Investigation of thermal behavior of long-distance multilayer pipeline with MicroPCM particles

Abstract

Long-distance transport of oil and gas in the harsh subsea environment needs reliable pipeline thermal management to prevent wax deposition and hydrate formation. Multilayer pipeline with the PCM-matrix composite material, made of microencapsulated phase change material particles (MicroPCM particles) and polymer matrix material, is proposed as an effective method to meet the flow assurance challenges owing to its thermal energy storage. Compared with the direct applications of PCM, the PCM-matrix composite material can avoid the possible leakage of its liquid phase and decrease the installation difficulty. Theoretical studies are carried out to investigate the proposed multilayer insulation system in a long horizontal pipeline, which embeds an intermediate insulation layer made of the PCM-matrix composite layer. Considering the storage or release of the latent heat and the changes of thermal properties during the phase change process, the global characteristics of the PCM-matrix composite layer is calculated based on the porous media theory. A pseudo-3D model coupled to the finite difference numerical method is developed to simulate the start-up and shut-in transient processes. To address the liquid and solid states of PCM and their interface, the model for the PCM-matrix composite layer is constituted in the form of enthalpy conservation. The influence of the thermal properties of different matrix and PCM materials on the cooldown time is examined. By analyzing the temperature distributions of produced fluid during start-up and shut-in, the current study shows that the use of MicroPCM particles in the composite layer can prolong the maximum cooldown time. In addition, the geometrical parameters, such as the volume fraction of MicroPCM particle and the thickness of the composite layer, are found to also play a role in affecting the extent of the prolongation of the cooldown time.