Vapor–liquid equilibrium of the (water + ethanol + glycerol) system: Experimental and modelling data at normal pressure

In this work, vapor-liquid equilibrium data of the ethanol–water–glycerol system were measured in an Othmer-type ebulliometer at normal pressure. The choice for this system was due to the importance of the ethanol–water separation. The samples analyses were done in a digital densimeter, and the methodology was previously validated with data available in the literature. Since the mean relative deviation was less than 5% in temperature and vapor composition, new data from mixtures of ethanol–water–glycerol were obtained. The experiments showed that glycerol is a promising solvent to ethanol dehydration since it eliminates the azeotrope and promotes the production of anhydrous ethanol. A thermodynamic model for this system was developed using the NRTL model to describe the non-ideality of the liquid phase. The modeling results were compared with experimental data and the deviations were lower than 7%. In this way, the model developed in this work can be used for simulation of ethanol dehydration.     

New p–ρ–T measurements up to 70 MPa for the system CO2 + propane between 298 and 343 K at near critical compositions

The vibrating tube densimeter method along with the Forced Path Mechanical Calibration model, is used to measure the high pressure isothermal p–ρ behavior of the CO₂+propane system along 17 isotherms between 293 and 343 K, at pressures up to 70 MPa. The compositions cover the range of mole fractions from x_CO2=0.45 to 1.0. The uncertainty in temperatures is ±0.015 K. The uncertainties in pressures are ±0.0013 MPa from 0.1 to 15.0 MPa and ±0.010 MPa from 5.0 to 70.0 MPa. The precision of the density measurements is ±0.014 kg m⁻³. The minimum global uncertainty is ±0.204 kg m⁻³, based on the calibration of the densimeter with pure water. A generalized Helmholtz energy model for mixtures is used to check the consistency of the new data with respect to previous p–ρ–T studies of this mixture. The average absolute deviation of our data with respect to the model is 0.64% which is fully consistent with the assessed accuracy.     

Density determination of slush nitrogen by the improved capacitance-type densimeter

Slush nitrogen is considered to be a better coolant than subcooled liquid nitrogen for the high-temperature superconducting cable cooling because of its greater density and cooling capacity. The capacitance-type densimeter is utilized to determine the density of slush nitrogen in this paper. In order to improve the densimeter performance, the bulk shielding method, based on the application of the double-shielded cables, is introduced, and the influence of the frequency of the applied voltage is investigated. The parasitic capacitance of the densimeter system is significantly reduced, and the fluctuation of the capacitance is depressed within ±2.0 × 10⁻⁴ pF at a frequency of 1.0 MHz, and the typical sensitivity of the differential type densimeter is 3.718 pF and the high accuracy of within ±0.25% for density measurement is obtained. In process of producing slush nitrogen by the freeze-thaw method, the discharge rate is 4 l/s and the time of the freeze and thaw cycles is 10 s and 5 s respectively to obtain slush nitrogen with fine solid particles, and slush density is measured by the densimeter system. According to the experimental results, the rotating speed, higher than 50 rpm in this study, is necessary to homogenize slush nitrogen for the high accuracy of the density measurement.     

A fractional differential equation for a MEMS viscometer used in the oil industry

A mathematical model is developed for a micro-electro-mechanical system (MEMS) instrument that has been designed primarily to measure the viscosity of fluids that are encountered during oil well exploration. It is shown that, in one mode of operation, the displacement of the device satisfies a fractional differential equation (FDE). The theory of FDEs is used to solve the governing equation in closed form and numerical solutions are also determined using a simple but efficient central difference scheme. It is shown how knowledge of the exact and numerical solutions enables the design of the device to be optimised. It is also shown that the numerical scheme may be extended to encompass the case of a nonlinear spring, where the resulting FDE is nonlinear.     

浆氮电容式密度计及液位计的实验研究

采用电容式密度计及液位计来测量浆氮密度及液位的变化,使用整体屏蔽法对测量系统进行保护以减小寄生电容并提高其抗干扰能力。从理论上分析整体屏蔽法在提高测量系统性能上的作用,并通过实验加以验证。在实验中对密度计和液位计进行标定以提高其测量的精度,并使用密度计测量制备过程中浆氮密度的变化情况。     

Some Thermodynamic Properties of the Binary Systems of Toluene with Butyl Methacrylate,Allyl Methacrylate,Methacrylic Acid and Vinyl Acetate at 20, 30 and 40 °C

Densities of the binary systems of toluene with butyl methacrylate, allyl methacrylate, methacrylic acid, and vinyl acetate have been measured as a function of composition at 20, 30 and 40 °C at atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The excess molar volumes are negative for the system toluene + butyl methacrylate and positive for the three other binaries, and become more so as the temperature increases from 20 to 40 °C. The system toluene + allyl methacrylate presents near ideal behavior. The apparent volumes were used to calculate values of the partial excess molar volumes at infinite dilution. The excess coefficient of thermal expansion is positive for the four binary systems. The calculated excess molar volumes were correlated with the Redlich–Kister equation and with a series of Legendre polynomials. An explanation of the results is given based by the FT-IR (ATR) and ¹³C NMR spectra of equimolar mixtures of the different systems.     

Density, excess volume, and excess coefficient of thermal expansion of the binary systems of dimethyl carbonate with butyl methacrylate, allyl methacrylate, styrene, and vinyl acetate at T = (293.15, 303.15, and 313.15) K

Densities of the binary systems of dimethyl carbonate with butyl methacrylate, allyl methacrylate, styrene, and vinyl acetate have been measured as a function of the composition at (293.15, 303.15, and 313.15) K at atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The excess molar volumes are negative for the (dimethyl carbonate + vinyl acetate) system and positive for the three other binaries, and become more so as the temperature increases from (293.15 to 313.15) K. The apparent volumes were used to calculate the values of the partial excess molar volumes at infinite dilution. The excess coefficient of thermal expansion is positive for the four binary systems. The calculated excess molar volumes were correlated with the Redlich-Kister equation and with a series of Legendre polynomials. An explanation of the results is offered based on the FT-IR (ATR) spectra of several mixtures of the different systems.