Energetic and Exergetic Analysis of a Basic and Regenerative Organic Rankine Cycle for Waste Heat Recovery System

Organic Rankine cycles (ORCs) are widely used to recover waste heat at high, medium, and low-temperature grades, depending on the availability of different energy resources such as geothermal, solar, and industrial waste heat. The selection of working fluids, according to the appropriate turbine inlet pressure and temperature, has a significant influence on the performance of both basic and regenerative ORC systems. For high-temperature heat sources, siloxanes are suitable working fluids for ORC systems. In the present study, two organic working fluids, namely, octamethyltrisiloxane (MDM) and Decamethyltetrasiloxane (MD2M) are evaluated in both basic and regenerative ORC systems in terms of energy and exergetic efficiency. The results show that MDM/MD2M improves the energy efficiency of the regenerative ORC system by 33% and 37.5%, respectively, compared to that of the basic ORC system, which sees improvements of 31% and 33.5%, respectively, at 14 bars.