Parametric analysis and thermodynamic optimization of organic rankine cycle for low grade waste heat recovery

Abstract

The system consists of a low temperature heat source coupled to an organic rankine cycle (ORC) system. The working fluids used are R245fa, R123, isobutane and R134a. The ORC model is developed in EES by adopting zero- dimensional energy and mass balance approach. A parametric investigation has been carried out to study the impact of few thermodynamic parameters on the performance of the system. Genetic algorithm optimization technique is adopted to find the optimal parameters at which the system can be operated with maximum exergy efficiency. Maximum exergy efficiency of 45.53% was obtained with R123 followed by R245fa (44.98%), isobutane (42.89%) and R134a (41.91%). The optimal turbine inlet pressure for R245fa, R123, isobutane and R134a was 6.07 bar, 3.66 bar, 10.36 bar and 19.94 bar, respectively. Sensitivity analysis showed that the turbine inlet pressure has the highest sensitive degree with respect to all performance indicators when compared with other system parameters. Variation in pinch point temperature difference showed no impact on thermal efficiency. R245fa and R123 are better suited for low temperature ORC systems compared to R134a and isobutane due to their efficient system performance and low operating temperatures and pressures. 2019 - Kalpana Corporation.