Thermodynamic assessment of a novel self-condensing sCO2 recompression system with vortex tube

Low temperature heat sink is required to condense the supercritical CO2 (sCO(2)) owing to its low critical temperature, this limits the sCO(2) power system application. In this paper, a self-condensing sCO(2) recompression system with vortex tube is proposed, which achieves the CO2 condensation without the low temperature heat sink and recompression near the critical point in order to improve the system energy and exergy efficiencies. The system performance is investigated from the first and second laws of thermodynamics point of view, and parametric study is conducted to clarify the influences of key design and operation parameters, including the mass flow rate split ratio, the minimum and maximum pressures and temperatures. In a base case scenario with 100 kW power output, the system energy and exergy efficiencies reach 35.50 % and 58.21 % respectively. In the optimum operating condition, the system has the ability to provide 129.80 kW power output with the maximum energy efficiency of 41.90 % and exergy efficiency of 60.89 %.