Viscosity measurements of compressed liquid refrigerant blend R-507A, using a vibrating-wire technique

The refrigerant blend R-507A (50 wt % HFC-143a, 50 wt % HFC-125) is an azeotropic mixture of hydrofluorocarbon refrigerants, 1,1,1-trifluoroethane (HFC-143a) and pentafluoroethane (HFC-125). The paper reports viscosity measurements, performed with a vibrating-wire viscometer, of the refrigerant blend R-507A,at five temperatures in the range (253 to 293) K. The measurements were carried out at pressures from slightly above saturation up to 10 MPa, except for the isotherms at 253.26 K where the maximum pressure was 7.52 MPa and at 263.23 K where the maximum pressure was 7.09 MPa. The overall uncertainty of these measurements is estimated to be ( 1.0 %. The data obtained were correlated by means of a modified hard-sphere based correlation technique. The root-mean-square deviation, rmsd, of the experimental results from the correlation equations is 0.23 %, and their bias is not significant. This correlation method has also been used to interpolate and extrapolate the present results to enable comparisons with measurements performed by other authors of the viscosity of liquid R-507A at different temperatures and pressures

Viscosity measurements of compressed ionic liquid EMIM OTf

1ª edição do CQE Days, organizada pelo Centro de Química Estrutural, realizada na Academia das Ciências de Lisboa, de 30-31 de maio de 2019 - https://cqe.tecnico.ulisboa.pt/cqedaysIonic liquids have attracted considerable interest in recent years, as they can be used for multiple aims, namely, as antistatic agents, electrolytes, solvents, lubricants, and CO2 absorbents [1]. The use of ionic liquids in industrial processes require their thermophysical properties, in particular, the viscosity and the thermal conductivity. However, transport properties are scarce due to the difficulty of the measurements, particularly at pressures higher than the atmospheric pressure. Our group has developed a programme of measurements aiming at obtaining rigorous results for the viscosity of ionic liquids using the vibrating wire method. This technique, although very accurate for molecular, non-conducting liquids, could have some difficulties with ionic liquids due to their electrical conductivity [2]. As we were planning to use the vibrating wire method in the forced mode of oscillation, the method requires the acquisition of the frequency response of the wire in a range of frequencies containing the velocity resonance for the transverse oscillations of the wire. Therefore, it is important to verify if the ionic liquid sample is a good electrolytic conductor in the range of frequencies that matter for the measurement of viscosity. The problematic of measuring the viscosity of ionic liquids both in general and in particular, using the vibrating wire technique was studied [3]. Pardal et al. [4] have used 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIMOTf) mixed with water as the electrolyte to successfully reduce CO2 at high pressure. The objective of this work is to contribute with viscosity data in the pressure and temperature range of the work performed by those authors. Therefore, we present new ionic viscosity results for temperatures between 298 K and 347 K and pressures up to 50 MPa.N/

Studying the PEG family

1ª edição do CQE Days, organizada pelo Centro de Química Estrutural, realizada na Academia das Ciências de Lisboa, de 30-31 de maio de 2019 - https://cqe.tecnico.ulisboa.pt/cqedaysThe main goal of this line of research is the realisation of experimental measurements of thermophysical properties of a homologous series of ethylene and polyethylene glycols [H(OCH2CH2)nOH], and the development of correlation methods, with an accuracy adequate for the applications. Ethylene glycols and poly (ethylene) glycols (PEG) are widely used in many industrial applications as green solvents and as components of important sustainable processes as they are considered environmentally acceptable compounds [1,2]. Liquid Poly(ethyleneglycols) [PEGs] are in general considered as green solvents. They are non-volatile; their toxicity is very low, such that they are being used as food additives [3]. PEGs have been found to be biodegradable by bacteria in soil or sewage, but the ability of bacteria to biodegrade PEG decreases with increasing molecular weight [3]. The study of this series of compounds is important in many respects, not only because it is aimed at the study of PEGs which have innumerable practical applications but also because this study can be useful to monitor the degree of polymerization in the production of PEGs, themselves. In the present work, the viscosity of three ethylene glycols, namely diethylene, triethylene and tetraethylene glycols [4] and PEG 400 were measured with high accuracy using the vibrating wire technique at moderately high pressures. Complementary experimental density, surface tension and rheological behavior were obtained for the same liquids. One of the aims of the work is to analyse the relation of the present results with those obtained before for CO2 saturated PEG400 mixturesProject UID/QUI/00100/2013 and Project UID/QUI/00100/2019 funded by Fundação para a Ciência e a Tecnologia (FCT), Portugal.N/

