基于ADS系统的液态铅铋和氦气换热不可逆性分析及热力学优化

The heat transfer between the liquid lead-bismuth eutectic and helium gas is studied from the viewpoint of second law of thermodynamics in the present research project. The irreversible losses of heat transfer between liquid lead-bismuth and helium gas are numerically investigated at component level, and the distribution regularities of local entropy generation and local entransy dissipation are analyzed to reveal the existence of the optimal thermodynamic trade-off. Afterwards, the optimization of main heat exchanger in which the liquid lead-bismuth is cooled by helium gas is mainly studied based on the Accelerator Driven Sub-critical (ADS) System, and the optimization of heat exchanger would be developed from the component level to the system level. The optimization of main heat exchanger in the ADS system is conducted based on the entropy generation minimization principle and entransy dissipation extremum principle, and the performance evaluation criterion of heat exchanger which is suitable for the ADS system would be proposed through analyzing the influences of different optimization objectives on the global performance of the system in the present project. The aim of the present project is to elucidate the distribution regularities of irreversible losses in the heat transfer between liquid lead-bismuth and helium gas at the component level, realize the optimization of main heat exchanger in the ADS system at the system level, further validate and extend the entransy dissipation theory which was proposed by Chinese scholars, and establish theoretical foundation and provide technological support for the design of ADS system and the optimization of main heat exchanger.

本项目从热力学第二定律的角度对氦气和液态铅铋合金传热过程进行研究。首先在部件层面数值研究液态铅铋和氦气传热过程的不可逆性损失，明确局部熵产和局部（火积）耗散率的分布规律，揭示换热器最佳热力学平衡点的存在性规律。然后着重于基于加速器驱动次临界（ADS）系统的氦气冷却液态铅铋主换热器的优化，将目前以部件层面为主的换热器优化推广到系统层面。基于熵产最小和（火积）耗散极值原理等对ADS系统的主换热器进行优化，通过对比和分析不同优化目标函数对系统整体性能的影响，总结出适用于ADS系统的换热器评价指标。该项目的目的是在部件层面阐明氦气冷却液态铅铋换热过程的不可逆损失分布规律，在系统层面实现ADS系统主换热器的热力学优化，同时进一步检验和推广我国学者提出的(火积)耗散理论，为ADS系统的设计和主换热器的优化奠定理论基础和提供技术支撑。

本项目以加速器驱动次临界洁净核能系统（ADS）先进二回路为背景，主要研究了液态铅铋与氦气传热流动特性和换热器优化设计方法及评价标准。首先通过考察多种换热器确定了液态铅铋-氦气主换热器形式及流动布置方式，并开展了多参数优化。进一步在系统层面对主换热器、氦气回路回热器和冷却器进行了多参数优化，将部件层面优化发展到系统层面。以氦气布雷顿做功系统为背景，分析了主换热器、回热器、冷却器等多个部件对系统性能的影响机理，揭示了系统内多个换热器间相互匹配与协同优化的机制与规律。调研了多种系统层面换热器优化的评价标准，阐述了多种评价标准间的内在联系以及对系统性能的影响规律。研究了适用于液态铅铋的湍流普朗特数模型，确立了精确可靠的液态铅铋数值模型。数值研究了液态铅铋传热流动过程中熵产及（火积）耗散的分布规律，分析了传热及阻力不可逆损失间的相互作用机制，探讨了随温度变化的物性对传热及阻力不可逆损失的作用规律。阐明了折流板间距及缺口高度等对壳侧氦气传热及压降的影响规律。通过廊坊搭建的相关实验平台对部分结果进行了验证。本项目为ADS系统的建设和换热器的优化设计奠定了理论基础和提供了技术支撑。