Research On Temperature Field Distribution Of Long-Stay Oil In Large Storage Tank

Crude oil depot is the coordination link of oil production,process and transportation.Oil metering of crude oil storage tank in our country mainly relies on manual measurement,with shortcomings of many uncertain factors and strong randomness.In recent years,with the rapid development of computer system,the researchers begin to solve the storage measurement problem with simulation technology.However,most present simulation methods couldn't take the effect of oil temperature change into account,making a certain deviation between tank capacity table and real metering result.Calculation of tank capacity table needs the average tank wall temperature,which has many algorithms because of the uncertainty of oil temperature distribution.And oil temperature change leads to the variant floating roof submerged volume,while the current calculation volume is treated as a fixed value.The above two reasons cause measurement errors,and bring about trade disputes.In this paper,using of numerical simulation,laboratory experiment and field test,the temperature field distribution of long-stay oil in large storage tank was studied.The main research content is as follows:Firstly,according to the similarity principle,the mathematical model of asimulation tank was designed,and the different heating and cooling conditions were simulated;then,a simulation tank indoor experimental system in equal proportion was built,and the correctness of simulation result is verified by experiment.Next,the mathematical simulation model of a real large oil tank was also built,and through the simulation,we could find that the oil temperature field distribution is divided into two stages due to the air temperature changes: the overall cooling stage when oil temperature is higher than air temperature,and the layered heating stage when oil temperature is lower than air temperature.When oil temperature is higher than air temperature,the natural convection of crude oil is enhanced,the heat transfer rate is high,and so the oil temperature is basically the same.When oil temperature is lower than air temperature,the natural convection of crude oil is inhibited,the heat transfer rate is low,and so the oil temperature is layered.The field tests of a large storage tank in extreme weather conditions were carried out.Contrasting the field test result with simulation result,they were consistent,which verified the simulation.The test results shows that there is no temperature difference in the horizontal direction in the storage tank;the thick oil condensate reservoir at tank bottom influences the oil temperature field distribution within 2.5m to the bottom plate;the oil area is divided into bottom conduction region and the upper conduction region in the heating stage,while the area is divided into the bottom conduction region and the upper convection region in the cooling stage.In order to attain the oil temperature at any position of the tank quickly and conveniently,and to predict the oil temperature,the “Long-Stay Oil Temperature Distribution and Measurement Software” was programmed,which will contribute to the oil metering work,accurate measurement,safe and efficient production.