Session: 30-05 Solar Thermal Systems

Paper Number: 121685

121685 - Performance Evaluation of a Direct Air-Cooled Supercritical Recompression Brayton Cycle Using CO2/n-Butane As the Working Fluid Operating Under Off-Design Conditions 

The use of efficient and compact direct air-cooled supercritical Brayton cycle employing the CO₂-based binary mixture has great application potential in solar tower thermal power plants. The thermal stability of the working fluid operating at high temperatures greatly affects the thermodynamic performance of the power cycle. The purpose of this study is to establish the off-design model of a direct air-cooled supercritical recompression Brayton cycle based on CO₂/n-butane mixture and obtain the effect of thermal decomposition of the working fluid. The component models of the 10MWe direct air-cooled supercritical recompression Brayton cycle are developed. Under off-design conditions, i.e., ambient air temperature and normalized heat input, cycle efficiency and key parameters of the power cycle are evaluated. The ReaxFF MD method is employed to perform pyrolysis processes of the CO₂/n-butane mixture for the thermal decomposition data of the CO₂/n-butane. The results show that the rated thermal efficiency decreases by 4.1% when the ambient temperature increases from the designed 35 ℃ to 50 ℃. When the normalized heat input is reduced to 0.3, the thermal efficiency decreases by nearly 12.5%. In addition, the thermal efficiency decreases by 35% and 55% when the thermal decomposition rate of CO₂/n-butane working fluid is 50% and 100%, respectively.

Presenting Author: Xurong Wang Henan University of Urban Construction

Presenting Author Biography: Xurong Wang received the PhD degree in Power Engineering and Engineering Thermophysics at Xi'an Jiaotong University in 2018. He currently works at Henan University of Urban Construction. His research interest includes supercritical CO2 Brayton cycle and low-grade waste heat recovery technologies.

Authors:

Xurong Wang Henan University of Urban Construction
Longwei Zhang Shandong University
Jianhui Qi Shandong University
Xiaowei Fan Henan University of Urban Construction
Yiping Dai Xi’an Jiaotong University