Instrumentation & Automation

Windows ⁄ Android

IAPWS-IF97

Calculation of the thermodynamic properties of steam and water is widely used in metrology. For calculating the primary devices for flow rate measurement, for example. At present, there are two main methods, two standards of the organization of the **IAPWS** (International Organization of Water and Steam Properties) - **IAPWS-95** and **IAPWS-97**.

The **IAPWS-95** has been released earlier. It is recommended for scientific calculations. In Russia, the analogue is **GSSSD 187-99**. The main disadvantage was the slow algorithm of computer calculations. Therefore, soon appeared a faster industrial standard of **IAPWS-97**, used in automated control systems. The difference in the calculations is small, but still exists.

In the **Instrumentation & Automation** application the **IAPWS-IF97** stanard is used. The input and calculated parameters are listed in the table below:

Calculated parameters | Pairs of input parameters:p - absolute pressureT - temperatureh - specific enthalpys - specific entropy | ||||

v | specific volume | p,T | p,h | p,s | h,s |

ρ | density | + | + | + | + |

s | specific entropy | + | + | + | + |

h | specific enthalpy | + | + | + | + |

u | specific internal energy | + | + | + | + |

g | specific Gibbs free energy | + | - | - | - |

Cp | specific isobaric heat capacity | + | + | + | + |

Cv | specific isochoric heat capacity | + | + | + | + |

Kt | isothermal compressibility | + | + | + | + |

λ | thermal conductivity | + | + | + | + |

k | thermal diffusivity | + | + | + | + |

η | dynamic viscosity | + | + | + | + |

ν | kinematic viscosity | + | + | + | + |

w | speed of sound | + | + | + | + |

αv | isobaric cubic expansion coefficient | + | + | + | + |

Pr | Prandtl number | + | + | + | + |

ε | dielectric constant | + | + | + | + |