Simulation and analysis on precooling process of membrane LNG carriers

doi:10.11949/0438-1157.20241389

Abstract

Abstract:

Precooling the LNG carrier prior to loading is a critical process to ensure the reliability of cargo equipment and enclosure structures. This study investigates membrane LNG carriers by constructing a two-dimensional cylindrical mesh using similar methodologies, simulating both the flow distribution within the tank and the enclosure temperature. The calculations not only demonstrate efficient performance but also accurately capture the variations in the temperature gradient. The results highlight the importance of monitoring temperature changes at the center and corners of the bottom. To ensure that the main enclosures cool at a safe gradient, an operational strategy regarding the rate of liquid supply should be carefully considered.

Key words: LNG carrier, membrane carrier, precooling process, numerical simulation

摘要：

在LNG船的装载过程中，预冷作为确保舱内设备和围护结构可靠性的关键工艺环节，具有重要作用。以LNG船薄膜型液货舱为研究对象，通过构建二维柱坐标系网格，并采用相似方法对液货舱内流场及壁面温度进行数值模拟。该研究不仅显著提升了计算效率，同时较好地还原了液货舱在预冷过程中温度梯度的演变过程。研究结果表明，应重点关注液货舱舱底中心区域以及舱底与侧面交界处的温度变化；为确保主屏蔽层温度下降梯度处于安全范围内，预冷流量需在特定控制策略下进行精准调节。

关键词: LNG船, 薄膜舱, 预冷过程, 数值模拟

CLC Number:

U 674.13⁺3.3

Hao HUANG, Wen WANG, Longkun HE. Simulation and analysis on precooling process of membrane LNG carriers[J]. CIESC Journal, 2025, 76(S1): 187-194.

黄灏, 王文, 贺隆坤. LNG船薄膜型液货舱预冷过程模拟与分析[J]. 化工学报, 2025, 76(S1): 187-194.

Figures/Tables 16

Fig.1 Structure of a membrane type carrier[1-3]

Fig.2 Structure of a membrane type carrier (a)[2] and its simplified cylindrical model (b)

Table 1 Parameters of a membrane type carrier and its simplified cylindrical model

参数	原始模型	二维柱坐标系
总舱容/m³	41096	41096
底面面积/m²	1310	1483
顶面面积/m²	1048	1483
侧面面积(含斜面)/m²	5107	3783
总换热面积/m²	7465	6749

Fig.3 Boundaries of the fluid domain

Table 2 Parameters of the boundary condition

边界类型	参数类型	参数取值
进口边界	进口速度/(m·s^-1)	0.3325
	进口区域/m	0 ≤ r ≤ 2.77625
	进口温度/K	120
	折算流量/(kg·h^-1)	6400
出口边界	出口压力/kPa	125
冷源项影响区域	冷却功率/(W·m^-3)	542

Table 3 Structure and properties of the enclosures［16-18］

结构	厚度/mm	材料	比定压热容/(J·(kg·K)^-1)	密度/(kg·m^-3)	热导率/(W·(m·K)^-1)
主屏蔽层	0.7	殷瓦钢	480	8130	13.80
主绝缘层	230	膨胀珍珠岩	387	50	0.03
次绝缘层	300	膨胀珍珠岩	387	50	0.03
船舱内壳	30	船用钢	480	8130	13.80

Fig.4 Mesh of the model

Fig.5 Nodes of the enclosures

Fig.6 The average temperature of the main insulation layer varies with the precooling time

Fig.7 Temperature distribution after 1 h of precooling

Fig.8 Radial velocity distribution after 1 h of precooling

Fig.9 Axial velocity distribution after 1 h of precooling

Fig.10 Measuring points on the primary barrier

Fig.11 Temperature distribution of the primary barrier after 1000 s of precooling

Fig.12 Temperature curve of the primary barrier under different liquid supply rates

Fig.13 Descending gradient of temperature curve of the primary barrier under different liquid supply rates

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