Turbine design for organic Rankine cycle

Organic Rankine Cycle (ORC) is one of the systems used to generate power from the waste or low-grade heat sources. The turbines are the most important system unit of ORC since it directly determines the overall system efficiency. In this study, the designs of regenerative flow turbines (RFT) for small-scaled ORC systems through the computational fluid dynamics (CFD) analysis method. Firstly, a validation study was conducted to determine the best available turbulence model on the conventional RFT. R601 (n-pentane) is used in the analysis for the low and high temperatures, different pressures and different rotational speeds. Temperature scales was selected between 363K and 550K considering the residential applications. According to the temperature scales, the outlet pressures were evaluated between 0.9-1.2 MPa for the high temperature applications, and 0.05-0.3 MPa for the low temperature applications. Turbine speeds were selected as 1500 rpm and 3000 rpm in accordance to 50 Hz applications of the national networks. The analyses were conducted for the mass rates ranging between 0.5-1.0 kg/s for the high temperature applications and 0.1-0.25 kg/s for the low temperature applications. According to analysis results of the new designed RFT, it was available to increase the efficiency by 18.59% in comparison to the conventional RFT for the low temperature applications, whereas it is about 11.29% for the high temperature applications. These means an isentropic efficiency increase about 6.54 points and 2.26 points for the low and high temperature applications, respectively.