Increased power production through enhancements to the Organic Flash Cycle (OFC)

Tony Ho, Samuel S. Mao, Ralph Greif

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


The previously proposed Organic Flash Cycle (OFC) was shown to potentially improve power generation from finite thermal energy reservoirs. The OFC's primary advantage was improved temperature matching to the energy reservoir, thereby reducing exergy destruction and losses during energy transfer to the cycle working fluid. This advantage was negated though by irreversibilities introduced by flash evaporation. The present study proposes several design enhancements to the OFC. A theoretical analysis is conducted using the BACKONE, Span-Wagner, and REFPROP equations of state and ten aromatic hydrocarbon and siloxane working fluids previously suggested are reexamined. A comparison and discussion of the different improvements are also presented. Results showed that by splitting the expansion process into two steps and combining the liquid stream from flash evaporation in a secondary expansion stage, utilization efficiency gains of 10% above the optimized basic Organic Rankine Cycle (ORC) are achievable. The greatest efficiency gains were observed when combining this modification and replacing the flash evaporation throttling valve with a two-phase expander. Results showed that proposed enhancements had the greatest effect using aromatic hydrocarbon working fluids, increasing the utilization efficiency by 5%-20% over the optimized ORC; whereas for siloxanes, the improvement was limited to 2%-4%.

Original languageBritish English
Pages (from-to)686-695
Number of pages10
Issue number1
StatePublished - Sep 2012


  • Exergy analysis
  • Organic Rankine Cycle (ORC)
  • Solar thermal
  • Two-phase expander
  • Waste heat


Dive into the research topics of 'Increased power production through enhancements to the Organic Flash Cycle (OFC)'. Together they form a unique fingerprint.

Cite this