Thermodynamic and Exergy Analysis of an Isopentane-Based Organic Rankine Cycle for Waste Heat Recovery
DOI:
https://doi.org/10.70112/ajsat-2026.15.1.4342Keywords:
Organic Rankine Cycle, Isopentane, Exergy Analysis, Thermal Efficiency, Waste Heat Recovery, Renewable Energy, Low-Temperature Heat Sources, Second-Law Efficiency, Thermodynamic OptimizationAbstract
The growing need for renewable and sustainable energy technologies for efficient power production has led researchers to investigate various techniques that employ the use of low-temperature sources of energy to produce power. One of the efficient technologies that has proven to be very useful in generating power from low and medium temperature heat sources is the Organic Rankine Cycle. This paper explores the thermodynamics, exergy analysis, and economics of an ORC using Isopentane fluid. Analysis of the ORC performance is based on energy and exergy balance equations taking into consideration changes in condenser pressure, evaporator pressure, and superheating temperatures. Thermophysical properties and thermodynamics of the Isopentane cycle were determined using REFPROP software based on the environmental friendliness, safety, and thermodynamics considerations of Isopentane. Parameters that were considered include pump work, turbine work, heat added, heat rejected, thermal efficiency, exergy destruction, and second-law efficiency. Three optimization cases were investigated to improve cycle performance: decreasing condenser pressure to 0.15 MPa, increasing the superheating temperature to 455 K, and increasing evaporator pressure to 3.2 MPa. The results suggest that the thermal efficiency and second-law efficiency of the cycle are substantially enhanced by reducing the condenser pressure. At a condenser pressure of 0.15 MPa, 30 percent second-law efficiency and a maximal thermal efficiency of 16% were attained. Superheating increased the total exergy of the system, while higher evaporator pressure provided moderate improvements in efficiency. The study also demonstrates that Isopentane is a suitable working fluid because of its high specific heat capacity, favorable critical temperature, non-toxic nature, and environmentally friendly characteristics. In addition, a solar thermal collector and thermal storage system were integrated with the ORC system to enhance energy utilization and overall performance. Economic analysis showed that the system can generate approximately 460,080 kW annually with an estimated payback period of about five years. The results of this work show the capability of Isopentane-based ORC systems for efficient recovery of waste heat and sustainable power generation from renewable and low-temperature energy sources.
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