Modeling approach for discharge rate from liquefied natural gas carrier

The LNG (liquefied natural gas) carriers accidental release will result in disastrous safety and environmental concerns. The modeling approach of discharge rates is important for hazard predictions of LNG carrier accidental releases. The commonly-used methods always assumed that LNG tank was rectangle and head-space pressure was constant, while this was not very agreed with the realistic. In this paper, the interaction mechanism of LNG evaporating rate, vacuum relief valves make- up rate, discharge rate and headspace pressure change was studied, then the influence of tank types on discharge rate was analyzed, at last an improved modeling approach of discharge rate from a punctured LNG carrier was developed. The calculating results of various modeling approaches indicate: compared with other discharge rate models, the improved modeling approach developed in this paper can not only account for the influence of the decreasing hydrostatic pressure head above the hole on discharge rate of LNG, but also account for the low headspace pressure in the LNG tank reducing the rate of outflow. Meantime, the improved modeling approach can also reflect the influence of cargo tank designs on discharge rate of LNG.