In this study, thermal-fluid-solid coupled simulations on the gas-phase pre-cooling operation of the corrugated cryogenic hoses were performed. Attention was focused on the temporal evolution and spatial distribution of transient thermal stress in the hose structure caused by convective heat transfer of the cooling medium, Liquefied Natural Gas Boil-Off Gas (BOG). The effects of different corrugated hose parameters, i.e., boundary conditions, hose lengths, BOG inlet flow rates, and corrugation shapes (C-type and U-type), on the transient thermal stress behavior were thoroughly assessed. The thermal stress developed at different locations of the corrugated hoses with these parameters is found to be governed by two major factors: the boundary constraint and local temperature gradient. The objective of this study is to offer practical insights for the structural strength design of corrugated cryogenic hoses and effective pre-cooling strategies, aiming to mitigate structural safety risks caused by excessive thermal stress.

The exploration and development of natural gas resources in deep-sea regions present both significant opportunities and challenges. These resources, predominantly composed of methane, offer a substantial and relatively untapped energy potential. For deep-sea natural gas development, the collected gas is first transported to a nearby floating liquefied natural gas (LNG) production storage and offloading unit (FLNG) before received by a LNG carrier for transportation back to land (Won et al., 2014). Traditionally, LNG transport between the FLNG and the LNG carrier is achieved by rigid discharge arms, which requires side-by-side alignment of the two vessels with minimal relative motion (Eide et al., 2011). However, under harsh environmental conditions, this requirement is quite difficult to satisfy with the current mooring technology. As an alternative to the rigid discharge arms, corrugated cryogenic hoses (as shown in Fig.1) has been developed to tackle this problem. With insulation to prevent pipeline leakage and vaporization and the ability to float in the water, it allows for a distance of up to 100 meters between the FLNG and LNG carriers, thus enhancing operational safety in harsh offshore conditions. In recent years, corrugated cryogenic hoses have been increasingly used in offshore LNG production and transportation. Most of the relevant studies focused on the overall design (Yang et al., 2017), structural strength analysis (Yan et al., 2022), and flow and heat transfer characteristics of the internal flow (Yang et al., 2022). The safety issues that may be encountered in the practical field application of the cryogenic hose are not fully understood.