Energy, exergy and economic analysis and optimization of various modified organic flash cycle configurations for enhanced waste heat recovery performance

This study presents a comprehensive thermodynamic investigation based on energy, exergy, and economic (3 E) analysis of eight Organic Flash Cycle (OFC) configurations for waste heat recovery. The modified cycles were modeled in MATLAB with thermophysical properties obtained from REFPROP 9.0. The proposed configurations integrate advanced components such as two-phase expanders and ejectors to minimize throttling losses and improve overall system performance. Unlike the dual-ejector systems reported by Chen et al. (2019), one of the proposed configurations, namely Two-phase expander and single ejector OFC-II (TPSEOFC-II) eliminates the secondary flash separator, resulting in a 21.5 % reduction in total costs and a 37.25 % improvement in exergy efficiency. Multi-objective optimization using the Multi-Objective Grey Wolf Optimizer was employed to simultaneously maximize energy efficiency and exergy efficiency while minimizing the levelized cost of energy (LCOE). The TPSEOFC-II configuration achieved a net power output of 363.19 kW, an energy efficiency of 13.24 %, an exergy efficiency of 75.94 %, and the lowest LCOE of 0.0159 $/kWh, representing substantial improvements over the baseline OFC-I and OFC-II systems. These results highlight the potential of advanced OFC designs for cost-effective and sustainable waste heat recovery applications.