Study On Heat And Mass Transfer In Inner Layer Leakage Of Double Layer Oil Ipeline

The submarine oil pipeline plays a very important role in connecting the offshore oil well and the offshore oil and gas equipment.The submarine oil pipeline is more complex than the environment in which the buried pipeline is located.The economic losses caused by the leakage of the submarine oil pipeline are difficult to be estimated.The double layer oil pipeline is more stable,easy to maintain and widely used than single layer oil pipeline.Therefore,it is also very important to study the law of heat and mass transfer in the leakage medium of the submarine double layer oil pipeline.In this paper,the main research content of the double layer oil pipeline leakage is to study the law of heat and mass transfer after the leakage.The seepage of the leaky medium in the polyurethane thermal insulation materials belongs to the percolation of porous media.Firstly,the lattice Boltzmann method is used to study the seepage and heat and mass transfer of the leaky medium in a two-dimensional porous medium.A two-dimensional porous medium with different porosity and different particle sizes was constructed.The resistance coefficient of the flow of oil and water in the two-dimensional porous media was calculated.When the probability of growing nuclear distribution is the same,the connectivity of porous media becomes better with the increase of porosity.When the porosity is too small,the connectivity is poor.When the porosity is the same,with the increasing growth of nuclear distribution probability,the average particle size decreased in porous media.The three dimensional numerical simulation of the heat and mass transfer in the inner layer of a double layer oil pipeline was carried out by the calculated resistance coefficient of the porous medium.The effects of porosity,leakage time,leakage position and leakage speed on heat and mass transfer are analyzed.The results show that with the increase of porosity,pore fluid flow increase,accelerate the process of leakage out of reach outside the inner surface of the tube from the mouth leak after under the action of gravity flows down to the bottom of the pipe and effectively promote the conduction process,the double pipeline outer tube wall temperature increases quickly,high temperature and large area.When the porosity is small,the fluid seepage is slow,and the leakage medium will remain in the porous medium for a long time.The insulation layer will play a good role in thermal insulation and reduce the heat loss.The leakage position is different,which is influenced by gravity,and the flow path of the leakage medium is obviously different.With the increase of leakage speed,the leakage of the same porosity increases at the same time.When the leakage rate is small,the leakage of medium has not yet reached the above the outer tube wall inside began to flow downwards by gravity effect,little influence on the surface temperature of the outer tube.As the leakage rate increased,the leakage of medium can reach double pipeline leak leak just above the outer tube wall inside,and then under the influence of gravity downward flow.In this paper,the lattice Boltzmann method and Fluent software are used to study the heat and mass transfer law of the inner leakage of double layer oil pipeline.The method and research results can provide some references for future research on the leakage detection and maintenance of the seabed double deck oil pipeline.