低温热阱环境下超临界二氧化碳动力循环概念设计研究

Optimization Design Research of Supercritical Carbon Dioxide Power Cycle under Low-temperature Heat Sink Environment

针对低温热阱应用环境下的核能动力转换系统,在简单回热循环和再压缩循环的基础上进行了冷端优化设计研究,根据循环冷端工质压缩状态的不同,提出了3种冷端优化方式。研究建立了热力学分析程序,并验证了热力学分析程序的准确性。使用程序针对100 MW规模发电机组分别对透平入口温度为550℃的中高温反应堆热源和温度为315℃的中低温反应堆热源进行了计算分析。研究发现,冷端优化后的超临界二氧化碳(S-CO_(2))动力循环系统运行压力降低,循环效率提高了2%~4%。S-CO_(2)动力循环冷端优化构型在具有低温热阱的核能动力转换应用中具有较好的应用前景。

This paper presents a cold-end optimization design study of a nuclear energy power conversion system in the context of low-temperature heat sink applications.Based on the principles of simple recuperation cycles and recompression cycles,the study focuses on the supercritical carbon dioxide power cycle and its cold-end optimization for application in low-temperature heat sink environments.These strategies are designed to enhance the efficiency and reduce the operating pressure of the supercritical carbon dioxide power cycle under low-temperature heat sink conditions.Three different cold-end optimization approaches were proposed,which include:a non-condensing liquid-phase compressed supercritical carbon dioxide power cycle,a condensing liquid-phase compressed supercritical carbon dioxide power cycle,and a gas-phase compressed supercritical carbon dioxide power cycle.This research established a thermodynamic analysis program,which modeled turbine machinery such as compressors and expanders using isentropic models.Heat exchangers such as recuperations and coolers were simplified and modeled,with pressure drops and end temperature differences assumed.The study’s thermodynamic analysis program was compared with computational results from a Sandia National Laboratories research report,confirming the accuracy of the thermodynamic analysis methodology presented in this paper.For a 100 MW scale power generation unit,the thermodynamic analysis program was used to conduct computational analyses on both simple recuperation cycles and recompression cycles.These cycles were driven by a medium-to-high-temperature reactor heat source with a turbine inlet temperature of 550℃,and a medium-to-low-temperature reactor heat source with a turbine inlet temperature of 315℃.The study reveals that the optimal cold-end optimization approach varies based on the heat source temperature and cycle configuration.For the medium-to-high-temperature reactor heat source,the gas-phase compressed supercritical carbon dioxide power cycle in the simple recuperation cycle configuration achieves the highest efficiency at 39%.In the recompression cycle configuration,the condensing supercritical carbon dioxide power cycle achieves the highest efficiency at 48%.For the medium-to-low-temperature reactor heat source,regardless of the cycle type,the condensing supercritical carbon dioxide power cycle yields the highest efficiency,the highest efficiency is 28% for the simple recuperation cycle and 33% for the recompression cycle.When comparing the cold-end optimized supercritical carbon dioxide power cycle to conventional supercritical carbon dioxide power cycles with the same maximum temperature and pressure,the optimized system exhibits a reduction in operating pressure drop and an efficiency improvement of 2% to 4%.The cold-end optimized configurations of the supercritical carbon dioxide power cycle hold promising applications for nuclear energy power conversion systems with low-temperature heat sink environments.