High-pressure rheology of alumina-silicone oil nanofluids

Dynamic viscosity of methane hydrate systems from non-Einsteinian, plasma-functionalized carbon nanotube nanofluids

The viscosity of oxygen-functionalized multi-walled carbon nanotube (O-MWCNT) nanofluids was measured for concentrations from 0.1 to 10 ppm under conditions of 0 to 30 MPag pressures and 0 to 10 °C temperatures. The presence of O-MWCNTs did not affect the temperature dependence of viscosity but did reduce the effective viscosity of solution due to cumulative hydrogen bond-disrupting surface effects, which overcame internal drag forces. O-MWCNTs added a weak pressure dependence to the viscosity of solution because of their ability to align more with the flow direction as pressure increased. In the liquid to hydrate phase transition, the times to reach the maximum viscosity were faster in O-MWCNT systems compared to the pure water baseline. However, the presence of O-MWCNTs limited the conditions at which hydrates formed as increased nanoparticle collisions in those systems inhibited the formation of critical clusters of hydrate nuclei. The times to viscosity values most relevant to technological applications were minimally 28.02% (200 mPa s) and 21.08% (500 mPa s) slower than the baseline, both in the 1 ppm system, even though all systems were faster to the final viscosity. This was attributed to O-MWCNT entanglement, which resulted in a hydrate slurry occurring at lower viscosity values.

Advances and challenges in the high-pressure rheology of complex fluids

Complex fluids and soft materials are ubiquitous in nature and industry. In industrial processes, these materials often get exposed to high hydrostatic pressures. Some examples include polymer melts, crude oils, gas hydrates, food systems, foams, motor oils, lubricants, etc. In spite of the relevance and utilization of hydrostatic pressure in many industrial applications, the role of pressure on the rheological properties has not been examined extensively in the literature. We review the high-pressure rheometric systems and present advantages and drawbacks of various kinds of rheometers such as capillary rheometer, sliding plate rheometer, falling ball viscometer, and rotational rheometer. By outlining the design complexities, precision, low-torque resolution limits and the inherent error sources of each type are critically evaluated. Furthermore, the high-pressure rheology data, chosen to cover a broad range of pressures and material class ranging from simple Newtonian fluids (incompressible), complex non-Newtonian fluids and compressible fluids featuring various key applications from different industries, are reviewed. The literature suggests, while effect of pressure on the rheological behavior is vital for many applications, compared to the effects of temperature on the rheological behavior, knowledge of the effect of pressure is still in its infancy.

Viscosity measurement dataset for a water-based drilling mud-carbon nanotube suspension at high-pressure and high-temperature

This data article presents the measured viscosity of a carbon nanotube (CNT) suspension in water-based drilling mud, also termed as nano-muds (“Rheology of a colloidal suspension of carbon nanotube particles in a water-based drilling fluid” Anoop et al., 2019). The apparent viscosity values of the nano-mud samples are measured using a high-pressure high-temperature viscometer at different shear rates, working based on a rotor and bob technique. The pressure and temperature of the samples are independently varied during the measurements from ambient conditions to 171 MPa and 176 °C, respectively, within two experimental schedules. Viscosity measurements for varying nanoparticle concentration, shear rate, pressure, and temperature are reported here for different CNT concentrations.