Study On Heat-transfer Characteristics Of Crude Oil In Storage Tank Under Different Heating Modes

With the construction of a large number of crude oil tank in our country,the operation and management of oil tank have also suffered the severe challenge,especially the crude oil storage problem in cold areas in winter under low temperature environment.For winter low temperature environment in cold areas,if not heating the storage tank,crude oil in tank will happen solidification,and affect the safe operation of the storage tank seriously because of the surrounding ambient temperature below the freezing point of crude oil in tank.In order to avoid blind heating,it is need to research temperature change rules of crude oil in tank under the different heating mode,and then to provide theoretical guidance and support for practical production operation management.In this paper,the floating roof oil tank of some oil depot in Daqing area is choose as the research object,establishing the physical and mathematical model of the crude oil storage tank under the heating mode of tubular heating,loading and uploading oil and hot oil circulation,the numerical discretization method based on finite volume method is put forwad to simulate the floating roof tank heating process under the low temperature environment in winter.By simulating distributions of flow field and temperature field of crude oil in tank under the different heating mode,and to analyse oil flow and heat-transfer characteristics of crude oil tank,and evaluation indexs including heat energy utilization efficiency,heat dissipation power of storage tank,temperature rise rate and so on are put forwad to study on heat transfer of crude oil in storage tank under different heating modes.Through the analysis and research of tubular heating the following results are obtained,heating order of crude oil tank is that surrounding of heating tube,near the tank wall and tank roof as well as the tank center area;crude oil in tank form different levels of vortex flow which consists of different quantities,directions and sizes of the vortex;thermal boundary layer near the tank wall is 40 mm,and below the tank roof is 80 mm or 120 mm,and the boundary layer thickness is not changing with the heating process.And through the research of the way of loading and uploading oil the following results are obtained,loading and uploading oil process has the characteristics of the thermal buoyant jets,the cold oil which along the jet trajectory and near the position where jet collisions with tank top is heated priority,radial oil temperature changes uniformly and axial oil temperature presents hierarchical distribution.Through the research of the way of hot oil circulation heating the following results are obtained,oil near jet-flow trajectory and the top of tank is first heated,and then the tank wall and crude oil under the tank top are heated from top to bottom,at the last,the temperature of all the crude oil in tank tends to uniform.In the process of hot oil circulation heating,crude oil in tank near the tank wall which on the left of the jet-flow trajectory and the storage tank center area which on the right of jet-flow trajectory both form a low temperature areas and the size of them will change with the difference of the jet-flow velocity,jet-flow temperature and storage oil liquid level,and it will decrease until disappear as the progress of heating process.