Viscosity and density measurements on compressed liquid n-Tetradecane

Comunicação apresentada na "University of Technology", em Graz, Áustria de 3-8 de setembro de 2017FCT - Fundação para a Ciência e Tecnologiainfo:eu-repo/semantics/publishedVersio

On the viscosity and other properties of poly(Ethylene Glycol) 600

Poster da conferência realizada na "University of Technology", em Graz, Áustria de 3-8 de setembro de 2017info:eu-repo/semantics/publishedVersio

Quest for a reference standard for viscosity at high temperatures and high pressures

This communication is dedicated to give notice of the present situation concerning the proposal of tris(2-ethylhexyl) trimellitate (TOTM) to be a reference standard fluid for viscosity at high temperatures and high pressures. This proposal stems from an internal project of the International Association for Transport Properties (IATP). A general overview of the efforts carried out so far by the scientific community towards that objective will be made. This will be complemented by a description of its main characteristics that support its proposal. In particular, the present work is concerned with the determination of the shear dependence of the viscosity of TOTM. Moreover, new results for the density of TOTM at moderately high temperatures and pressures up to 70 MPa are presented.This work was supported by the Strategic Project PEstOE/QUI/UI0100/2013 funded by Fundação para a Ciência e a Tecnologia (FCT, Portugal).N/

Viscosity of Compressed Liquid 1,1,1-Trifluoroethane (HFC-143a) and Pentafluoroethane (HFC-125)

The viscosity of compressed liquid 1,1,1-trifluoroethane (HFC-143a) and pentafluoroethane (HFC-125) has been measured with a vibrating-wire viscometer at five temperatures between (254 and 293) K. The measurements were performed at pressures from above saturation up to 10 MPa, although for the isotherms at about 254 K the maximum pressure was approximately 5 MPa for HFC-143a and 7.4 MPa for HFC-125. For the isotherm at about 263 K, the highest pressure for HFC-143a was of the order of 7.5 MPa. The overall uncertainty of these results has been estimated to be less than ( 1.0 %. The measurements have been correlated using a scheme based on a hard-spheres model. The root mean square deviation of the experimental results from the correlations for HFC-143a and HFC-125 is ( 0.24 % and ( 0.25 %, respectively. The correlation scheme has been used to perform the small extrapolations of the present data to the saturation line to enable comparison with literature results at saturation pressure

Viscosity and density measurements on liquid n-heptadecane at high pressures

This article reports novel measurements of the viscosity, η, of liquid n-heptadecane at pressures up to 70 MPa, along six isotherms between 303 and 358 K. The experiments were carried out using a vibrating wire viscometer operated in the forced mode. The 303 and 313 K isotherms have a restricted range of pressures to avoid eventual solidification. The present measurements have an uncertainty less than U(η) = 0.015·η with a confidence level of 0.95. Complementary measurements of the density, ρ, were performed with the same ranges of temperature and pressure, using a DMA HP Anton Paar U-tube densimeter, with a DMA 5000 instrument as a reading unit. The overall maximum uncertainty is U(ρ) = 0.002·ρ with a confidence level of 0.95. The article provides a correlation of the viscosity of compressed liquid n-heptadecane with the molar volume, constructed by means of a scheme based on a modified hard-sphere theory, which describes the experimental data within ca. 1%. A program is provided in the Supporting Information to promptly perform interpolation of the viscosity as a function of temperature and pressure. The isothermal compressibility and the isobaric thermal expansivity were calculated from the density. Viscosity–pressure coefficients have also been determined from the viscosity.This work was supported by the Project UID/QUI/00100/2013 and Project UID/QUI/00100/2019 funded by Fundação para a Ciencia e a Tecnologia (FCT), Portugal. The authors ̂are grateful to FCT, Portugal, for its support.info:eu-repo/semantics/publishedVersio

