Taguchi Optimization of Triple-Tube Organic Rankine Cycle Evaporator for Enhanced Combined Heat and Power System Efficiency With Diverse Refrigerants

Abstract Evaluations were conducted using the Taguchi method to optimize a novel triple-tube evaporator-based organic Rankine cycle combined heat and power (ORC-CHP) system. The system replaces traditional ORC evaporators with a triple-tube configuration, featuring hot fluids in the inner annular, normal fluid in the outer annular, and refrigerants R152a, R600a, R32, and isopentane in the inner tube. The effects of net work done, total irreversibility, and exergetic efficiency on the pinch point temperature difference (PPTD), evaporator, and condenser temperature were analyzed using the Taguchi method in minitab 16 software. Results demonstrated the superior performance of R600a with the ORC-CHP system achieving optimal energetic efficiency and performance index (PI) at higher evaporator temperatures. Energetic efficiency is decreased by 9.8%, 10%, 10.6%, and 9.5% for R152a, R600a, R32, and isopentane, respectively, across a PPTD range of 3–10 °C, while the maximum exergetic efficiency of 49.59% was observed for R32 at 45 °C evaporator temperature. The PI value is increased linearly by 3%, 2.98%, 2.8%, and 3.12% for R152a, R32, R600a, and isopentane, respectively, across an evaporative temperature range of 45–65 °C. Taguchi's optimization revealed that evaporator temperature significantly enhances the system performance, with R600a emerging as the most favorable refrigerant. Its scalable design allows for customization, making it adaptable for both small- and large-scale applications. A simple fabrication of the system reduces the maintenance complexity and cost compared to more intricate heat exchanger designs. This study bridges the technological gap in ORC-CHP systems by demonstrating the advantages of a triple-tube evaporator, offering improved efficiency and performance over traditional techniques and contributing to developing advanced low-grade heat recovery systems.