Research On Direct Analysis Method Of Temperature Field And Temperature Stress Distribution In Membrane LNG Carrier Tank

In the world,with the increasing demand for natural gas,LNG carriers have broad market prospects.When LNG carrier is loaded with LNG,the lowest temperature of it reaches-163~oC.Low temperature conditions will affect the mechanical properties of ship hull steel.The temperature difference between LNG carrier and external environment is large,and it will also produce large temperature stress.Therefore,in the design stage of LNG carrier,it is necessary to predict the temperature field and analyze the temperature stress to ensure the safety for its transportation.At present,A simplified algorithm is mainly used to calculate the temperature field of LNG liquid tank.When calculating the natural convection heat transfer in the cavity,the experimental correlation of large space natural convection heat transfer is used to simplify the calculation,which is difficult to ensure the accuracy of calculation.At the same time,this method can not calculate the cavity air temperature distribution.Based on CFD and FEA simulation,this paper presents a direct method for predicting the temperature field and temperature stress distribution of the LNG liquid tank.The temperature field and temperature stress distribution of a 147000m~3 membrane LNG carrier are calculated.The results are compared with those calculated by the simplified algorithm.The comparison shows that the CFD method can more accurately describe the temperature field of the LNG liquid tank,and has higher accuracy in solving the temperature distribution of the air in the cavity.Firstly,the natural convection heat transfer in the cavity is studied based on CFD simulation.The results are in good agreement with the reference values.On this basis,the conjugate heat transfer of typical cavity bulkhead structure is analyzed,and the accuracy of CFD method is verified.Then,based on CFD and FEA simulation,the temperature field and thermal stress distribution of the LNG liquid tank of a 147000m~3 membrane LNG carrier are calculated.Finally,the simplified algorithm is used to calculate the same LNG liquid tank,and the results of the two methods are compared and analyzed.The research content of this paper can provide some reference for the design stage of membrane LNG carrier,and has certain reference significance for the temperature field prediction of other temperature sensitive ships(asphalt carrier,floating nuclear power plant).