Transport of liquefied natural gas (LNG) by ship occurs globally on a massive scale. The large temperature difference between LNG and water means LNG will boil violently if spilled onto water. This may cause a physical explosion known as rapid phase transition (RPT). Since RPT results from a complex interplay between physical phenomena on several scales, the risk of its occurrence is difficult to estimate. In this work, we present a combined fluid-dynamic and thermodynamic model to predict the onset of delayed RPT. On the basis of the full coupled model, we derive analytical solutions for the location and time of delayed RPT in an axisymmetric steady-state spill of LNG onto water. These equations are shown to be accurate when compared to simulation results for a range of relevant parameters. The relative discrepancy between the analytic solutions and predictions from the full coupled model is within for the RPT position and within $2\text{\%}$ for the time of RPT. This provides a simple procedure to quantify the risk of occurrence for delayed RPT for LNG on water. Due to its modular formulation, the full coupled model can straightforwardly be extended to study RPT in other systems.

船上液化天然气（LNG）的运输在全球范围内是大规模的。LNG与水之间的温差很大，这意味着LNG溅到水上会剧烈沸腾。这可能会导致物理爆炸，称为快速相变（RPT）。由于RPT是由几个尺度上的物理现象之间的复杂相互作用导致的，因此难以估计其发生的风险。在这项工作中，我们提出了流体动力学和热力学的组合模型来预测RPT延迟发作。在完全耦合模型的基础上，我们推导出了液化天然气向轴对称稳态泄漏时延迟RPT的位置和时间的解析解。与一系列相关参数的仿真结果相比，这些方程式被证明是准确的。$2\text{％}$在RPT期间。这提供了一个简单的程序来量化水上液化天然气延迟RPT发生的风险。由于其模块化的表述，全耦合模型可以直接扩展为研究其他系统中的RPT。