钍基熔盐堆换热器的实验与数值研究

发布时间：2018-03-25 02:31

本文选题：TMSR　切入点：熔盐换热器　出处：《中国科学院工程热物理研究所》2017年博士论文

【摘要】：为发展先进的第四代核电系统,中科院于2011年启动了钍基熔盐堆核能系统(TMSR)的专项研究。TMSR系统采用高温氟化盐作为堆芯的冷却剂和二回路的传热介质,其具有固有安全性好、系统经济性高、核废物产生少、防核扩散等技术优势。以高温氟化盐(600～700℃)为工质的熔盐换热器是TMSR系统的关键部件,其对系统的经济性和安全性有重要的影响。发展大型化和实用化的熔盐换热器是TMSR系统的现实需求。然而无论是传统的管壳式还是正处于概念研究阶段的新型紧凑式熔盐换热器,其在TMSR系统中的应用中均面临着传热特性研究不足的巨大障碍。基于TMSR系统发展的迫切需求,本文开展了 TMSR系统熔盐换热器的实验和数值研究工作,通过设计和建设熔盐换热器实验系统,开展各型熔盐换热器试验件的一系列传热性能实验研究。基于实验结果,为TMSR系统的实验装置设计大型化和实用化的熔盐换热器,并借助数值模拟的手段对设计方案进行分析,以确保系统的安全性。本文第一部分完成了一套熔盐换热器实验系统的设计和建造工作。该实验系统由主熔盐回路、次熔盐回路、闭式气体循环回路和水冷循环回路组成,可以完成不同类型的熔盐—熔盐和熔盐—气体换热器的传热性能实验研究,包括传统的管壳式熔盐换热器和新型紧凑式熔盐换热器。系统设计过程中重点克服了熔盐传热系统高温运行和易冻堵的固有特性,其结构的复杂性和功能的完善性均较现有的单回路熔盐传热特性实验系统有巨大的进步。为提高系统实验结果的精度,运用不确定度理论全面科学地分析和评定了该系统的测量不确定度。评定结果表明避免在小气体流量下进行实验以及提高实验中熔盐的进出口温差是减小系统测量不确定度、提高测量精度的最有效方法。该实验系统的设计和建成,为熔盐换热器的研究和发展提供了可靠的实验平台,具有重要的科学意义。本文第二部分根据TMSR系统对管壳式熔盐换热器的近期需求,设计了三台管壳式熔盐换热器试件并分别完成了传热性能实验。该实验的完成突破了熔盐对流传热特性只集中于管内流动的研究现状,具有一定的创新性。实验结果满足热平衡要求,表明熔盐换热器实验平台具有良好的可靠性。实验分别研究了熔盐在管程和壳程的对流传热特性,分析结果表明:(1)管程熔盐在过渡流和湍流区内的对流传热特性与传统经验准则吻合良好。层流的对流传热特性实验数据较经验准则偏大30%。(2)熔盐在带折流板的壳程空间内的对流传热特性与导热油存在明显的差别,表明现有的经验设计准则可能并不适用于折流板管壳式熔盐—溶盐换热器的设计计算。(3)熔盐—气体换热器的传热热阻主要集中于气体侧,当系统熔盐泵发生停泵故障时,熔盐—气体换热器的管束中的熔盐将面临巨大的凝固堵塞风险。基于熔盐换热器实验系统的运行经验,初步讨论了系统的后续优化方案,内容包括系统布局、电加热系统以及伴热保温系统的优化。本文第三部分基于管壳式熔盐换热器试验件的实验结果,协助完成了 10 MW固态燃料实验堆空气冷却系统的设计方案。为确保空气冷却系统的安全运行,对系统的10 MW熔盐—空气换热器进行了两方面的数值研究工作。首先,通过熔盐单管内凝固实验验证了 FLUENT的SolidificationMelting模型对熔盐相变过程预测的准确性,并利用FLUENT分析了管束中熔盐在熔盐泵停泵事故工况下的凝固过程,分析结果表明熔盐泵停泵事故会在15 s内引发管束中的凝固堵塞,危及系统安全;其次,利用FLUENT的多孔介质模型解决了管束流量模拟分配所面临的网格和计算资源限制的关键问题,成功地计算了管束中的流量分配结果,计算结果表明熔盐—空气换热器的流量分配方案合理,其管束中的实际流量与平均流量偏差不超过13.14%,由于流量分配不均匀引起的熔盐过冷凝固风险较小。
[Abstract]:For the development of advanced fourth generation nuclear power system, the Chinese Academy of Sciences in 2011 launched a nuclear power system of thorium based molten salt reactor (TMSR) heat transfer medium coolant of special research on the.TMSR system using high temperature fluoride salt as the core and the two loop, which has good inherent safety, economic system of high nuclear waste, nuclear diffusion technique. At high temperature (600~700 DEG C) for fluoride molten salt medium heat exchanger is a key component of the TMSR system, which has an important effect on the economy and safety. The molten salt and the practical development of large-scale heat exchanger is the practical requirements of the TMSR system. However, no matter is the conventional shell and tube or is in the research phase of the new concept of compact type molten salt heat exchanger and its application in TMSR system are facing enormous obstacles. Lack of research on heat transfer characteristics of TMSR system based on the urgent needs of development, this paper carried out T The MSR system of molten salt heat exchanger experimental and numerical study of heat exchanger, the experimental system through the design and construction of molten salt, to carry out various types of molten salt heat exchanger test a series of experimental study on the heat transfer performance. Based on the experimental results, the molten salt and practical for the design of large-scale experimental device of the TMSR system for the heat exchanger, and the design scheme is analyzed by means of numerical simulation, in order to ensure the safety of the system. In the first part of this paper made a molten salt heat exchanger experimental system design and construction work. The experimental system consists of the main circuit of molten salt, a molten salt loop, closed loop and gas water circulation circuit, experimental research on heat transfer performance of complete different types of molten salt, molten salt and gas heat exchanger, including shell and tube type molten salt the traditional heat exchanger and a novel compact type molten salt heat exchanger. The design process of the system overcomes the key High temperature molten salt heat transfer system and is easy to be frozen the inherent characteristics, the perfection of the complexity and function of the structure are compared