【作者】 李阳；

【导师】 汪荣顺；

【作者基本信息】 上海交通大学 ， 制冷与低温工程， 2012， 博士

【摘要】 低温绝热气瓶作为一种储运低温液体的特种容器,目前开始被广泛应用于机械、化学工业和国民经济各领域,取代传统的高压气瓶用以提供工业气体。由于低温绝热气瓶可以带压储存和运输低温液体,因此与普通压力容器相比结构更为复杂。其绝热性能和安全性是低温绝热气瓶高效可靠使用的保证,研究绝热结构的传热机理、强度分析以及合理有效的优化方法具有重要的理论意义和实用价值,同时,建立合理的评估绝热性能的标准对于促进低温技术的发展和应用有重要的意义。因此,本文以传热学、数值分析和有限元等理论为指导,建立传热模型与热力耦合模型,采用ANSYS有限元分析软件进行分析,研究低温绝热气瓶绝热结构优化。同时,对日蒸发率的影响因素和修正关系式进行了探讨,主要进行以下几方面研究:(1)作为低温绝热气瓶内外容器之间的重要支撑结构,使得通过颈管进入低温绝热气瓶的热流占总热流的比例非常大,甚至达到一半以上。为此,采用实验和数值模拟相结合的方法,分别建立低温绝热气瓶颈部传热的稳态导热模型和共轭传热模型,与实验的结果进行比较,得到模型的误差最大分别为8.91%和5.66%,并且充装的低温液体越多,精度也越高,因此考虑实用性以及计算效率等多方面因素,稳态导热模型在相对误差的范围内对颈部传热的分析精度足够,并以此模型对两种高径比H/D分别为2.61和1.94的低温绝热气瓶颈部传热进行分析。(2)根据低温绝热气瓶的结构特性,建立了强度分析的热力耦合模型,对H/D分别为2.61和1.94的低温绝热气瓶在承受静态载荷及2g的冲击载荷工况下的热应力进行了分析,确定在颈管接管头与封头开孔连接边缘的环向面是应力水平最高的部位,也是整个气瓶的最薄弱部位,并采用等效线性化的处理方法对颈管开孔边缘最危险截面的不连续应力进行分类处理。(3)将上述建立的稳态导热模型和热力耦合模型两种模型到引入到颈管的优化分析中,分别对颈管结构的长度、直径和壁厚在不同无量纲参数(h/H、d/D、δn/δ)下对通过颈部的漏热量及最大热应力的影响进行了研究,对颈管结构从传热及强度两方面进行了优化,找出最优化的尺寸参数,并且探讨了颈管开孔结构补强的重要性,对低温绝热气瓶颈管的结构设计提供理论依据,并且有着重要的指导作用。(4)日蒸发率作为评价低温绝热容器绝热性能最重要的技术参数,能够非常直观的反映气瓶的绝热性能,一直受到非常多的关注,因此准确测量和计算低温容器的日蒸发率至关重要。本文以立式低温绝热气瓶为基础,采用数值模拟与实验验证的方法,对包括环境温度、环境压力和液位高度对日蒸发率的影响因素进行研究,并且分析研究更合理更准确的修正方法来对低温绝热气瓶的静态日蒸发率进行计算,为国家标准GB/T 18443《真空绝热深冷设备性能试验方法》的修订提供了数据支持。本文的研究方法和结论使低温绝热气瓶的设计更加合理化,为推广和发展低温绝热气瓶的应用提供了理论基础和工程应用价值。更多还原

【Abstract】 As special cryogenic liquid storage and transportation container, the cryogenic insulated cylinders are widely used in many fields, especially in the machinery, chemical industry, and national economy areas to replace the high pressure gas cylinders for supplying industrial gasses. The structure is more complicated compared with ordinary pressure vessel because of the pressured storage and transportant. The thermal insulating properties and security is an assurance of efficiency and operational reliability.The study onheat transfer mechanism, stress analysis and reasonable effective optimization method for thermal insulating construction is of theoretical significance and practical,andestablishing rational evaluation standards of thermal insulating properties have important significance on promoting the development and application of cryogenics technology.Therefore,the heat transfer models and thermal-mechanical coupling model established in this thesis by guidance of heat transfer theory, numerical analysis and theory of finite element anylysis, and the finite element analysis software of ANSYS has been utilized to analyzethe constructionoptimization forthermal insulating constructionof cryogenic cylinder. Further exploration for influence factors and correction relation of daily evaporation rate is also made in this thesis. Several studies of this thesis are summarized as follows:(1) As an important support structure between inner and outer vesselin cryogenicinsulated cylinders,the heat flux from the outside environment through the neck tube into the cryogenic liquid occupies a great proportion of the total heat leak and can be more than half of the total heat loads. By using the mothed of experimental combined the simulation, the steady-state conduction model and conjuage heat transfer model have been established, andthe performance deviation compared with experiment results is within8.91% and 5.66% respectively. The more cryongenic liquid filled, thehigher the accuracy.So considering the effect of practicality and computational efficiency, the accuracy of steady-state conduction model is high enough for heat transfer through necks. The necks of cryogenic cylinder with height-to-diameter ratio of 2.61 and 1.94 have been analyzed basing on that model.(2) The thermal-mechanical coupling modelhas been establishedbasing on structural properties of cryogenic cylinder. The thermal stresses of cryogenic cylinder with height-to-diameter ratio of 2.61 and 1.94 under the static load and impact load have been analyzed respectively.The position with the highest stress level has been confirmed which is along theedge of opening on head, and the root of neck tube becomes the weakest link. The tress classification of discontinuity stress in most dangerous section has been also analyzed byusing the method of equivalent linearization.(3) The optimization analysisof neck tube is based on the above two models ofsteady-state conduction model and thermal-mechanical coupling model.The effect of dimensionless parameters with h/H,d/D andδn/δon heat flux through the necks and the max thermal stress have been researched, so the optimization analysis of neck is reviewed from two aspects of heat transfer and strength to find out the optimaldimension parameter. And the importance of opening reinforcement has been discussed.The study result has guiding significance for design and application of cryogenic cylinders.(4) As an important technology parameter to evaluate the thermal insulating properties of cryogenic cylinders, daily evaporation rate which is attracting more attention can intitively reflect the thermal insulating properties of cryogenic cylinders, so the accurate measurement and calculation of daily evaporation rate for cryogenic cylinders is very important. This thesis researches the influencing factores of daily evaporation rate which includes environmental temperature, environmental pressure and liquid height by using numerical simulation mothed and experimental.And the more accurate more reasonable correction methods are put forward to calculate daily evaporation rate which can provid the data support for revision of national standard GB 18443《Testing method of performance for vacuum insulation cryogenic equipment-Part 5: Static evaporation rate measurement》The research method and conclusion of this thesis makes design of cryogenic cylinders more rational, and provides theoretical basis and engineering value for design and application of cryogenic cylinders.更多还原