A modified recompression S–CO2 Brayton cycle and its thermodynamic optimization

Abstract

A modified recompression S–CO2 Brayton cycle (RCSCBC) that combines advantages of the preheated S–CO2 Brayton cycle (PSCBC) is proposed to recovery the gas turbine waste heat. The modified RCSCBC cycle model considers finite temperature difference heat transfer between heat reservoir and working fluid, irreversible compression, irreversible expansion and other irreversibility losses. It is established by using finite time thermodynamics. Influences of various parameters on net power output (NPO) and thermal efficiency (TEF) of the cycle are analyzed. Performances of the modified RCSCBC are compared with those of the unmodified RCSCBC and the PSCBC. Performance optimizations are performed by optimizing diversion coefficients and heat conductance distributions among heat exchanges. The results show that the first diversion coefficient is the main factor affecting TEF, and there are optimal first diversion coefficient and pressure ratio to maximize the cycle TEF; the second diversion coefficient is the main factor affecting the NPO, and there is an optimal second diversion coefficient to maximize the NPO. Compared with unmodified RCSCBC, NPO of the modified RCSCBC can be increased by 14.34%, and TEF can be increased by 10.89%. Compared with PSCBC, NPO can be increased by 14.20%, and TEF can be increased by 16.60%.