A simple method of finding new dry and isentropic working fluids for organic Rankine cycle

Gábor Györke, Axel Groniewsky, A. Imre

Research output: Contribution to journalArticle

5 Citations (Scopus)


One of the most crucial challenges of sustainable development is the use of low-temperature heat sources (60–200 C), such as thermal solar, geothermal, biomass, or waste heat, for electricity production. Since conventional water-based thermodynamic cycles are not suitable in this temperature range or at least operate with very low efficiency, other working fluids need to be applied. Organic Rankine Cycle (ORC) uses organic working fluids, which results in higher thermal efficiency for low-temperature heat sources. Traditionally, new working fluids are found using a trial-and-error procedure through experience among chemically similar materials. This approach, however, carries a high risk of excluding the ideal working fluid. Therefore, a new method and a simple rule of thumb—based on a correlation related to molar isochoric specific heat capacity of saturated vapor states—were developed. With the application of this thumb rule, novel isentropic and dry working fluids can be found applicable for given low-temperature heat sources. Additionally, the importance of molar quantities—usually ignored by energy engineers—was demonstrated.

Original languageEnglish
Article number480
Issue number3
Publication statusPublished - Feb 1 2019



  • Characteristic points
  • Droplet formation
  • Isentropic expansion
  • Isochoric heat capacity
  • Low-temperature heat sources
  • Molar quantities
  • ORC
  • Saturated vapor curve
  • T–s diagram

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Energy (miscellaneous)
  • Control and Optimization
  • Electrical and Electronic Engineering

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