Analysis Of Lossless Storage And Transportation Performance In LNG Storage Tank

With the increasing prominence of energy and environmental issues,natural gas as a new type of clean energy has received widespread attention from countries.At present,there are mainly two ways for the transportation of natural gas:pipeline transportation and LNG storage and transportation.As technology matures,storage and transportation of LNG tanks have been widely used.As natural gas is a flammable and explosive chemical,leakage during storage and transportation can cause serious consequences.Therefore,it is necessary to study the lossless storage and transportation process of LNG and to analyze the factors that affect the pressure rising rates in the lossless storage and transportation process,so as to effectively control the pressure rise in the storage tank.The main research work of this paper is as follows:(1)According to the data of physical property parameters,the polynomial fitting of the thermal parameters of the low-temperature LNG and other fluids with temperature changes was performed using MATLAB software;on this basis,mathematics was established for the gas-liquid two-phase flow,heat transfer and evaporation process in LNG storage tanks.Analyze the model,perform UDF programming on the evaporative condensation source equations involved,and import FLUENT software to establish a CFD analysis model for direct simulation of lossless storage and transportation of cryogenic liquids;a lossless storage and transportation process for 250 m~3 horizontal liquid nitrogen storage tanks.The experimental results verify the correctness of the established simulation analysis model.(2)Using the established CFD analysis model,the initial thermal response of a 250 m~3horizontal LNG storage tank was first simulated,and the temperature,flow field,pressure distribution and regularity of the initial stage of the storage tank under external heat leakage conditions were obtained.The temperature and pressure curves from the initial state to the vapor-liquid equilibrium were obtained,and the formation of RB convection in the storage tank and the influencing factors were analyzed.The CFD model was used to simulate the lossless storage and transportation processes of different initial fill rates,different heat flux densities,and different sizes of storage tanks.The intuitive cloud diagrams and variations of flow field,temperature,and pressure distribution in the tank during storage and transportation of LNG were obtained.Through the simulation and comparison of the lossless storage and transportation process under different conditions,the influence of the internal diameter of the tank,the heat flux of the leakage heat,and the initial filling rate on the lossless storage time was revealed.(3)The temperature and pressure during the lossless storage and transportation of the250 m~3 horizontal LNG storage tank were further calculated using the traditional thermodynamic model.The lossless storage time were calculated by the three models of saturated homogeneous model,homogeneous surface evaporation model and three-zone model.By comparing with the CFD simulation results,the deviations between the calculation results and the actual results of the thermodynamic models and the causes of the deviations were analyzed.(4)Based on the results of CFD simulation,as well as the effect of tank internal diameter and heat flux on lossless storage time,a new fast calculation model for lossless storage time was established.The reliability of the model was verified by two examples.This provided great convenience for calculating the lossless storage time.