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Measurements have been carried out for determining the viscosity of several nanofluids, in which different nanoparticles were dispersed in a base fluid of 60% propylene glycol (PG) and 40% water by mass. The nanoparticles were aluminum oxide (AFOj), copper oxide (CuO), silicon dioxide (SiC>2), titanium oxide (Ti02), and zinc oxide (ZnO) with different average particle diameters. Measurements were conducted for particle volume concentrations of up to 6% and over a temperature range of 243 K-363 K. All the nanofluids exhibited a Bingham plastic behavior at lower temperatures of 243 K-273 K and a Newtonian behavior in the temperature range of 273 K-363 K. Comparisons of the experimental data with several existing models show that they do not exhibit good agreement. Therefore, a new model has been developed for the viscosity of nanofluids as a function of temperature, particle volume concentration, particle diameter, the properties of nanoparticles, and those of the base fluid. Measurements were also conducted for single walled, bamboolike structured, and hollow structured multiwalled carbon nanotubes (MWCNT) dispersed in a base fluid of 20% PG and 80% water by mass. Measurements of these carbon nanotubes (CNT) nanofluids were conducted for a particle volume concentration of 0.229% and over a temperature range of 273 K-363 K, which exhibited a non-Newtonian behavior. The effect of ultrasonication time on the viscosity of CNT nanofluids was investigated. From the experimental data of CNT nanofluids, a new correlation was developed which relates the viscosity to temperature and the Peclet number. [ABSTRACT FROM AUTHOR]

In this study the pH levels of aluminum oxide (Al2O3), silicon dioxide (SiO2), and zinc oxide (ZnO) nanoparticles dispersed in propylene glycol and water mixture were measured in the temperature range of 0°C to 90°C. The volumetric concentration of nanoparticles in these fluids ranged from 0 to 10% for different nanofluids. The average particle sizes (APS) considered were from 10 nm to 70 nm. The pH measuring apparatus and the measurement procedure were validated by measuring the pH of a calibration fluid, whose properties are known accurately. The measured pH values agreed within less than ±0.5% with the published data reported by the manufacturer. Following the validation, the pH values of different nanofluids were measured. The measurements showed that pH of nanofluids decreased with an increase in temperature and increased with an increase in particle volumetric concentration. For the same nanofluid at a fixed volumetric concentration, the pH was found to be higher for larger particle sizes. From the experimental data, empirical models were developed for three nanofluids to express the pH as functions of temperature, volumetric concentration, and the size of the nanoparticles. [ABSTRACT FROM AUTHOR]

As part of a major project on studying the operational challenges in gas-to-liquids (GTL) transportation through the Trans Alaska Pipeline System (TAPS), the wax appearance temperatures (WAT) of GTL products and the Alaska North Slope Crude (ANSC) and their blends were measured. The WAT measurements of GTL products were based on the American Society for Testing and Materials (ASTM) D3117 standard, whereas the WAT measurements of ANSC and its blends with the GTL products were measured by the viscometry technique. The reliability of the viscometry technique was ascertained by comparing the WATs of the colorless GTL products measured by the ASTM D 3117 method. The WATs measured by the viscometry technique and the ASTM D3117 method were found to be in excellent agreement. [ABSTRACT FROM AUTHOR]

The feasibility of transporting gas-to-liquids (GTL) products (natural gas chemically converted to liquid hydrocarbons) through an existing oil pipeline—the Trans Alaska Pipeline System (TAPS)—for bringing value to Alaska's vast stranded natural gas resources is currently being investigated. As part of this major project, the phase behavior measurement and modeling of GTL and Alaska North Slope crude (ANSC) oil blends have been carried out. The saturation pressures for various types of GTL and ANSC oil blends were measured in a conventional windows based PVT apparatus. The phase behavior of GTL and ANSC oil blends were also modeled by the Peng-Robinson and Soave-Redlich-Kwong equations-of-state. The measured and modeled saturation pressures were found to be in close agreement. The results also indicated that the GTL and ANSC oil blends would always exist as single-phase liquid under the current TAPS operating conditions. [ABSTRACT FROM AUTHOR]

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations. [ABSTRACT FROM AUTHOR]

As part of a major project on studying the transportation of gas-to-liquids (GTL) through the existing Trans Alaska Pipeline System (TAPS), the density and viscosity of GTL and the Alaskan North Slope Crude (ANSC) and their blends were measured. All density and viscosity measurements were performed, using the Anton–Paar vibrating tube densitometer and a cone and plate viscometer respectively, at temperatures ranging from 20 oC to 60 °C at atmospheric pressure. The accuracy of the measured data has been ascertained. In addition to the density and viscosity data, other data reported for GTL and ANSC include compositions. Finally, generalized dens ty and viscosity correlations for the measured data are presented. [ABSTRACT FROM AUTHOR]

As part of a project on studying the transportation of gas-to-liquids (GTL) through the Trans Alaska Pipeline System (TAPS), two GTL transportation modes are evaluated: (i) as single slugs (batches) and (ii) commingled (mixed) with the Alaskan North Slope Crude (ANSC) oil. The pertinent energy equations are solved for both the batch and commingled flow modes. The solutions of these equations are analytically presented for determining among other parameters, the pressure gradient and the slug length required for batching. A comparison of the pressure gradient calculations is presented for the batching and the commingled flow cases. [ABSTRACT FROM AUTHOR]

A nanofluid is the dispersion of metallic solid particles of nanometer size in a base fluid such as water or ethylene glycol. The presence of these nanoparticles affects the physical properties of a nanofluid via various factors including shear stress, particle loading, and temperature. In this paper the rheological behavior of copper oxide (CuO) nanoparticles of 29 nm average diameter dispersed in deionized (DI) water is investigated over a range of volumetric solids concentrations of 5 to 15% and various temperatures varying from 278-323 degrees K. These experiments showed that these nanofluids exhibited time-independent pseudoplastic and shear-thinning behavior. The suspension viscosities of nanofluids decrease exponentially with respect to the shear rate. Suspension viscosity follows the correlation in the form ln(mus) = A(1/T)-B, where constants A and B are the functions of volumetric concentrations. The calculated viscosities from the developed correlations and experimental values were found to be within +/- 10% of their values.