Analysis of a novel combined cooling and power system by integrating of supercritical CO2 Brayton cycle and transcritical ejector refrigeration cycle

• A novel combined cooling and power (CCP) system is proposed. • The effective efficiency of the CCP system is up to 0.42. • The heat exchanger has small exergy destruction because of good temperature match. • The CCP system is more stable and efficient than the conventional CCP system. • R1234ze is a good choice for a high thermal efficiency and low environment impact. This paper presents a novel combined cooling and power (CCP) system that integrates a supercritical CO 2 Brayton (sCO 2 ) cycle and a transcritical ejector refrigeration cycle. The two cycles are combined by a heat exchanger wherein heat is exchanged between CO 2 and the refrigerant at supercritical pressures to reduce exergy destruction and improve system performance. A thermodynamic model was established to simulate the CCP system based on energy and exergy balance equations. The transcritical ejector model was validated with experimental and literature data. The performance of the system was studied for different CO 2 mass flow rates, turbine inlet temperatures, turbine inlet pressures, turbine outlet pressures, and pump outlet pressures. The thermal, exergy, and effective efficiencies of the CCP system were compared with those of a combined cooling and power system (CCP_ab) that uses a single-effect absorption refrigeration cycle. The CCP system maximum thermal efficiencies of four refrigerants— R 32, R134a, R1234yf, and R1234ze—were obtained using a genetic algorithm. The results show that the major components that contribute in exergy destruction are internal heat exchanger, ejector, compressor and turbine, and the heat exchanger has small exergy destruction because of a good variable-temperature match between the supercritical pressure refrigerant and supercritical pressure CO 2 . The effective efficiency of the CCP system reaches 0.42 at turbine inlet temperature of 873.15 K. The CCP system is more stable and efficient than the CCP_ab system in varying conditions. The CCP system with R 32 has the highest thermal efficiency. R1234ze with relatively high thermal efficiency and low Global Warming Potential is a good choice in the future as it is environmentally friendly.