Off-design model of an ORC system for waste heat recovery of an internal combustion engine

Abstract

• ASPEN® HYSYS software, off-design cycle simulations were done to evaluate Organic Rankine Cycle performance; • Economic calculation, CEPCI based, evaluated the feasibility of plant implementation; • A technical and economic analysis for an Organic Rankine Cycle was performed. The exhaust gases of an ICE leave the equipment still with enough temperature to generate more electric power if a proper system is used for that purpose. Therefore, due to this scenario, in this work a study of an ORC system to recovery energy from the flow gases of a stationary diesel engine. The analyses are in three parts: (1) parametric analysis of an ORC system in on-design to determine the cycle's optimal operating point; (2) parametric analysis in off-design condition, to verify the behavior of power production and cycle efficiency when the heat source's flow and temperature are varied; (3) An economic analysis, a CEPCI based model was used. The system design was determined for a working fluid flow rate of 0.09 kg/s, evaporation and condensation pressure of 3,870 kPa and 25 kPa, respectively, and with exhaust gas at 420 °C and 0.1697 kg/s. For the off-design simulations, the evaporation pressure, the working fluid flow and the heat source inlet conditions were varied. A minimum, average, and maximum net power production of 8.56 kW, 15.59 kW, and 26.29 kW, respectively, was verified, while in the design condition it was 14.72 kW, there was also an average increase in exergy of 9.35%. The initial investment for the system's implementation is US$ 23,257.02 and the financial return and rate of return reach an average of 1.5 years and 90%, respectively. The study shows that the system increases the power plant's thermal efficiency and decreases fuel consumption as well as the emission of pollutant gases.