Advanced exergoeconomic and exergoenvironmental decision-oriented comparison of an ORC-VCR system: A comparative study of aromatic fluids under multi-fuel conditions

This study presents an integrated thermodynamic, advanced exergy, exergoeconomic, and exergoenvironmental assessment of an Organic Rankine Cycle – Vapor Compression Refrigeration (ORC – VCR) cogeneration system driven by the waste heat of a variable-compression-ratio multi-fuel engine. Three high – critical-temperature aromatic working fluids – O-xylene, M-xylene, and ethylbenzene – are investigated under diesel, gasoline, and biofuel operation to capture realistic variations in exhaust temperature and thermal availability. Advanced exergy analysis is employed to decompose component-level irreversibilities into avoidable/unavoidable and endogenous/exogenous parts, enabling identification of realistic improvement potential. To support integrated and transparent comparison, two normalized composite performance metrics – the Hybrid Performance Index (HPI) and the exergoeconomic – exergoenvironmental index (E3) – are formulated to couple thermodynamic efficiency with economic and environmental considerations in a dimensionless framework. The turbine and high-temperature heat exchanger are identified as dominant contributors to exergy destruction, accounting for 52–61% of total system irreversibility, with a substantial avoidable fraction. Comparative evaluation across fuel – fluid combinations indicates that O-xylene offers superior thermodynamic and hybrid performance, diesel – O-xylene emerges as the most favorable thermoeconomic pairing, and biofuel – M-xylene exhibits improved exergoenvironmental behavior. Sensitivity and uncertainty analyses confirm the robustness of the observed performance rankings. Overall, the study provides a structured, decision-oriented framework for comparative evaluation and prioritization of fuel – fluid combinations in waste-heat-driven ORC – VCR systems, rather than a formal mathematical optimization.