铅铋快堆(lead-bismuth fast reactor,LFR)与超临界二氧化碳(supercritical CO_(2),S-CO_(2))循环耦合系统是提升核能利用效率,优化核能应用现状的突破性技术。为了准确把握该系统中耦合换热这一关键问题的发展动态与现状,从中间换热器...铅铋快堆(lead-bismuth fast reactor,LFR)与超临界二氧化碳(supercritical CO_(2),S-CO_(2))循环耦合系统是提升核能利用效率,优化核能应用现状的突破性技术。为了准确把握该系统中耦合换热这一关键问题的发展动态与现状,从中间换热器技术开发、印刷电路板式换热器(printed circuit board heat exchanger,PCHE)流道优化、液态铅铋合金(liquid lead bismuth eutectic,LBE)及S-CO_(2)流动传热机理研究、LBE及S-CO_(2)耦合对流换热机理研究等角度出发,全面归纳总结了相关的实验研究与数值模拟成果。研究结果表明,Z型PCHE加工难度适中,换热性能优秀,弯折处加入直道或弯弧可在传热速率略微下降的前提下大幅降低换热器内压降,明确该型换热器是目前主流选择,并给出了PCHE的结构优化设计思路;液态LBE流动传热实验研究存在边界条件范围窄的问题,对比已有的传热预测关联式,对棒束、圆管等不同条件给出相应的传热预测关联式;对比分析适用于液态LBE的数值模拟方法,给出了可靠的利用雷诺时均方法的湍流模型与湍流普朗特数模型,阐释了利用四方程模型数值模拟的原理与优势;系统总结了应用于PCHE中的S-CO_(2)传热关联式,LBE与S-CO_(2)耦合换热研究现状与存在的问题。目前LBE与S-CO_(2)直接耦合换热的研究成果较缺乏,仍无成熟结论明确哪种换热器结构最合适,哪种数值模型有最优的可靠性与最小的偏差值,仍需针对不同应用场景具体考虑。本文明晰了铅铋-超临界二氧化碳耦合换热应用研究的方向与困难所在,对其他类似的新型多工质耦合换热系统的开发也具有重要指导意义。展开更多
The generation of highly efficient electricity and the production of massive hydrogen are possible using a very high temperature reactor （VHTR） among generation IV nuclear power plants. The structural material for a...The generation of highly efficient electricity and the production of massive hydrogen are possible using a very high temperature reactor （VHTR） among generation IV nuclear power plants. The structural material for an intermediate heat exchanger （IHX） among numerous components should be endurable at high temperature of up to 950 °C during long-term operation. Impurities inevitably introduced in helium as a coolant facilitate the material degradation by corrosion at high temperature. In the present work, the surface reactions available under controlled impure helium at 950 °C were investigated based on the thermodynamics and the corrosion tests were performed in a temperature range of 850-950 °C during 10-250 h for commercial Alloy 617 as a candidate material for an IHX. Moreover, the mechanical property and microstructure for nickel-based alloys fabricated in laboratory were evaluated as a function of the processing parameters such as hot rolling and heat treatment conditions. From the reaction rate constant obtained from an impure helium control system for a material evaluation, it was predicted that the outer oxide layer thickness, internal oxide depth, and carbide- depleted zone depth reach about 116, 600 and 1000 μm, respectively when Alloy 617 is exposed to an impure helium environment at 950 ~C for 20 years. For Ni-Cr-Co-Mo alloy, subsequent annealing and a combination of cold working and subsequent annealing following solution annealing caused increases in the grain boundary carbide coverage and size. The angular distribution of the grain boundary as well as the carbide distribution was also changed leading to a consequent improvement of the mechanical property at 950 °C in air.展开更多
基金supported by the Ministry of Education,Science and Technology (MEST) of Korea
文摘The generation of highly efficient electricity and the production of massive hydrogen are possible using a very high temperature reactor （VHTR） among generation IV nuclear power plants. The structural material for an intermediate heat exchanger （IHX） among numerous components should be endurable at high temperature of up to 950 °C during long-term operation. Impurities inevitably introduced in helium as a coolant facilitate the material degradation by corrosion at high temperature. In the present work, the surface reactions available under controlled impure helium at 950 °C were investigated based on the thermodynamics and the corrosion tests were performed in a temperature range of 850-950 °C during 10-250 h for commercial Alloy 617 as a candidate material for an IHX. Moreover, the mechanical property and microstructure for nickel-based alloys fabricated in laboratory were evaluated as a function of the processing parameters such as hot rolling and heat treatment conditions. From the reaction rate constant obtained from an impure helium control system for a material evaluation, it was predicted that the outer oxide layer thickness, internal oxide depth, and carbide- depleted zone depth reach about 116, 600 and 1000 μm, respectively when Alloy 617 is exposed to an impure helium environment at 950 ~C for 20 years. For Ni-Cr-Co-Mo alloy, subsequent annealing and a combination of cold working and subsequent annealing following solution annealing caused increases in the grain boundary carbide coverage and size. The angular distribution of the grain boundary as well as the carbide distribution was also changed leading to a consequent improvement of the mechanical property at 950 °C in air.
