Session: 04-05: SMRs, Advanced Reactors and Fusion

Paper Number: 133271

133271 - Comparison Analysis and Optimization Research of Open and Closed Air Brayton Cycle 

Abstract: 

Nuclear Energy is considered as a new energy source in the era of carbon peak and carbon neutrality. Microreactors have the significant impact on the strategy of energy safety. Due to the significant advantages of high security, compactness, high thermo-electric conversion efficiency, easy acquirement and supplement on working medium and so on, the air Brayton cycle system can serve as a reliable and dispatchable power conversion system of microreactor mobile nuclear power source in the remote islands or polar regions. Air Brayton cycle configuration adapted to different environments has a broad application prospect, which leads to comparison analysis and optimization work on open and closed air Brayton cycle systems.

In the present study, a 5 MW thermal heat pipe microreactor combining simple recuperating air Brayton cycle (SRC) energy conversion system is designed for mobile power source at remote sites. Using a system-component combined design method, the model establishment is carried out for both open and closed air Brayton cycle systems.  The influence of open and closed cycle parameters on the system performance index (cycle efficiency, exergy destruction rate of the components, system power density, and cost estimation) are investigated and compared, including compressor pressure ratio, recuperator efficiency, and so on. On this basis, a multi objective optimization is carried out by using Non-dominated Sorting Genetic Algorithms (NSGA-Ⅱ), in which cycle efficiency, system power density, mass and volume are considered. Finally, a comprehensive design-analysis-optimization strategy is established to adapt to different environmental assumptions. According to different requirements, relative coefficients of each objective can be listed, calculated and adjusted.

The results indicate that in the same power level, open and closed Brayton cycle systems reveal respective advantages.  Closed cycle system shows higher cycle efficiency and system power density than open cycle systems of the same configuration, because closed cycle remains higher pressure level than open cycle. Open cycle system has more compact structures due to the lack of cooler and indicate less estimated cost due to mature and advanced techniques of components, which demonstrate its advantages compared to the closed cycle system.

Under the multi-objective optimization by using two decision methods, the comprehensive optimization results of the 5 MW thermal power systems are calculated. With maximum cycle efficiency set as the most important attribute, the optimal design scheme of closed cycle system shows a cycle efficiency of ~28 %. With minimum volume as the most important attribute, open cycle system has a volume of ~6.2 m³, along with a power density of ~170 kW/m³.

Presenting Author: Meihui Song Xi'an Jiaotong University

Presenting Author Biography: Song Meihui is currently working toward the M.S. degree in Energy and Power with the State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, China. Her research interests focus on the new energy conversion system optimization and thermo-economic analysis.
She received the B.S. degree in Energy and Power Engineering from Xi'an Jiaotong University, Xi'an, China, in 2022.

Authors:

Meihui Song Xi'an Jiaotong University
Yuyang Leng Xi'an Jiaotong University
Yiran Qian Xi'an Jiaotong University
Weixiong Chen Xi'an Jiaotong University
Yi Yang China Institute of Atomic Energy
Junjie Yan Xi'an Jiaotong University