High vacuum multilayer insulation (HV-MLI) cryogenic pipes which are used to transport low-temperature media (e.g.LNG) are often in a cryogenic environment with internal fluid pressure,so they will bear complex loads due to the effect of thermal-structural coupling.For investigating the response of each part in an HV-MLI cryogenic pipe under complex loads,the thermal-structural coupling finite element model was established based on a certain L-shape HV-MLI cryogenic pipe of horizontal-vertical trending.Then,the distribution of pipe temperature fields in different operating conditions,and the stresses on inner tubes,outer tubes,thermal bridges,bellows and thermal insulation supports and their variation in different loads were calculated.The following findings were obtained based on the above mentioned analysis.First,thermal insulation supports and thermal bridges are the main parts that affect heat leakage of pipes.In the case of LN2 transportation,for example,the heat leakage at thermal insulation supports and thermal bridges accounts for about 49.07％ and 49.32％ of the total pipe heat leakage,respectively.Second,inner tubes,outer tubes,elbows and thermal bridges are very safe when they are in service since their stresses are relatively small and lower than the material yield limit.Third,the stress on bellows increases with the decrease of the transportation medium temperature and the increase of compensation inner tube length.The bellow in a horizontal section is the most dangerous part of the whole pipe due to its higher stress.And fourth,the internal pressure on inner tubes is the main factor impacting the stress of thermal insulation supports.With the increase of the internal pressure on inner tubes,the stress on thermal insulation supports in horizontal and vertical pipe sections,which is the closest to the elbow,increases significantly,but the stress on thermal insulation supports,which is far away from the elbow,doesn't change greatly.Therefore,it is necessary to increase the thickness of thermal insulation supports close to the elbow and reduce the thickness of thermal insulation supports far away from the elbow in order to guarantee the strength as well as to reduce heat leakage.%用于输送LNG等低温介质的高真空多层绝热(HV-MLI)低温管道常处于深冷环境且要承受流体内压,在热-结构耦合作用下的受力较为复杂.为了研究HV-MLI低温管道各部件在复杂载荷作用下的响应状况,以某水平—竖直走向的L形HV-MLI低温管道为例,建立了热-结构耦合分析有限元模型,计算得出了不同工况下的管道温度场分布情况,以及管道中内管、外管、热桥、波纹管和绝热支撑上的应力及应力随各载荷的变化关系.分析结果表明:①绝热支撑和热桥是影响管道漏热量的主要部件,以输送LN2为例,通过上述两个部件的漏热量分别占管道总漏热量的49.07％和49.32％;②内管、外管、弯头及热桥等部件应力较小且低于材料屈服极限,实际使用过程中不易发生危险;③波纹管应力随输送介质温度的降低和补偿内管长度的增加而增大,水平管段波纹管的应力较高,是管道中的危险部件;④内管所受内压是影响绝热支撑应力的主要因素,随内管内压的增大,水平管段与竖直管段中离弯头最近的绝热支撑应力大幅增加,而远离弯头的其他位置处的绝热支撑应力变化不大,因而可适当增加离弯头最近的绝热支撑厚度,同时减少远离弯头处支撑的厚度,以便在保证强度的同时减少漏热量.
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