Analysis of leaked LNG flow and consequent thermal effect for safety in LNG cargo containment system

As the large liquefied natural gas (LNG) carrier has emerged as an important LNG transportation, rigorous safety analysis of the carrier is required to achieve reliable technological solutions for safely transporting LNG. The present study uses numerical simulation (conjugate thermal analysis) to investigate LNG leakage and the consequent temperature change of the hull׳s steel plate in a LNG cargo containment system (CCS). To validate the numerical approach used in the study, experimental investigation on the temperature behavior of the hull׳s plate was conducted. The experimentally determined ductile-to-brittle transition temperature (DBTT) was used as the index of critical temperature for the hull׳s plate. A numerical simulation was used to estimate the behavior of cryogenic liquid in a porous structure in an LNG CCS and the resulting temperature change of the hull׳s plate due to LNG leakage under any filling conditions (various inlet pressures of leaking LNG and defect sizes). According to the numerical study, the thermal safety of the hull׳s plate is guaranteed in case where the LNG leakage hole is 2 mm in diameter. The critical leakage hole size where temperature of hull׳s plate did not reach a DBTT lies between 2 mm and 5 mm under the leakage conditions.