| description abstract | Abstract. With the increasing penetration of renewable energy in oilfield power systems, fluctuations in operating temperature render pipeline operation below the critical wall sticking temperature (CWST) increasingly unavoidable. However, the coupled evolution of oil adhesion and removal under continuous flow conditions remains poorly understood. In this study, the competitive mechanism of condensed oil adhesion and removal in cold transportation pipelines is systematically investigated. Experimental results show that temperature reduction induces the evolution of wax crystals from dispersed precipitates into an interconnected three-dimensional network, significantly enhancing the structural integrity of the condensed oil. Concurrently, temperature-dependent variations in surface-energy (SFE) components intensify interparticle cohesive interactions. As a result, the system transitions into a cohesion-dominated regime, in which hydrodynamic shear is insufficient to overcome the cohesive energy barrier. This transition results in rapid thickening of the adhered oil layer and a pronounced reduction in effective flow area. During the removal process, temperature elevation disrupts the wax crystal network and weakens interparticle cohesive interaction, triggering a transition toward the hydrodynamic shear-controlled detachment regime. Furthermore, based on the torque balance, the critical speed for the transition of the dominant mechanism of the cold pipeline is determined, and the predicted average relative error is less than 25%. | |
