氮气预冷LNG管道温度变化规律算法研究

Research on temperature variation algorithm in nitrogen pre-cooling LNG pipeline

为研究氮气预冷LNG卸料管道过程中的管道顶、底温度变化规律,并对管道预冷过程中的顶、底温度变化进行预测计算,利用Fluent软件,建立带π型膨胀弯的LNG管道三维模型,模拟氮气预冷LNG管道过程的温度变化。建立了一维氮气预冷管道计算模型,通过时间与空间的离散化、时间与空间的迭代计算进行模型求解。通过分析LNG管道预冷过程中顶底温差影响因素,推导管道顶底温度理论计算经验关联式,将氮气预冷LNG管道数值模拟结果用于理论计算经验关联式拟合。利用数值模拟结果对经验关联式进行验证,结果表明在拟合数据的样本空间内,利用经验关联式计算管道预冷过程中的顶、底温度误差在10%以内。

In order to investigate the thermal behavior at the top and bottom sections of an LNG unloading pipeline during a nitrogen pre-cooling process,and to computationally predict these temperature variations,Fluent software was utilized to construct a three-dimensional model of an LNG pipeline withπ-type expansion bend.The model was employed to simulate the temperature dynamics throughout the nitrogen pre-cooling phase of the LNG pipeline.A one-dimensional computational model for the nitrogen pre-cooling pipeline was developed,incorporated spatial and temporal discretization alongside iterative calculations for temporal and spatial domains.The analysis of factors influencing the thermal gradient between the top and bottom sections during the pipe-line’s pre-cooling phase led to the derivation of an empirical correlation formula for theoretical temperature calculations.The numerical simulation results of the nitrogen pre-cooling LNG pipeline were applied to fit this theoretical empirical correlation.Subsequent validation of this empirical correlation with numerical simulation data demonstrated that,within the confines of the fitted data’s sample space,the predictive error for the top and bottom temperatures during the pre-cooling process remains within 10%accuracy.