Molecular Complexity of Working Fluids Dedicated to Organic Rankine Cycle (ORC)

Abstract

Organic Rankine Cycle (ORC) power plants are the most well-known and mature technology used to converting low and medium-temperature heat into electricity, especially from waste heat and renewable energy sources (including geothermal and solar thermal). Despite the level of development of ORC systems available on the market, there are still many aspects in the context of improving those units - constructing economically profitable low power unit, improving efficiency, selection an appropriate working fluid, etc. This paper analyzes 17 workings fluids dedicated to ORC system and discusses an existence of low stability region in their dense vapors and its influence on some peculiarities in behaviors of selected isentropic and dry fluids. The analysis shows relation between the retrograde phenomena in the flow of ORC fluids and mechanical and thermodynamic stability parameters.