Comparison Between Centrifugal and Inward Radial Turbines for Organic Rankine Cycle Plants

Organic Rankine Cycle (ORC) systems have received growing interest due to their potential applications in renewable energy power plants (solar, geothermal, biomass) and waste heat recovery applications. Despite being a consolidated technology, they usually suffer from low plant efficiency connected with their thermodynamic constraints (low/medium temperature of the available heat source). Therefore, to not penalize their performance even more, particular attention has to be paid to a good design of key components like the turbine. Most of the turbines applied are axial or inward-flow radial machines derived from other applications. This paper compares a two-stage inward and an innovative multi-stage centrifugal turbomachine designed for the same case study. Both machines are designed and analyzed by using 3D CFD steady state simulations. Performance and main pros and cons are highlighted for both machines working with pentane.