Potential Application of CO2-Based Mixtures in the Combined Power and Cooling System for the Waste Heat Recovery

Abstract

To reduce the operating pressure and broaden the range of condensation temperature, it is proposed to mix CO2 with organic fluid to form a zeotropic mixture. However, how CO2-based mixtures perform in the combined power and cooling system is still an open question. Therefore, in this study, aiming at the newly proposed system for waste heat recovery, CO2/R600a and CO2/R601a mixtures are first employed to produce power and cooling. Based on the established models, the energy and exergy performances of combined system with CO2-based mixtures are analyzed. The effects of key parameters on system performances are investigated. On this basis, the performance optimization is conducted to maximize net work by using a genetic algorithm (GA), and the optimal system performance of mixtures and pure CO2 are compared. The results indicate that under the basic operating conditions, the net works of CO2/R600a (0.5/0.5) and CO2/R601a (0.5/0.5) are 2717.93 kW and 1145.98 kW, respectively. The optimal results indicate that among the considered working fluids, the highest specific net work is always obtained by CO2/R600a system. This study will be helpful to the development of combined power and cooling systems with CO2-based mixtures.