Browsing by Author "Wakeham, William A."
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- 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.
- 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.
- Tris(2-ethylhexyl) trimellitate (TOTM) as a potential industrial reference fluid for viscosity at high temperatures and high pressures: New viscosity, density and surface tension measurementsPublication . Diogo, João C. F.; Avelino, Helena Maria Da Nóbrega Teixeira; Caetano, Fernando J. P.; Fareleira, Joao M. N. A.; Wakeham, William A.Tris(2-ethylhexyl) trimellitate (TOTM) was recently suggested as a reference fluid for industrial use associated with high viscosity at elevated temperature and pressure. Viscosity and density data have already been published on one sample covering the temperature range (303-373) K and at pressures up to about 65 MPa. The viscosity covered a range from about (9 to 460) mPa s. In the present article we study several other characteristics of TOTM that must be available if it were to be adopted as a standard. First, we present values for the viscosity and density obtained with a different sample of TOTM to examine the important feature of consistency among different samples. Vibrating-wire viscosity measurements were performed at pressures from (5 to 100) MPa, along 6 isotherms between (303 and 373) K. Density measurements were carried out from (293 to 373) K up to 68 MPa, along 4 isotherms, using an Anton Paar DMA HP vibrating U-tube densimeter. Secondly, we report a study of the effect of water contamination on the viscosity of TOTM, performed using an Ubbelhode viscometer under atmospheric pressure. Finally, in order to support the use of TOTM as a reference liquid for the calibration of capillary viscometers, values of its surface tension, obtained by the pendant drop method, are provided. (C) 2016 Elsevier B.V. All rights reserved.