A coupled computational fluid dynamics–dynamic mesh approach for predicting wax deposition in waxy natural gas throttling

Wax deposition during the throttling of waxy natural gas poses a critical challenge to the efficiency and safety of high-pressure transmission systems. This study develops a three-dimensional dynamic mesh deposition model, integrating nucleation, particle transport, and detachment mechanisms, to investigate the formation and evolution of wax deposits in throttle valves. Statistical analysis of nucleated particle sizes indicates that particle diameters predominantly range from 3 to 22 nm, with higher inlet pressures increasing the proportion of larger particles, while aperture ratio has a minor effect on size distribution but significantly affects the total number of precipitated particles. Deposition simulations reveal that wall deposition rates increase rapidly during the initial stage and gradually stabilize, with final rates ranging from 10% to 30%. The distribution and thickness of deposits are strongly influenced by the turbulent kinetic energy structure, with primary accumulation occurring near the throttle exit and downstream regions. Particle flow-following behavior and local flow disturbances collectively determine the spatial distribution and morphology of the deposit. These findings provide new insights into the coupled effects of pressure, aperture geometry, and turbulence on wax deposition and offer theoretical guidance for predicting and mitigating wax-related operational risks in high-pressure natural gas systems.