Viscosity and density of two 1-alkyl-3-methyl-imidazolium triflate ionic liquids at high pressures: experimental measurements and the effect of alkyl chain length

New measurements of the viscosity of 1-butyl-3-methyl-imidazolium triflate ([BMIM][OTf]) and 1-hexyl-3-methyl-imidazolium triflate ([HMIM][OTf]) have been carried out at high pressures, using a vibrating-wire technique operated in the forced mode of oscillation. The measurements for [BMIM][OTf] have been performed along six isotherms from 298 to 358 K at pressures up to 50 MPa. The viscosity measurements for [HMIM][OTf] have been carried out along five isotherms from 303 to 358 K at pressures up to 50 MPa. The estimated uncertainty of the measurements is less than U(η) = 0.02·η for viscosities up to 68 mPa·s and less than U(η) = 0.026·η for higher viscosities, with a confidence level of 0.95 (k = 2). For both ionic liquids, complementary density measurements have been performed using an Anton Paar HP densimeter in the same temperature and pressure ranges as those used for the viscosity measurements. The density results have an uncertainty smaller than U(ρ) = 0.002·ρ with a confidence level of 0.95 (k = 2). The viscosity results were correlated with the density data using a previously described hard-sphere-based technique. The individual correlations are able to describe the viscosity results for each liquid with an uncertainty smaller than the estimated uncertainty of the experimental data. The effect of alkyl substituents on the viscosity and the density of these ionic liquids has been analyzed. For this purpose, previously published results for the viscosity and density of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) have been considered in addition to the data obtained in the present work for [BMIM][OTf] and [HMIM][OTf].Project UID/QUI/00100/ 2013 (Fundação para a Ciência e a Tecnologia (FCT)); Project UID/QUI/00100/2019 (Fundação para a Ciência e a Tecnologia (FCT)).info:eu-repo/semantics/publishedVersio

Viscosity measurements of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIM OTf) at high pressures using the vibrating wire technique

The goal of the present work is to contribute to the characterization of ionic liquids by measuring their viscosity at high pressures. As 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIM OTf) has been used as a solvent in CO2 capture processes, the temperature and pressure ranges of the measurements cover the intervals used in those processes. Measurements of the viscosity of EMIM OTf along five isotherms in the range (298–358) K and at pressures up to 50 MPa, have been performed using the vibrating wire technique in the forced mode of operation. As far as the authors are aware, these are the first measurements of this ionic liquid at pressures higher than 0.1 MPa, to be published. The viscosity results were correlated with the molar volume, using a modified hard-spheres model. The root mean square (σ) deviation of the data from the correlation is less than 0.5% The expanded uncertainty of the present viscosity data is estimated as ±2.0% at a 95% confidence level. As a complement, the pressure-viscosity coefficient has been calculated within the temperature range of the present results. Previous studies of the influence of the electric conductivity of ionic liquids, including EMIM OTf, in the vibrating wire method, have been taken into account for the present work. Complementary measurements of the density have been performed along seven isotherms in the temperature range from (298–363) K and pressures from (0.1–70) MPa. The density measurements were carried out with an Anton Paar vibrating U-tube densimeter and the raw data were corrected for viscosity effects. The density results were correlated with the temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density data is estimated as ±0.2% at a 95% confidence level.This work was supported by the Project UID/QUI/00100/2013 and Project 21 UID/QUI/00100/2019 funded by Fundação para a Ciência e a Tecnologia (FCT), Portugal. 22 The authors are grateful to FCT, Portugal, for its support.info:eu-repo/semantics/publishedVersio