Multi-component numerical investigation of a micro organic rankine cycle

Organic Rankine Cycles are frequently adopted for waste heat recovery applications from industrial processes. Micro-ORCs are characterized by low-grade heat sources (temperatures below 150 °C) with non-stationary operating conditions and small output power. ORC designers need to understand the system dynamics to perform the most efficient choice of components and working fluid. Furthermore, the analysis of off-design conditions can contribute tuning control strategies capable to deal with this variability. The authors propose a three-dimensional approach based on Computational Fluid Dynamics (CFD) for the study of the dynamics of ORCs. The simulation of a scroll expander coupled with plate heat exchangers has allowed the investigation of the dynamic behaviour of the two components. This demonstration shows the potentiality of this approach, investigating component mutual interaction, off-design conditions and the system's transient behaviour. The analysis is performed with an open-source CFD tool showing the importance of fully integrated 3D analyses.