Abstract:

An analysis model is established to study the heat leakage process in a liquid cargo tank, enabling the calculation of the temperature field distribution of the membrane-type cargo under various working conditions. Based on the calculated temperature field distribution data, the heat leakage and pressure holding time are analyzed. The influence of ambient temperature, filling rate, and cabin pressure on the temperature field distribution and the variation of holding time are discussed. The results indicate that when the ambient air temperature rises from 20℃ to 45℃, the heat leakage of the cargo tank increases by 4.17 kW, while the holding time decreases by 11.1 h. The ambient air temperature primarily affects the temperature distribution in the cabin above the water level. As the filling rate increases from 50% to 98%, the reduction in gas phase space enhances the solid-liquid heat transfer area of the bulkhead, leading to an overall heat leakage increase of 85.2 W in the liquid cargo tank, and the holding time extends by 121.2 h. There exists an optimal loading rate for achieving the longest holding time, with the maximum holding time of 317.8 h occurring at a loading rate of 95%. When the cabin pressure increases by 20 kPa above atmospheric pressure, the temperature gradient between the interior and exterior of the cargo decreases, resulting in a heat leakage reduction of approximately 1.09 kW.

Key words: natural gas, membrane LNG carrier, temperature distribution, boil off rate, heat transfer, convection

摘要：

基于液货舱漏热过程的特点，建立分析模型，计算薄膜型液货舱的温度场分布，通过分析漏热量的时效影响得出保压时间的变化，验证了模型的可行性，并探讨了环境温度、装载率、舱内压力等因素的影响。结果表明：当环境空气温度从20℃升至45℃时，液货舱漏热量增加4.17 kW，保压时间减少11.1 h，环境空气温度主要影响水位线以上舱室的温度分布；当液货装载率从50%提升至98%时，气相空间减少导致舱壁固液换热面积增大，液货舱整体漏热量增加85.2 W，保压时间延长121.2 h；随着装载率的上升，存在最佳装载率使保压时间达到最长，最佳装载率为95%，最大保压时间为317.8 h；当舱内压力从大气压升高20 kPa时，液货舱内外温度梯度下降，漏热量减少约1.09 kW。

关键词: 天然气, 薄膜型LNG船, 温度分布, 蒸发率, 传热, 对流