规模生产的铀浓缩工厂通常用六氟化铀作为铀同位素分离的工艺介质。六氟化铀的收集和转移处理的过程，也就是在一定的工艺技术条件下，用特定的容器、工艺装置以及辅助设施通过蒸发、凝华、液化、凝固的物理变化，实现六氟化铀的气态、液态、固态的相变过程。六氟化铀在容器中的相变过程和传热机理是六氟化铀工艺系统设计、六氟化铀用设备设计、生产运行管理以及有关的科研工作的基础。目前，国际上铀浓缩工厂的取料方法常用的是气体六氟化铀在容器中凝华的物料收集工艺方法。本文分析认为，气体六氟化铀在冷冻容器中从气体到凝华为温度较低固体的过程，分为二个阶段：气体六氟化铀的降温，释放显热的强制对流换热阶段；气体分子在容器的冷却内壁及隔板上凝华成固态，释放潜热。在这两个阶段中所释放的热量经固体料层、容器壁面传递到容器外的冷却介质，完成传热过程。气体六氟化铀在容器中凝华的总传热系数取决于传热途径的三个环节：气体六氟化铀在容器中冷表面上的凝华换热过程；凝华热经固体料层、容器壁面的热传导过程；容器外壁与冷却介质的换热过程。本文对美国学者汤普逊（W.J.Thompson）就六氟化铀收集的方法和理论观点进行了分析，通过一定的条件假定，利用传热学中热阻的概念建立了相应比较简单的传热模型。由于本课题所采用的试验和铀浓缩生产的取料工艺过程是浸容式换热过程，其过程和原理与反应釜夹套中的流体换热过程相近，所以引用热交换器设计中的相关内容并且通过所建立的传热模型，利用生产和试验数据进行了传热计算，计算了气体六氟化铀凝华过程中的料层厚度、换热系数和六氟化铀固体的导热率；分析了假设条件对计算结果的影响。从气体六氟化铀在容器中收集的工艺环境和工艺方法、收集六氟化铀用容器的结构特点等方面，本文对实际应用的计算结果与美国学者汤普逊计算结果间的差异、本文中各次计算结果间的差异等方面进行了定性分析说明，并提出相应的观点。
The uranium enrichment plants, where production is on certain scale, commonly use uranium hexafluoride as working medium for uranium isotope separation. The collection and transfer process of uranium hexafluoride is also a process, which is to achieve uranium hexafluoride in gaseous, liquid and solid states to be changed through evaporating, freezing, liquefying and concreting under certain technical processing conditions, with the specific vessels, the technical processing installments as well as the appendix facilities. The uranium hexafluoride states and the heat transfer mechanism in the vessel are the foundation for designing uranium hexafluoride technical processing systems, uranium hexafluoride equipments, the production managements as well as the related scientific research works. At present，the technique of freezing uranium hexafluoride gas in the vessels is widely used in the uranium enrichment plants all over the world.The process of uranium hexafluoride gas in the vessel being frozen from gas to low temperature solid can be divided into two stages: reducing uranium hexafluoride gas temperature, releasing manifested heat. This is counter-flow heat transfer stage; Then freezing the gas into solid state on the vessel cooling wall and the partition board, and releasing latent heat. The quantity of heat released in these two stages passes through the solid material layer, the vessel wall surface and then transmits to the cooling medium outside of the vessel. The whole heat transfer process is then completed. The total heat transfer coefficient of uranium hexafluoride gas frozen in vessel is decided by three heat transfer ways: heat transfer process of uranium hexafluoride gas frozen on cold surface in vessel, heat conduction process through solid layer and vessel wall, heat transfer process between vessel wall and cooled medium outside of vessel.This thesis analyzed the viewpoint of American scholar W.J.Thompson on uranium hexafluoride collection ways. Under some assumptions, and with the help of thermal resistance concept, corresponding simplified heat transfer model has been established. Because the experiment and production technical process in taking uranium hexafluoride of this research is a kind of heat transfer process of vessels being soaked, its process and the principles are similar to fluid heat transfer process in the retort sheath. In this thesis, the actual heat transfer computation has be carried out by using the production and experiment data, using related contents of heat exchanger design and the established heat transfer model in this thesis. Also those being calculated include the material layer thickness of uranium hexafluoride gas freezing process, the heat transfer coefficient and the uranium hexafluoride solid thermal conductivity. Influence of assumed conditions to the computed results, differences between the practical application result computed and W.J.Thompson’s result are analyzed by investigating the process conditions and techniques of uranium hexafluoride gas, the vessel characteristics etc..The computation results difference is analyzed too. Qualitative analysis explanation and independent viewpoints are presented.
