Dynamic Viscosity of Methane Hydrate Systems from Non-Einsteinian, Plasma-Functionalized Carbon Nanotube Nanofluids

TL;DR

This study measures the viscosity of oxygen-functionalized carbon nanotube nanofluids under various conditions, revealing their effects on viscosity behavior, hydrate formation, and potential implications for flow and hydrate management.

Contribution

It introduces the effects of plasma-functionalized carbon nanotubes on methane hydrate systems, highlighting their influence on viscosity and hydrate formation dynamics.

Findings

O-MWCNTs reduce effective viscosity and add weak pressure dependence.

O-MWCNTs accelerate hydrate formation times.

Presence of O-MWCNTs limits hydrate formation conditions.

Abstract

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.