Simultaneous Analysis of Supercritical Carbon Dioxide Power Cycle Coupling Zeotropic Organic Rankine Cycle with Composition-Adjustment and Dual-Pressure Evaporation

A novel cycle is established about the supercritical carbon dioxide power cycle (S-CO2) and the zeotropic organic Rankine cycle (ORC). The thermal efficiency of S-CO2 is superior to the steam Rankine cycle. However, the waste heat released from the expander is not well utilized. The zeotropic ORC with dual-pressure evaporation is considered to be one of the most promising cycles for recovering waste heat. Dual-pressure evaporation of ORC can improve the phase change heat transfer matching in the evaporation section, thus improving the energy conversion efficiency. If the composition of the zeotropic mixture can be adjusted during the dual-pressure evaporation process, the system power performance can be further improved. The supercritical carbon dioxide power cycle coupling the zeotropic organic Rankine cycle with composition adjustment and dual-pressure evaporation (S-CO2/ORC) is proposed for energy utilization efficiency. The influence of different working fluids and exergy destruction analysis is carried out for S-CO2/ORC. The results show that the net power output of the system is the largest, which is 359.79 kW, when R245fa-R236ea is used as the working fluid for the ORC. The analysis of the exergy destruction of S-CO2/ORC using R245fa-R236ea shows that the S-CO2 system accounted for the largest exergy destructions.