Thermodynamic and exergy analysis of a S-CO2 Brayton cycle with various of cooling modes

Abstract

The thermal performance of S-CO2 Brayton cycle is deeply affected by the cooling mode as well as the meteorological and hydrologic conditions. We proposed the three different cooling modes, wet cooling system (WCS), dry cooling system (DCS) and hybrid cooling system (HCS), to the S-CO2 Brayton cycle, and its thermodynamic model was established adopting Ebsilon code. From the viewpoints of both energy and exergy, the efficiencies of cycles with WCS, DCS and HCS as well as the exergy loss distribution of component were analyzed, under full and partial load conditions. Then the influences of changeable meteorological parameters on the cycle performance and the corresponding thermodynamic parameters were studied. Results show the generation efficiency of cycle with DCS is highest, followed by that of cycle with HCS and WCS, and the corresponding supply efficiency of cycle with the three cooling modes are in reverse order. The thermal performance of S-CO2 Brayton cycle gradually deteriorates, as the ambient temperature increases (WCS, HCS, and DCS) or relative humidity decreases (WCS and HCS). HCS shows excellent water saving capacity (variation range of water saving ratio is 59.08%~95.56%), and its water saving effect is more obvious, as ambient temperature decreases and relative humidity increases. Meanwhile, HCS brings equivalent cycle thermal efficiency to WCS, which is recommended for the S-CO2 Brayton cycle in the water arid regions. The present research may lay a foundation for the water cooling system design and the whole cycle operation optimization.