Expander design procedures and selection criterion for small rated organic rankine cycle systems

The particular aspect of this work is the new approach to expander design procedure for small rated ORC. In fact, once all the calculation procedures have been defined, they have been implemented in Matlab code. This code, once the design process is complete, provides an indication of the optimal expander configuration to adopting to that specific system. For these reasons, this paper aims to analyze all the preliminary expanders' design procedures, both dynamic and volumetric. The reasons lie in the development of low-enthalpy heat recovery systems (systems that allow simultaneous production of electrical and thermal energy made available in the form of water at a temperature of 60-90°C), with the aim of optimizing any energy system. Within these energy systems, the expander is the main component, responsible for power generation. It is, therefore, necessary and useful to analyze in detail every expander configuration, highlighting the different features. For each component will be described the theory on which is based the choice and its design and a possible software implementation is supplied. Finally, a criterion for the choice of the optimal expander is proposed, based on some operational considerations and other construction and structural constraints, such as overall dimensions and weight, lubrication, MTBF, feasibility, reliability, and coupling with the electric generator