ORC Refrigerants at 300 psi: Temperature Limits, Efficiency, and Usage Notes

ORC Refrigerants at 300 psi: Temperature Limits, Efficiency, and Usage Notes

Note: the standard Infinity Turbine ORC systems are designed for 300 psi operation. If you want higher pressure, then consider our Supercritical CO2 systems.

Introduction

In Organic Rankine Cycle (ORC) systems, the thermodynamic properties of refrigerants determine efficiency, operating conditions, and overall system performance. By comparing refrigerants at a standard pressure of 300 psi (~20.7 bar), we can evaluate how temperature capability, efficiency, and practical use cases differ. This article lists common ORC refrigerants, their temperature at 300 psi, Carnot efficiencies at those temperatures, optimal condenser ranges, and regulatory notes.

R-245fa (Honeywell Genetron)

Temperature at 300 psi (20.7 bar): ~125 °C (257 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~25 percent

Condenser Temperature: Most effective around 30–35 °C (86–95 °F)

Notes: High global warming potential (GWP ~950). Facing phase-out in the EU under F-Gas Regulation.

R-1233zd(E) (Hydrofluoro-olefin, HFO)

Temperature at 300 psi (20.7 bar): ~155 °C (311 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~29 percent

Condenser Temperature: Effective in the 25–35 °C (77–95 °F) range

Notes: Very low GWP (~1). No near-term sunset dates. Widely promoted as a sustainable replacement for R-245fa.

R-123 (HCFC, historical use)

Temperature at 300 psi (20.7 bar): ~110 °C (230 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~23 percent

Condenser Temperature: Best around 25–30 °C (77–86 °F)

Notes: Phased out globally under the Montreal Protocol due to ozone depletion potential. Not viable for new ORC systems.

R-600 (n-Butane)

Temperature at 300 psi (20.7 bar): ~140 °C (284 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~27 percent

Condenser Temperature: Optimal near 25–30 °C (77–86 °F)

Notes: Low GWP but highly flammable. Regulatory and safety concerns limit adoption in many regions.

R-601 (Pentane)

Temperature at 300 psi (20.7 bar): ~160 °C (320 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~30 percent

Condenser Temperature: Performs best at 25–30 °C (77–86 °F)

Notes: Low GWP hydrocarbon with strong thermodynamic performance, but flammability is a concern.

R-152a

Temperature at 300 psi (20.7 bar): ~100 °C (212 °F)

Carnot Efficiency (vs 30 °C / 86 °F condenser): ~21 percent

Condenser Temperature: 25–30 °C (77–86 °F)

Notes: Moderate GWP (~124). Being phased down under F-Gas rules, but sometimes used as a substitute for higher-GWP fluids.

Summary Table at 300 psi

| Refrigerant | Temp at 300 psi (°C / °F) | Carnot Efficiency (%) | Best Condenser Temp (°C / °F) | Notes |

| --• | • | --• | -• | -• |

| R-245fa | 125 / 257 | 25 | 30–35 / 86–95 | High GWP, EU sunset |

| R-1233zd(E) | 155 / 311 | 29 | 25–35 / 77–95 | Low GWP HFO, no sunset |

| R-123 | 110 / 230 | 23 | 25–30 / 77–86 | HCFC, phased out |

| R-600 (Butane) | 140 / 284 | 27 | 25–30 / 77–86 | Low GWP, flammable |

| R-601 (Pentane) | 160 / 320 | 30 | 25–30 / 77–86 | Low GWP, flammable |

| R-152a | 100 / 212 | 21 | 25–30 / 77–86 | Moderate GWP, phasedown |

Conclusion

When standardized at 300 psi, ORC refrigerants show clear performance distinctions. Hydrofluoro-olefins like R-1233zd(E) provide both high thermal capability and regulatory acceptance. Hydrocarbons such as pentane and butane offer solid performance but pose flammability risks. Legacy fluids like R-123 and high-GWP HFCs like R-245fa are being phased out. Choosing the right refrigerant depends on balancing efficiency, condenser conditions, and regulatory compliance for the ORC application.

Note: Infinity systems are not designed for flammable working fluids

TEL: 1-608-238-6001 Email: greg@infinityturbine.com

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