Jing Li

Ocean Thermal Energy Conversion (OTEC) is characterized by its abundant reserves and pollution-free nature, enabling stable power generation around the clock. Since the power output of an OTEC system is significantly influenced by the energy available from cold and warm seawater, the accurate evaluation of the outlet temperature of the cold-water pipe (CWP) is crucial. To analyze the heat transfer performance of the CWP, this paper investigates the temperature field of the OTEC CWP and employs numerical simulation methods to conduct finite element analysis of the temperature field under different discharge conditions. The results indicate that during the pumping of deep-sea cold water through the CWP, heat is absorbed from the warmer upper seawater layers. When the pumping discharge rate is higher, the shorter fluid residence time due to higher flow velocity results in a lower outlet temperature. Compared to steel CWPs, high-density polyethylene (HDPE) is more suitable for OTEC systems due to its lower thermal conductivity and density.

Subsea wellhead systems are the crucial equipment for the development of oil and gas resources offshore, while the sealing device plays a vital role as the main component of the wellhead system. Once the seal fails, it is necessary to retrieve the original wellhead system and either repair the sealing device or reinstall a new one. This will result in a delay in normal production and an increase in development costs. Therefore, a novel subsea wellhead sealing device is designed. A finite element analysis model is developed to study the underwater wellhead sealing mechanism regarding the equivalent stress and contact stress. The research results show that as the driving block gradually increases from 4 mm to 12 mm, the stress of the 12 convex parts on the sealing body also increases. The maximum equivalent stress reaches 3.5 times the yield limit, indicating that it has entered the yield stage and can achieve a more effective seal. The analysis of the contact stress of the sealing body reveals that the contact stress of the driving block increases, leading to plastic deformation of the sealing body while driving it to achieve a complete seal. In general, the finite element simulation results are consistent with the engineering practice. By analyzing the sealing characteristics, it can serve as the foundation for designing and providing theoretical support for the optimization of the metal-sealing structure.