Applied Research On The Electric Heat Tracing System Of Nature Gas Pipelines

Compared with the atmospheric environment,soil environment is the important environmental conditions in pipeline transport and the process of tanks storage.Because of the complexity of the soil physical and chemical properties,the heat transfer characteristics of the soil are more difficult to predict.Accurate soil temperature field analysis is the basis of the study of hydraulic and heating change rule of the oil pipeline,optimization and adjustment of pipeline operation scheme and the calculation and analysis of the Crude oil temperature field in storage tanks.In view of the limitations of conventional methods of the soil temperature field analysis,this paper uses the method which combines the field test with the numerical simulation,we have independently designed and developed a set of soil temperature field test device.This device can conform to the safety of the field test of fire and explosion requirements.It can also achieve continuous testing,read and storage work of different depth and the same depth but different level position's soil temperature.In the aspect of theory analysis,the heat transfer process of the soil temperature field is simplified and we have established the relevant physical and mathematical model.We adopt the regional discretization method and on the basis of the finite volume method to solve the heat transfer equation.Analysis of the soil temperature field in the different conditions shows that the temperature field of the soil under natural condition is mainly affected by the environment temperature.And the influence decreases with increased depth.Compared with the environment temperature,the change of the soil temperature under natural condition has hysteresis phenomenon,and the hysteresis effect increases with increased depth.Influenced by the storage tank,the soil temperature field will vary;the lower the environment temperature is,the more significant the effect is.The isotherms are divided into two parts.Some are around the bottom of the tank,forming a cluster of approximate elliptical isotherms,whose value nearer to the around the bottom is higher.The others are forming isotherms around the boundary of the soil surface.With the increasing of the environment temperature,the effect caused by the storage tank is weakening,the soil isotherms transfer to a group of parallel lines.The larger the tank's capacity is and the higher the oil temperature is,the more obvious the effect to the soil temperature around is.By contrasting the numerical simulation results and the field test results of the soil temperature field,in general,the both relative deviations are less than 10%according to the date.And the deviation of the shallow soil measuring point is larger,with the increase of the soil depth,the deviation decreases.Compared with the natural soil temperature field,the deviation is larger when there is a storage tank.