The Temperature Field,Thermal Stresss Analysis Of FLNG Carrier Tank And Its Impact On Strength

Large FLNG is a new novel floating production device which is used to exploit and store kinds of ocean natural gas.First,With subsea gas recovery system,it can exploit deep-sea gas production,then by oil and gas water treatment,the natural gas transfer to liquefaction and to store LNG.Finally,LNG ship convy LNG to overland.As it can obtain cost-effective exploiting of ocean natural gas,some research institutes have launched related research projects.Different from traditional LNG ship,FLNG has a double bottom,double shell side,double deck.Besides,it has a strong double-decker bulkhead without big opening.These characters make it have high bending and torsion stiffness.It adopts membrane liquid cargo to store liquid natural gas(LNG),and the storage tanks require good insulation and tightness as they are under low temperature conditions.At the same time,considering the temperature difference and the traits of double cargo,it is necessary to analysis the effects of thermal Stress.First,based on fundamental theories of thermodynamics,heat conduction and transfer are investigated for complex geometries.By By analyzing the heat transfer of simplified structure of FLNG carrier,the heat convection coefficient and inhull temperature were calculated by thermodynamics method.Then a three-cabin model of FLNG is established and the temperature fields of the model are studied under different conditions using commercial finite element analysis software MSC/PATRAN.Taking into account the structure characteristics of insulation,the temperature fields are analyzed under the conditions that the primary barrier is broken and the heater is failure.Then combined theory with engineering practice,the influence of thermal stress on the hull structure is analyzed on the basis of the temperature field.In addition,the thermal stress are analyzed under the conditions that the primary barrier is broken and the heater is failure.At last,FLNG will be subject to various external forces as serving in complicated environments.So it’s necessary to apply the design loads(which are calculated by the specification of of FLNG’s cargo containment system)and the temperature load to study the strctural safety of FLNG.It is expected that the method in this thesis could be helpful for future work on structural safety problem under low temperature.