Ra数对停输管道中心点原油温度影响研究

Study on the Influence of Ra Number on the Temperature of Crude Oil at the Center Point of Shutdown Pipeline

热油管道停输后,不均匀的温度场会使原油产生自然对流,Ra数是描述自然对流传热强弱的无量纲量,分析Ra数对管道中心点原油温度的影响,对确定管道安全允许停输时间有着重要的意义。考虑了原油的自然对流,采用分区法建立了基于焓法的格子Boltzmann双分布函数模型,编程计算分析了Ra数对热油管道截面温度场与管道中心点温度的影响。结果表明:随着Ra数的增大,增强的自然对流会扰动原油温度场,从而扰动管道中心点原油温度,使得原油换热第一、二阶段的管道中心点温降速率显著加快,温降曲线由线性下降过渡为非线性下降,表现出对流换热的特性,而原油换热第三阶段的温降速率受Ra数影响较小。

After the shutdown of hot oil pipeline,the uneven temperature field will cause natural convection of crude oil.Ra number is a dimensionless quantity describing the strength of natural convection heat transfer.It is very important to analyze the influence of Ra number on the crude oil temperature at the center of the pipeline,which is of great significance to determine the allowable shutdown time of the pipeline.In this paper,considering the natural convection of crude oil,a lattice Boltzmann double distribution function model based on enthalpy method was established by using partition method.The influences of Ra number on the temperature field of hot oil pipeline section and the temperature of pipeline center point were analyzed by programming.The results showed that,with the increase of Ra number,the enhanced natural convection disturbed the temperature field of crude oil,thus disturbing the crude oil temperature at the central point of the pipeline.The temperature drop rate of the first and second stages of crude oil heat transfer was significantly accelerated,and the temperature drop curve changed from linear decline to nonlinear decline,showing the characteristics of convective heat transfer,while the temperature drop rate of crude oil in the third stage of heat transfer was less affected by Ra number.