with the existing single loop molten salt heat transfer experimental system has great progress. In order to improve the precision of the system by using the experimental results, the uncertainty theory comprehensive scientific analysis and assessment of the measurement system uncertainty evaluation results showed that avoid in small gas flow experiment and the molten salt in the experiment is to reduce the temperature difference between inlet and outlet of the system measurement uncertainty, the most effective way to improve the measurement accuracy. The system designed and built, provides a reliable experimental platform for research and development of heat exchanger for welding salt, it has important scientific significance. In the second part, according to the recent need for shell and tube type molten salt heat exchanger TMSR system, designed three sets of shell and tube heat exchanger with molten salt samples and complete the transfer of Can the experiment. Research status of the experiment to complete breakthrough molten salt to focus only on the convective heat transfer characteristics of pipe flow, has certain innovation. The experimental results meet the requirements of heat balance, showed that the molten salt heat exchanger experimental platform has good reliability. The experiment studied the convective heat transfer characteristics of molten salt in the tube side and shell in the process, analysis results show that: (1) convection heat transfer tube of molten salt in transition and turbulent flow in the region and the traditional empirical criterion are in good agreement with the experimental data. The characteristics of laminar convection heat transfer is relatively large 30%. experience. (2) there are obvious differences of convective heat transfer characteristics and the heat conducting oil in molten salt with a baffle in the shell space, that experience of existing design guidelines may not apply in design of pipe shell type molten salt - soluble salt in the calculation of heat exchanger baffle. (3) the thermal resistance of molten salt - gas heat exchanger mainly focused on the gas side, when the Department of The molten salt pump pump failure, the molten salt bundle of molten salt - gas heat exchanger in will face a huge risk of clogging. The operation experience of solidification of molten salt heat exchanger experimental system based on the preliminary discussion of the subsequent optimization scheme of the system, including system layout, optimization of the electric heating system and with the heat insulation system. The third part of shell and tube heat exchanger experimental results for molten salt based on test pieces, to help complete the design of air cooling system of 10 MW solid fuel reactor. In order to ensure the safe operation of air cooling system, a numerical study on the two aspects of the work of the 10 - MW molten salt system the air heat exchanger. First of all, the FLUENT SolidificationMelting model on the accuracy of the phase change process of molten salt prediction is verified by experimental solidification of molten salt tube and analyzed by FLUENT molten salt pump tube bundle in molten salt pump engineering accident The solidification process under the conditions of the analysis showed that the molten salt pump stopped pumping accident will cause the solidification in the bundle block within 15 s, endanger security of the system; secondly, using porous media FLUENT model solves the key problem of grid computing resource allocation and the limits of the simulation of tube bundle flow, successfully calculated the flow distribution in the bundle, the calculation results show that the molten salt air heat exchanger flow distribution scheme is reasonable, the bundle in the actual flow and the average flow rate deviation is less than 13.14%, because the molten salt flow distribution caused by uneven cooling of solid risk is small.

【学位授予单位】：中国科学院工程热物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL353.13;TL426

【相似文献】