Performance analysis and optimization of a dual-pressure organic Rankine cycle system with dual vapor–liquid separators coupled with an ejector

• A novel dual-pressure organic Rankine cycle system with a coupled ejector is proposed. • Ejector operating parameters are analyzed for their impact on thermodynamic performance. • Parameter sensitivity of the ejector is investigated through coupling analysis. • The CRITIC–TOPSIS method is applied for multi-objective system evaluation. Driven by carbon-neutrality goals, efficient recovery of low-grade thermal energy has become increasingly important. This study develops a novel ejector-integrated dual-separator dual-pressure Organic Rankine Cycle (EJ-DS-DPORC), which couples ejector-based vapor upgrading with phase-quality control using dual separators. This configuration enhances fluid distribution and thermal matching between pressure stages, thereby addressing persistent issues in conventional ejector-assisted ORC systems, such as heat-source mismatch and uncontrolled vapor quality. A comprehensive thermodynamic model and multi-objective optimization are conducted considering net power, thermal efficiency, exergy efficiency, specific investment cost, and annual emission reduction. Under representative operating conditions (Rp ≈ 5.1, Er ≈ 0.84), the EJ-DS-DPORC achieves 342.9 kW net power, 13.4 % thermal efficiency, and 66.2 % exergy efficiency. Compared with the baseline DS-DPORC (312.4 kW, 12.7 %, 56.1 %), these correspond to improvements of 9.8 %, 1.7 %, and 10.1 %, along with a 4.8 % reduction in specific investment cost and a 10.6 % increase in annual greenhouse-gas reduction. The environmental benefit is evaluated under a life-cycle boundary that accounts for both electricity-generation displacement and embodied emissions of major system components. Overall, the EJ-DS-DPORC demonstrates notable energy, economic, and environmental advantages, highlighting its strong potential for high-efficiency recovery of low-grade heat. Nevertheless, the coordinated control of fluid distribution between the two pressure levels and the stable operation of the ejector introduce additional system complexity, implying that careful design of control strategies and operational safeguards is necessary for practical implementation.