Study On Structural Strength,stability And Heat Transfer Performance Of Vertical LNG Cryogenic Storage Tank

As having strong pressure-bearing capacity and prominent insulation performance,LNG cryogenic storage tanks are widely used in industrial productions.Compared with ordinary storage equipment,the structure and operating conditions of cryogenic storage tanks are more complex,and the design requirements are more stringent.Therefore,both the strength requirements and thermal insulation performance requirements of the tank have to be considered for the design of cryogenic storage tanks.In this thesis,finite element method was used to simulate the structural strength and stability of a medium-sized cryogenic storage tank,and the stress classification methods were used to perform the strength assessment.The structural optimization design of the reinforcing rings for the outer vessel of the cryogenic storage tank was carried out.At the same time,the thermal insulation performance of the tank was studied.The leakage heat and static evaporation rate of the tank were calculated with numerical simulation method.The structure of centralized leakage heat was improved.The main work and results are listed below.(1)The load of CFL-54/1.2 cryogenic storage tank was calculated,and the structural static analysis module of ANSYS Workbench was used to analyze the stress of the tank under the operating condition and the hydraulic test condition respectively.Strength assessment was completed conforming to According to JB4732-1995 Steel Pressure Vessels-----Analysis Design Code.(2)The steady-state heat transfer model and radiation model of cryogenic storage tank was established using ANSYS Workbench.The leakage heat and static evaporation rate of the tank were calculated with numerical simulation method.(3)The sub-model analysis method was used to analyze the concentrated heat leakage structure of the cryogenic storage tank,and the steady-state heat transfer sub-models of the support tubes,the circumferential support tubes and the outlet tubes of the storage tank were established.The heat transfer parameters of the three sub-models were analyzed and the sub-model structures were improved based on reducing the heat leakage.As a result,the static evaporation rate of the tank is reduced by 8.925%after the sub-model structure improvement.(4)The eigenvalue buckling analysis and nonlinear buckling analysis were carried out for the outer vessel of the cryogenic storage tank,and the safety factor and critical buckling load of the outer vessel of the cryogenic storage tank are obtained.In order to enhance the anti-instability ability of the outer vessel,the multi-objective driving optimization analysis method was conducted to optimize the reinforcing rings under the given requirements for the critical buckling pressure.The weight of the equipment was reduced,and the optimal design of the outer vessel and the lightweight design of the equipment were realized.(4)The limit load analysis of the outer vessel of cryogenic storage tank was carried out with ANSYS Workbench.The results show that the optimized outer vessel still meets the strength requirements of JB4732-1995 Steel Pressure Vessels-----Analysis Design Code.