Research On Heat Transfer And Evaporation Rate Of C-Type Storage Tanks For LNG Ships

Over the years,natural gas has been widely used as a clean energy source.Onshore LNG transportation is mainly through pipelines and transport vehicles.Because of the cost and difficulty of pipeline laying,LNG carriers have become the mainstream of LNG marine transportation.LNG carriers usually use cryogenic liquid storage tanks to store liquid natural gas.During the transportation process,the external environment of the LNG tank will change with the route.Because of the different external environment,the tank will absorb different heat result in part of the liquid evaporating.Internal pressure increases and LNG has the characteristics of flammable and explosive,which may cause safety hazards.And evaporating too much LNG can also increase transportation costs.The thermal insulation performance of LNG tanks is of great significance for the safe transportation of LNG carriers.Therefore,the temperature field and evaporation rate of independent C tanks are studied in this paper.The following are the main contents of this paper.The first part of this article first gives a brief overview of the thermodynamic properties of LNG.Being able to accurately calculate various parameters of thermodynamic properties is of great help in the study of thermodynamic processes.The formula related to the calculation of thermodynamic properties is given.The calculation of the migration properties of natural gas is then described.The nature of the migration of natural gas,ie,transmission characteristics,is a fundamental parameter for natural heat transfer calculations and flow calculations.The calculation formula for some of the migration properties of LNG is then given.Finally,the thermal analysis principle of the steady-state temperature field is introduced,including the characteristics of thermal analysis,thermal analysis unit,thermal load and boundary conditions.The second part of this article first gives an overview of the specific process of ANSYS thermal analysis and gives the differential equation of thermal conduction.Based on the experimental results,the evaporation model of the LNG tank was analyzed and compared with the experimental results.The prediction method of evaporation rate of LNG liquid storage tank was put forward,and finite element analysis was performed.The evaporation rate of some LNG liquid storage tanks was obtained.In the third part of this paper,firstly based on the steady-state temperature field theory,the 6000m~3LNG liquid storage tank was numerically analyzed,the heat distribution was obtained,and the corresponding evaporation rate of the 6000m~3LNG liquid storage tank under different ambient temperature conditions was predicted with the influence of heat radiation.And the result is compared with the evaporation rate without considering the heat radiation.Secondly,the formula of evaporation rate is summarized and the static evaporation rate of the storage tank is calculated.The static evaporation rate of different internal pressures of the6000m~3LNG liquid storage tank is deduced and calculated.The law of evaporation rate under different internal pressures was obtained.Finally,using saturated homogenization model,the static natural boost pressure and storage time of LNG were studied and calculated.The law of storage time under different design pressure and different external temperature was studied.The fourth part of this paper is based on the theory of gas-liquid equilibrium and uses Aspen Hysys software to study the pressure of LNG storage tanks.First,the model for static evaporation in LNG tanks was established,and the structural unit throttle valve and separator(storage tank)were briefly introduced.Secondly,the Hysys dynamic model of static evaporation of LNG storage tanks and the corresponding simulation methods and working conditions are given.Finally,the influence of the pressure change in the tank,the influence of different LNG components on the pressure in the tank,and the influence of different filling rates on the tank pressure are analyzed.The content of this paper has certain reference value for the heat transfer and evaporation of the LNG ship’s independent type C tank.