The Evaluation of Thermodynamics and Environmental Impact of Waste Heat Recovery System Using Alternative Refrigerants

¹ Department of Mechanical Engineering, Vocational School, Universitas Gadjah Mada, Jl. Yacaranda, Sekip Unit IV, Yogyakarta, Indonesia
² Department of Mechanical and Industrial Engineering, Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika No.2, Yogyakarta, Indonesia

^* Corresponding author: sugiyanto_t@ugm.ac.id

Abstract

Diesel engines play a critical role in numerous sectors due to their robustness and efficiency but contribute significantly to environmental pollution through exhaust emissions. These emissions contain substantial thermal energy, which, if not harnessed, exacerbates air quality issues and global climate change. The Organic Rankine Cycle (ORC) offers a promising solution for recovering this waste heat and converting it into mechanical or electrical power. This study conducts thermodynamic simulations using MATLAB to analyze ORC systems for diesel engine exhaust heat recovery, focusing on thermal efficiency, power generation potential, and environmental impact of different refrigerants, specifically R-141b, R-245fa, and R-123. Results indicate that ORC performance is significantly influenced by the refrigerant’s critical temperature. R-141b demonstrates the highest thermal efficiency at 13.13% with a heat source temperature of 120°C but also has the highest environmental impact, contributing 3,090 kgCO2 eq/year. In contrast, R-123 shows the lowest environmental impact at 231 kgCO2 eq/year for direct TEWI and 7.73 kgCO2 eq/year for indirect TEWI, with a slightly lower thermal efficiency of 12.73%. R-245fa, with the lowest efficiency at 12.14%, also has a substantial environmental impact. This research provides insights into optimizing energy recovery from diesel engine waste heat and advancing sustainable energy solutions.