Organic Rankine cycle performance evaluation and thermoeconomic assessment with various applications part I: Energy and exergy performance evaluation

Abstract

The utilization of low grade energy and renewable energy heat sources for power generation in organic Rankine cycle (ORC) system has received more attention in recent decades. In this study, working fluid candidates for various ORC applications based on the heat source temperature domains have been investigated for the thermal efficiency, exegry destruction rate and mass flow rate under different ORC configurations. The net power output from the ORC remains constant. The thermal efficiency increases as the condensing temperature diminishes, and decreases as the evaporating pressure recedes. As the condensing temperature and evaporating pressure are fixed, it can be found that as the critical temperature of the working fluid is increased, the thermal efficiency can be increased. As the heat source temperature scale increases, the operating evaporating pressure of the working fluids can be extended. The ORC with internal heat exchanger (IHX) has a higher thermal efficiency than the baseline ORC. The reheat ORC thermal efficiency is close to the baseline ORC. The regenerative ORC can achieve higher thermal efficiency than the baseline by reducing the addition of heat from the evaporator heat source. The performance of working fluid mass flow rate can reach their maximum in the low thermal efficiency region. The ORC with IHX and regenerative ORC have a lower value for exergy destruction as compared to baseline. Reheat ORC has a slightly higher exergy destruction rate. The evaporator is the largest contributor for the exergy destruction rate. In addition, the effect of IHX effectiveness, reheat pressure and regenerative intermediate pressure on system performance has been revealed and identified.