Research On Influence Factors Of Evaporation Rate Of Independent C-type Storage Tank For LNG Ships

In recent years,with the promotion of new energy,the use of clean energy is expanding to an unprecedented level.Liquefied natural gas(LNG)is one of the cleanest and most widely used energy sources worldwide,it has a broad application prospect in the future.To ensure the safe and efficient transportation of LNG,usually the LNG is cooled to-163℃,liquefied and then transported by LNG ship usually.During ship transportation,the LNG in the tank will evaporate due to external heat transfer,The boil of gas(BOG)generated will not only be wasted,it also affects the safety performance of LNG independent C-type storage tank.Ensuring the safe transportation of LNG in independent C-type tanks,it is of great significance to study the steady-state temperature field and evaporation rate of the independent C-type tank of LNG carrier.Therefore,the steady-state temperature field and boil rate of an independent C-type tank of an LNG carrier are studied in this thesis.(1)Describes the thermodynamic properties and migration properties of LNG,and gives the calculation formula and method of LNG-related properties.Based on the principle of heat transfer,the steady-state temperature field theory is described in detail,and then the heat conduction differential equation is given,and the boundary conditions of temperature field are briefly classified.(2)The evaporation rate test of 1.5m~3independent C-type tank is carried out.The boil performance of small C-type tank is measured and calculated by weighing method.Based on monitoring and analyzing test data,the calculation model of the boil rate of the experimental storage tank is established.The daily boil rate of the storage tank is obtained by calculating the boundary heat flux,and the data are compared with those of the test,which verifies the accuracy of the numerical calculation model.(3)Based on the traditional calculation method,the heat conduction between the tank and the outside world is the main reason affecting the evaporation rate of the tank.The heat conduction value of each part of 2550m~3C-type storage tank was calculated by numerical simulation.to calculate daily evaporation rate of the 2550m~3C-type tank.And through the saturated homogeneity model,The static daily evaporation rate and storage time of the tank under different internal pressures are calculated.The results show that different internal pressures do not change the static daily evaporation rate of the C-type tank,However,increasing the design pressure can effectively improve the safe storage time of the C-type tank.The fourth part of this thesis is based on univariate control method,the effects of different temperatures,convective coefficients,insulation thickness and insulation thermal conductivity on evaporation rate of 2550m~3C-type tank are studied respectively.Finally,the laminated wood for the saddle of the 2550m~3C-type tank is selected,and two different insulation materials are selected to compare,to further reduce the daily evaporation rate value of the 2550m~3C-type tank is optimized.