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- Viscosity of liquid diethylene, triethylene and tetraethylene glycols at moderately high pressures using a vibrating wire instrumentPublication . Pereira, Marta F. V.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando; Fareleira, JoãoNew viscosity measurements of compressed liquid diethylene glycol (DiEG), triethylene glycol (TriEG) and tetraethylene glycol (TeEG) have been performed using a vibrating wire instrument operated in the forced oscillation mode. The measurements have been carried out in a range of pressures up to 70 MPa and temperatures from (293-363) K, covering a total range of viscosities from (3.46-1.15 x 10(2)) mPa.s. Complementary experimental density data were obtained for the same glycols using an Anton Paar vibrating U-tube densimeter. These measurements have been performed in a range of temperatures from about (283-363) K and at pressures up to about 70 MPa. The viscosity results were correlated with density, using a modified hard-spheres scheme. The experimental density data were correlated, as a function of temperature and pressure, with a modified Tait-type equation. The expanded uncertainty of the present viscosity results at a 95% confidence level is estimated to be less than +/- 2.0% for viscosities up to 68 mPa s and less than +/- 2.6% for higher viscosities. The densities have an expanded uncertainty of +/- 0.2% at a 95% confidence level. (C) 2018 Published by Elsevier B.V.
- Viscosity measurements of poly(ethyleneglycol) 400 [PEG 400] at temperatures from 293 K to 348 K and at pressures up to 50 MPa using the vibrating wire techniquePublication . Sequeira, Maria C. M.; Pereira, Marta F. V.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando; Fareleira, JoãoThe article reports new measurements of the viscosity of Poly(ethyleneglycol) 400 [PEG 400] in the range (293-348) K and pressures up to 50 MPa. Complementary measurements of the density of the same sample of PEG 400 have been made covering the ranges of temperature and pressure, (293-353) K and (0.1-50) MPa, respectively. The viscosity measurements were performed using the vibrating wire technique in the forced mode of oscillation and the density measurements were carried out with an Anton Paar vibrating U-tube densimeter. The density raw data were corrected for viscosity effects. The overall uncertainty of the viscosity measurements is estimated to be less than +/- 2% for viscosities up to 68 mPa s and less than +/- 2.6% for higher viscosities. The densities have an estimated overall uncertainty of +/- 0.2%. The rheological behaviour of Poly(ethylene Glycol) 400 has also been studied, using a cone-plate Brookfield viscometer, in a temperature range between (293 and 333) K. The measurements were carried out at shear rates up to 20 s(-1) and shear stresses up to 2.20 Pa and have evidenced Newtonian behaviour. The viscosity data obtained were correlated by means of a modified hard-sphere based correlation technique. The relative root mean square, rms, deviation of the experimental results from the correlation equations is 0.54%, and their bias is practically zero. The density data obtained were correlated using a Tait-type equation. As a complement of the present study, the surface tension of PEG 400 was measured by the pendant drop method. This study aims to be useful for viscosity measurements using capillary viscometers. As far as the authors are aware, the present viscosity measurements are the first results to be published for PEG 400 at pressures higher than atmospheric pressure.
- In pursuit of a high-temperature, high-pressure, high-viscosity standard: the case of tris(2-ethylhexyl) trimellitatePublication . Wakeham, William A.; Assael, Marc; Avelino, Helena Maria Da Nóbrega Teixeira; Bair, Scott; Baled, Hseen O.; Bamgbade, Babatunde A.; Bazile, Jean-Patrick; Caetano, Fernando; Comunas, Maria J. P.; Daridon, Jean-Luc; Diogo, João C. F.; Enick, Robert M.; Fareleira, João; Fernandez, Josefa; Oliveria, M. Conceição; Santos, Tânica V. M.; Tsolakidou, Chrysi M.This paper presents a reference correlation for the-viscosity of tris(2-ethylhexyl) trimellitate designed to serve in industrial applications for the calibration of viscometers at elevated temperatures and pressures such as those encountered in the exploration of oil reservoirs and in lubrication. Tris(2-ethylhexyl) trimellitate has been examined with respect to the criteria necessary for an industrial standard reference material such as toxicity, thermal stability, and variability among manufactured lots. The viscosity correlation has been based upon all of the data collected in a multinational project and is supported by careful measurements and analysis of all the supporting thermophysical property data that are needed to apply the standard for calibration to a wide variety of viscometers. The standard reference viscosity data cover temperatures from 303 to 473 K, pressures from 0.1 to 200 MPa, and viscosities from approximately 1.6 to 755 mPa s. The uncertainty in the data provided is of the order of 3.2% at 95% confidence level, which is thought to be adequate for most industrial applications.
- Viscosity and density measurements on liquid n-tetradecane at moderately high pressuresPublication . Santos, Tânia V. M.; Pereira, Marta F. V.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando; Fareleira, JoãoThe main aim of the work is to study the viscosity and density of compressed normal tetradecane in the region of pressures from saturation to 10 MPa, where the available literature data are scarce. New measurements of the viscosity of n-tetradecane (n-C14) along eight isotherms in the range (283–358) K and at pressures up to 70 MPa, have been performed using the vibrating wire technique in the forced mode of operation. Density measurements have also been performed along nine isotherms in the temperature range from (283 to 373) K and pressures from (0.1 to 70) MPa. The vibrating wire viscosity results were correlated with density, using a modified hard-spheres scheme. The root mean square (rms) deviation of the data from the correlation is less than 0.32% and the maximum absolute relative deviation is less than 1.0%. The expanded uncertainty of the present viscosity data is estimated as ±1.5% at a 95% confidence level. 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. The isothermal compressibility and the isobaric thermal expansion were calculated by differentiation of the modified Tait equation. The uncertainties of isothermal compressibility and the isobaric thermal expansion are estimated to be less than ±1.7% and ±1.1%, respectively, at a 95% confidence level. The results are compared with the available literature data.
- Tris(2-Ethylhexyl) trimellitate (TOTM) a potential reference fluid for high viscosity. Part I: viscosity measurements at temperatures from (303 to 373)K and pressures up to 65MPa, using a novel vibrating-wire instrumentPublication . Diogo, João C. F.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando; Fareleira, JoãoNo literature data above atmospheric pressure could be found for the viscosity of TOTIVI. As a consequence, the present viscosity results could only be compared upon extrapolation of the vibrating wire data to 0.1 MPa. Independent viscosity measurements were performed, at atmospheric pressure, using an Ubbelohde capillary in order to compare with the vibrating wire results, extrapolated by means of the above mentioned correlation. The two data sets agree within +/- 1%, which is commensurate with the mutual uncertainty of the experimental methods. Comparisons of the literature data obtained at atmospheric pressure with the present extrapolated vibrating-wire viscosity measurements have shown an agreement within +/- 2% for temperatures up to 339 K and within +/- 3.3% for temperatures up to 368 K. (C) 2014 Elsevier B.V. All rights reserved.