열침원의 온도 변화에 따른 초임계 이산화탄소 재압축 사이클의 탈설계 거동 평가

Abstract

Today, securing environmental friendly energy source became an important global issue. Such energy source can be developed by using a new resource or using the existing energy resource more efficiently. Recently substantial attention was given to the supercritical CO₂ power cycle which can transform the existing electricity production method. The supercritical CO₂ power cycle has advantages of small turbomachinery, simple system, and high thermal efficiency. However, due to non-linear properties’ variation near the critical point, the off-design performance prediction of the cycle still requires further research. Thus, the research team have analyzed the off-design behavior of the supercritical CO₂ cycle according to the temperature change of the heat sink. The target cycle in the study is a 100 MW scale supercritical CO₂ recompression Brayton cycle layout, and the off-design behavior was analyzed when the temperature of the heat sink increases from the design point of 32 °C to 50 °C. The system maximum pressure was assumed to be remained the same as the design point. In the analyzed temperature range, the system efficiency is calculated to decrease by 11.5%p from 44% to 32.5%, and the thermodynamic work of the cycle is expected to decrease by about 38MW, from 108 MW to 70 MW. In the process of changing the system minimum pressure during the analysis, necessity for new optimizations to meet the off-design operating condition was found. This suggests that optimizing the rpm of the turbomachinery and the overall system capacity to meet operating conditions will be an important research topic in the future.