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- Viscosity and density measurements on liquid n-heptadecane at high pressuresPublication . Sequeira, Maria Carolina; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, JoãoThis article reports novel measurements of the viscosity, eta, 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(eta) = 0.015.eta with a confidence level of 0.95. Complementary measurements of the density, rho, 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(rho) = 0.002.rho 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.
- Density and rheology of tris(2-ethylhexyl) trimellitate (TOTM)Publication . Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando; Diogo, João C. F.; Fareleira, João; Pereira, Marta F. V.; Santos, Fernando J V; Santos, Tânia V. M.; Wakeham, William A.This article presents new density data and some rheological studies on tris(2-ethylhexyl) trimellitate (TOTM) which has recently been proposed as a reference fluid for viscosity at high temperatures and high pressures. The density data have been obtained with the aid of an Anton Paar DMA HP U-tube instrument, covering temperatures from 328 to 423 K and pressures up to 70 MPa, and they are aimed at extending the temperature range of previous results. They are also used to check the effect of interlot consistency of the density data for TOTM. The presente density measurements are compared with previously published data. Rheological tests were carried out to complement earlier studies. Particular attention is given to the shear rate range of greatest interest for the proposed use of TOTM as an industrial reference fluid for viscosity: the tests include shear stresses up to 750 Pa and shear rates up to 4000 s−1 under atmospheric pressure. The tests were carried out using a Parallel Plate Rheometer AR1500ex10C4298. The results at a temperature of 298 K corroborate the previous findings that TOTM is Newtonian below a shear rate of 600 s−1, which is entirely compatible with its use as an industrial calibrating fluid for viscosity. At shear rates higher than 600 s−1 a shear-thinning like behavior is observed.
- 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.
- Density measurements of compressed dipropyl, dibutul, bis (2-ethylhexyl) adipates from (293 to 373K) at pressures up to about 68MPaPublication . Diogo, João C. F.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, JoãoThe article reports density measurements of dipropyl (DPA), dibutyl (DBA) and bis(2-ethylhexyl) (DEHA) adipates, using a vibrating U-tube densimeter, model DMA HP, from Anton Paar GmbH. The measurements were performed in the temperature range (293 to 373) K and at pressures up to about 68 MPa, except for DPA for which the upper limits were 363 K and 65 MPa, respectively. The density data for each liquid was correlated with the temperature and pressure using a modified Tait equation. The expanded uncertainty of the present density results is estimated as 0.2% at a 95% confidence level. No literature density data at pressures higher than 0.1 MPa could be found. DEHA literature data at atmospheric pressure agree with the correlation of the present measurements, in the corresponding temperature range, within +/- 0.11%. The isothermal compressibility and the isobaric thermal expansion were calculated by differentiation of the modified Tait correlation equation. These two parameters were also calculated for dimethyl adipate (DMA), from density data reported in a previous work. 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. Literature data of isothermal compressibility and isobaric thermal expansivity for DMA have an agreement within +/- 1% and +/- 2.4%, respectively, with results calculated in this work. (C) 2014 Elsevier B.V. All rights reserved.