Viscosity evolution of water glycol in deep-sea environment at high pressure and low temperature

Abstract

Using water glycol as a working medium is an important development direction for deep sea hydraulic drives, its viscosity is an important parameter for hydrodynamic lubrication and seriously influenced by the deep-sea environment. In this paper, Non-Equilibrium Molecular Dynamics method was used to predict the viscosity of water glycol with 0%, 25%, 50%, 75% and 100% water content in the deep-sea environment based on the OPLS-AA force field. The simulation results have an error of less than 10% compared to available experimental data. Detailed analysis of hydrogen bonding and water molecular structure is provided to explain why the viscosity of water decreases with increasing sea depth from 2000 m to 11,000 m. A fitted equation is proposed to calculate the viscosity of water glycol by analyzing the effect of temperature, pressure, and water content on the viscosity of water glycol in deep-sea environment.