ABSTRACT
This chapter includes a detailed discussion on the various substances that can be potentially used as working fluids for organic Rankine cycle (ORC) applications. In the first part of the chapter, an overview of working fluids commonly considered in ORCs is included. Furthermore, the main principles guiding the selection of the most appropriate ones are 378presented, such as their toxicity, safety, compliance with environmental regulations and legislation, and technical feasibility. These parameters are quite often neglected, but are in fact very important, since they can lead to the exclusion of working fluids of superior thermodynamic performance. In the second part, a detailed thermodynamic investigation of some promising working fluids is carried out based on energy and exergy analyses, along with the evaluation of some additional technical parameters. Apart from the thermodynamic assessment, an investigation into the heat transfer performance under on- and off-design conditions of some fluids is performed. The purpose of this chapter is twofold; on one hand, it aims to introduce some of the most important concerns governing fluid selection in ORCs; on the other hand, it aims to highlight some of the most promising fluid candidates according to currently standard criteria.
