibbs energy of solution is used to estimate the coefficients in mixture rules. This approach enables one to self-consistently correct the coefficients in the mixture rules depending on the concentration of the solute, temperature and pressure. The calculation results are compared with the experimental data. The solubility of fatty acids in supercritical carbon dioxide is estimated.     

Viscosity of Gaseous HCFC-123 (2,2-Dichloro-1,1,1-Trifluoroethane) in the Temperature Range from 323.15 to 423.15 K and at Pressures up to 2 MPa

The viscosity of gaseous HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 323.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature in subcritical conditions or up to 2 MPa under supercritical conditions.     

Correlations for the viscosity of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E))

Due to concerns about global warming, there is interest in 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) as potential replacements for refrigerants with high global warming potential (GWP). In this paper we survey available data and provide viscosity correlations that cover the entire fluid range including vapor, liquid, and supercritical regions. The correlation for R1234yf is valid from the triple point (220 K) to 410 K at pressures up to 30 MPa, and the correlation for R1234ze(E) is valid from the triple point (169 K) to 420 K at pressures up to 100 MPa. The estimated uncertainty for both correlations at a 95% confidence level is 2% for the liquid phase over the temperature range 243 K to 363 K at pressures to 30 MPa, and 3% for the gas phase at atmospheric pressure.     

Measurements of the viscosity of compressed gaseous and liquid nitrogen + methane mixtures

The shear viscosity coefficients of three compressed gaseous and liquid nitrogen + methane mixtures have been measured at temperatures between 100 and 300 K and at pressures to about 30 MPa (4350 psia) with a piezoelectric quartz crystal viscometer. The precision of the measurements ranges from about 0.5% at high densities to about 1% at low densities. The estimated experimental error ranges from about 2% at high densities to about 4% at densities near the critical density and at supercritical temperatures near the critical temperature. The measurements have been compared with an extended corresponding states model, previously proposed for calculating the viscosities of fluid mixtures. Differences between the measured and calculated viscosities are discussed.     

Viscosity of Gaseous HFC-125 (Pentafluoroethane) Under High Pressures

This paper reports experimental results lor the viscosity of gaseous HFC-125 (pentafluoroethane) under high pressures. The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressures at each temperature at subcritical conditions or up to 9 MPa at supercritical temperatures. Intermolecular scaling parameters of HFC-125 for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation is proposed to interpolate the present experimental results as a function of temperature and density.     

模拟超临界氦迫流冷却系统

为ＣＩＣＣ子缆及子缆接头试验而设计的超临界氦迫流冷却系统由高压氦气钢瓶,汇流排,减压阀,流量控制阀,换热器等部件组成。