High-Throughput Screening of ORC Fluids for Mobile Applications

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High-Throughput Screening of ORC Fluids for Mobile Applications

Preißinger, Markus / Schwöbel, Johannes / Klamt, Andreas / Brüggemann, Dieter

Abstract Although huge effort has been invested in research and development of Organic Rankine Cycle (ORC) systems for mobile applications, it was not possible so far to identify a working fluid which covers nearly all of the requirements defined by OEMs and component suppliers. Therefore, the intention of this work was the identification of a so-called “superfluid” by screening the complete chemical space of more than 72 million chemical substances given by the PubChem© database. For this purpose, a fast simulation tool (DetailSimORC) was programmed in Matlab®. The thermodynamic properties were gained by the COSMOtherm software with a combination of the COSMO-RS theory and a cubic equation of state. The subsequent evaluation was based on a scoring system taking into account constructional aspects (e.g. minimum pressure level), safety issues (e.g. flammability) and regulatory requirements (e.g. ozone depletion potential, ODP) in addition to the thermodynamic performance. The results revealed that a conflict occurs between optimal thermodynamic performance and safety issues. Fluids showing a high net power output and low ODP are often highly flammable, whereas well-performing non-flammable working fluids have drawbacks concerning environmental and toxico-logical issues. Keeping these conflicting priorities in mind, it is possible to select a set of diverse best-ranked fluids for further investigation: the alcohol ethanol, the linear siloxane hexamethyldisiloxane, as well as the refrigerant R-152 (1,2-difluoroethane).