Design and optimization of a Tesla turbine for ORC applications

In recent years, small-micro power generation was appointed as one of the proper solutions to tackle the increasing energy consumption, while opening the way to distributed energy systems and micro grids. The most interesting solution for small-micro power generation is the ORC technology, however, it still needs further developments especially regarding the design of small and micro expanders. A possible solution for micro-expanders is the Tesla turbine, which is a viscous bladeless turbine. This concept was developed by Nikola Tesla at the beginning of the 20th century, but it went through a long period of indifference due to the run towards large size centralized power plants. Only recently it found a renewed appeal, as its features make it suitable for utilization in small and micro size systems, like ORC applications, where low cost components become very attractive for the exploitation of residual pressure drop. The present study develops a design procedure of a Tesla turbine for ORC applications. A throughout optimization method was performed by evaluating the losses of each component and by introducing an innovative rotor model. Three turbine configurations with different expander size were assessed, in order to show the performance potential of the Tesla turbine, which achieved 64% total-to-static efficiency when working with N-hexane fluid.