OPTIMIZATION AND THERMAL ANALYSIS OF SUPERCRITICAL CARBON DIOXIDE BRAYTON CYCLE SYSTEM WITH ORGANIC RANKINE CYCLE

摘要: A supercritical carbon dioxide (S-CO2) Brayton cycle is recognized as the very promising heat-to-power technology. Compared with the traditional Rankine cycle, the supercritical carbon dioxide Brayton cycle has great advantages in cycle efficiency and equipment size due to the special physical properties of carbon dioxide near the critical point (31.1℃, 7.39 MPa). In recent years, it has received extensive attention in the fields of solar energy, nuclear energy, and waste heat utilization. Most of the current studies focus on the steady-state thermodynamic calculation and system layout design of the circulation system. However, a large space is still left for recompression S-CO 2 power cycle to improve its capability with regard to waste heat extraction and power output. Therefore, a lot of research work still needs to be done to optimize the system characteristics.The novelty of this work is the development of a new type of S-CO 2 power cycle with recompression cycle aimed at thoroughly and efficiently reusing the waste heat. The S-CO 2Brayton cycle system model is established using Aspen HYSYS software to analyze the performance of the cycle system. The model aims to study the effects of turbine inlet temperature, inlet pressure, condenser outlet temperature and compressor split coefficient on cycle thermal efficiency. The influence of the compressor outlet pressure and the turbine inlet temperature on the recombination Brayton cycle efficiency is significant. Main compressor split coefficient optimum value between 0.3-0.5. Moreover, Organic Rankine Cycle can increase the cycle thermal efficiency by 2-6%, compared to other cycles.