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Turbo-Expander Calculations

API 617 / GPSA Standards

Turboexpander Performance Calculator
Calculates turboexpander performance per GPSA Section 13 and API 617: power recovery, outlet temperature, and refrigeration duty. Compares expander vs. JT valve cooling for NGL recovery plant design.

Process Conditions

MMscfd
psia
psia
°F

Gas Properties

Air=1
-

Expander Performance

%
%
%

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About This Calculator

Calculates turboexpander performance for NGL recovery and energy recovery per GPSA Section 13 and API 617.

Key Features:

  • Power Output: Shaft and generator power (kW/HP)
  • Temperature: Polytropic outlet vs. isentropic ideal
  • JT Comparison: Expander benefit over throttling valve
  • Real Gas: Z-factor correction (DAK correlation)

Typical Applications:

  • NGL recovery plants (C2+ extraction)
  • Cryogenic gas processing
  • Pressure letdown with power recovery
  • LNG mixed refrigerant cycles

Design Guidelines:

  • Expansion ratio: 2.5:1 to 4:1 per stage
  • Polytropic efficiency: 80-88% typical
  • Mechanical efficiency: 97-99%

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