Mathematical modelling for positive displacement expanders

The expander of an organic Rankine cycle (ORC) influences the performance, investment cost, and control of the ORC system. In the past few years, there had been an increasing interest in the development of positive displacement expanders. The purpose of the present chapter is to provide detail insight into the principle of operation, kinematics and geometry and mathematical modelling approach for major technologies of displacement expanders. The chapter also provides an insight into the current development status of the positive displacement expander. The technical limitations and performance indicators are also discussed at the end of the chapter.