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Python implementation of international-standard IAPWS-IF97

Project description

Python implementation of international-standard IAPWS-IF97 steam tables


  • python 2x;3x, compatible with both versions
  • Numpy-scipy: library with mathematic and scientific tools


In debian you can find in oficial repositories in testing and sid. In stable you can install using pip:

pip install iapws

In other SO you can download from its webpage in pypi and unzipped in python folder dist-packages.


Class to model a state for liquid water or steam with the Industrial Formulation IAPWS-IF97

Incoming properties:

  • T, Temperature, K
  • P, Pressure, MPa
  • h, Specific enthalpy, kJ/kg
  • s, Specific entropy, kJ/kg·K
  • x, Quality, [-]

Definitions options:

  • T, P (Not valid for two-phases region)
  • P, h
  • P, s
  • h, s
  • T, x (Only for two-phases region)
  • P, x (Only for two-phases region)


  • P, Pressure, MPa
  • T, Temperature, K
  • g, Specific Gibbs free energy, kJ/kg
  • a, Specific Helmholtz free energy, kJ/kg
  • v, Specific volume, m³/kg
  • rho, Density, kg/m³
  • x, quality, [-]
  • h, Specific enthalpy, kJ/kg
  • u, Specific internal energy, kJ/kg
  • s, Specific entropy, kJ/kg·K
  • cp, Specific isobaric heat capacity, kJ/kg·K
  • cv, Specific isochoric heat capacity, kJ/kg·K
  • Z, Compression factor. [-]
  • gamma, Isoentropic exponent, [-]
  • alfav, Isobaric cubic expansion coefficient, 1/K
  • kt, Isothermal compressibility, 1/MPa
  • alfap, Relative pressure coefficient, 1/K
  • betap, Isothermal stress coefficient, kg/m³
  • joule, Joule-Thomson coefficient, K/MPa
  • deltat, Isothermal throttling coefficient, kJ/kg·MPa
  • region, Region
  • v0, Ideal specific volume, m³/kg
  • u0, Ideal specific internal energy, kJ/kg
  • h0, Ideal specific enthalpy, kJ/kg
  • s0, Ideal specific entropy, kJ/kg·K
  • a0, Ideal specific Helmholtz free energy, kJ/kg
  • g0, Ideal specific Gibbs free energy, kJ/kg
  • cp0, Ideal specific isobaric heat capacity, kJ/kg·K
  • cv0, Ideal specific isochoric heat capacity, kJ/kg·K
  • w0, Ideal speed of sound, m/s
  • gamma0, Ideal isoentropic exponent [-]
  • w, Speed of sound, m/s
  • mu, Dynamic viscosity, Pa·s
  • nu, Kinematic viscosity, m²/s
  • k, Thermal conductivity, W/m·K
  • alfa, Thermal diffusivity, m²/s
  • sigma, Surface tension, N/m
  • epsilon, Dielectric constant, [-]
  • n, Refractive index, [-]
  • Prandt, Prandtl number, [-]
  • Tr, Reduced temperature, [-]
  • Pr, Reduced pressure, [-]


from iapws import IAPWS97
sat_steam=IAPWS97(P=1,x=1)                #saturated steam with known P
sat_liquid=IAPWS97(T=370, x=0)            #saturated liquid with known T
steam=IAPWS97(P=2.5, T=500)               #steam with known P and T
print(sat_steam.h, sat_liquid.h, steam.h) #calculated enthalpies

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Files for iapws, version 1.0.4
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