A novel self-condensing transcritical CO2 power cycle with a vortex tube: Thermoeconomic assessment study and comparison

Abstract

The low critical temperature of carbon dioxide (CO2) requires low-temperature heat sinks for condensation, which limits the application of the transcritical carbon dioxide (tCO2) power cycle system. This paper proposes a novel self-condensing tCO2 power cycle system with a vortex tube, which uses the vortex tube to achieve CO2 condensation without an external low-temperature heat sink. Firstly, the detailed thermodynamic and economic models of the proposed tCO2 power cycle system are established and verified. Then, the effects of decision variables on the thermoeconomic performances of the system are studied through parametric analysis. Finally, the performances of the self-condensing tCO2 power cycle system and the simple regenerative supercritical carbon dioxide (sCO2) power cycle are optimized and compared by single-objective and multi-objective optimizations. The single-objective optimization results reveal that the optimal thermal efficiency, exergy efficiency, and the levelized cost of electricity of the self-condensing tCO2 power cycle system are 41.42%, 69.01%, and 0.0739 $/(kW·h), which are 3.06%pt (percentage point) higher, 3.89%pt higher and 3.90% lower than those of the simple regenerative sCO2 power cycle system. The multi-objective optimization results show that compared with the simple regenerative sCO2 power cycle system, the self-condensing tCO2 power cycle system improves the thermal and exergy efficiencies by 1.81%pt and 2.41%pt at the expense of 3.37% higher in the levelized cost of electricity. Exergy destruction analysis reveals that the high temperature recuperator has the largest exergy destruction, which should be improved first.