Investigation of Organic Rankine Cycle Performance with Variable Mixture Composition

The present study deals with a comprehensive thermodynamic modeling of a renewable energy-based organic Rankine cycle (ORC). In this regard, two different cases are chosen to investigate the effect of mixture composition on the cycle performance in terms of exergy efficiency. While one cycle responses negatively to the mixture variation, another shows an increase in cycle performance and hence, efficiency. In addition, this study reveals that using a variable mixture composition can provide a wide range of working conditions for design purposes. The effects of working fluid composition on the turbine and pump works and exergy efficiency of the cycle are investigated, and the results are discussed as well. The exergy efficiency drops by about 0.002 in the first case, but increases by about 0.01 in the second case. It appears that temperature ratios can act like indicators of the cycle performance.