Development of a 200 kW ORC radial turbine for waste heat recovery

There has recently been a growing interest in sustainable energy converters. One such technology is the organic Rankine cycle, which uses conventional turbine technology with a low temperature waste heat source. A 200 kW organic Rankine cycle system was designed for waste heat recovery application using R245fa as a working fluid. A radial type turbine with 15,000 rpm was employed to generate more than 200 kW with an expansion ratio of 9. Since R245fa has Ma = 1 at low velocity of the working fluid (about 1/3 of air sound of speed) at about 100°C, it reaches supersonic flow conditions easily with small pressure expansion. To avoid supersonic flow conditions in the turbine, the expansion ratio was evenly divided and applied to two turbine stages. Two radial type rotors were placed in the back-to-back layout in a single shaft. The inlet temperature of the turbine was about 124°C, and the inlet pressure was about 2 MPa. The designed turbine was fully tested in the 200 kW ORC system using the design conditions. It succeeded in generating more than 200 kW with R245fa. The performance of the turbine was validated with the experimental results and CFD analysis. Herein, the design procedure and performance evaluation of the ORC turbine was described using R245fa.