**Ettore Fadiga \*, Nicola Casari, Alessio Suman and Michele Pinelli**

Department of Engineering (DE), University of Ferrara, 44122 Ferrara, Italy; nicola.casari@unife.it (N.C.); alessio.suman@unife.it (A.S.); michele.pinelli@unife.it (M.P.)

**\*** Correspondence: ettore.fadiga@unife.it; Tel.: +39-0532-974964

Received: 31 December 2019; Accepted: 29 January 2020; Published: 4 February 2020

**Abstract:** The spread of the organic rankine cycle applications has driven researchers and companies to focus on the improvement of their performance. In small to medium-sized plants, the expander is the component that has typically attracted the most attention. One of the most used types of machine in this scenario is the scroll. Among the other methods, numerical analyses have been increasingly exploited for the investigation of the machine's behaviour. Nonetheless, there are major challenges for the successful application of computational fluid dynamics (CFD) to scrolls. Specifically, the dynamic mesh treatment required to capture the movement of working chambers and the nature of the expanding fluids require special care. In this work, a mesh generator for scroll machines is presented. Given few inputs, the software described provides the mesh and the nodal positions required for the evolution of the motion in a predefined mesh motion approach. The mesh generator is developed ad hoc for the coupling with the open-source CFD suite OpenFOAM. A full analysis is then carried out on a reverse-engineered commercial machine, including the refrigerant properties calculations via CoolProp. It is demonstrated that the proposed methodology allows for a fast simulation and achieves a good agreement with respect to former analyses.

**Keywords:** scroll; opensource CFD; OpenFOAM; CoolFOAM; WOM; positive displacement machine; expander; ORC
