SEUIF97

This is the C implementation of the high-speed IAPWS-IF97 package SEUIF97. It is suitable for computation-intensive calculations，such as the simulation of non-stationary processes, on-line process monitoring and optimizations.

Through the high-speed library, IAPWS-IF97 results are generated with high accuracy and at speeds significantly faster than the repeated squaring method or the standard C library's math.pow()

SEUIF97 is also faster than approximate equations and other fast-calculation algorithms for water and steam properties.

Key Acceleration Methods

• Shortest Addition Chain Algorithm: Used for the rapid computation of integer powers via optimal multiplication sequences.
• Power Caching Strategy : Precomputes only distinct powers to avoid redundant calculations, directly retrieving them to speed up polynomial evaluation.
• Recurrence Method for Multi-Polynomial Evaluation: Computes a base polynomial, then utilizes derivative relationships to derive the rest via base scaling to maximize efficiency.

Please refer to The acceleration methods for more details on the algorithm.

The shared library

Building the shared library

You can build the library using either make or cmake:

• make

make

• cmake

cmake -B ./build/   
cmake --build ./build/ --config Release

The compiled shared libraries

The shared libraries libseuif97.dll building with MinGW-GCC/GCC are available in the /shared_lib/ directory:

• Windows(x64)
• Windows(x86)
• Liunx(x64)

Functions of the SEUIF97 Shared Library

The SEUIF97 library provides comprehensive functions for calculating water and steam properties, as well as the thermodynamic processes of steam turbines.

Water and Steam Properties

SEUIF97 supports 12 distinct input state pairs for calculating 36 thermodynamic, transport, and derived properties (see Properties).

Input Pairs:

• $(p,t), (p,h), (p,s), (p,v)$
• $(t,h),(t,s), (t,v)$
• $(p,x), (t,x),(h,x),(s,x)$
• $(h,s)$

The type of property functions are provided in the package

  ??(in1,in2,o_id)

• the first,second input parameters : the input property pairs
• the third input parameters: the ID of the calculated property - o_id
• the return: the calculated property value of o_id

Thermodynamic Process of Steam Turbine

• Isentropic Enthalpy Drop：ishd(pi,ti,pe)

    pi - inlet pressure(MPa); ti -inlet temperature(°C)
    pe - outlet pressure(MPa)

• Isentropic Efficiency(0~100)： ief(pi,ti,pe,te) (superheated steam zone)

      pi - inlet pressure(MPa);  ti - inlet temperature(°C)
      pe - outlet pressure(MPa); te - outlet temperature(°C)

The Function Prototype in C

// Functions of Properties
double pt(double p, double t, int o_id);
double ph(double p, double h, int o_id);
double ps(double p, double s, int o_id);
double pv(double p, double v, int o_id);

double th(double t, double h, int o_id);
double ts(double t, double s, int o_id);
double tv(double t, double v,  int o_id);

double hs(double h, double s,  int o_id);

double px(double p, double x,  int o_id);
double tx(double t, double x,  int o_id);
double hx(double h, double x,  int o_id);
double sx(double s, double x,  int o_id);

//The Functions for Thermodynamic Process of Steam Turbine
double ishd(double pi, double ti, double pe);
double ief(double pi, double ti, double pe, double te);

Using SEUIF97 library

To use the shared library in your preferred programming language, follow these steps:

1. Put the shared library in the default path of OS or the programming language

   • Windows(x86/64)

     • copy libseuif97.dll in the Windows/x86 or Windows/x64 folder to a default path of Windows32/64's DLL,for example: C:\Windows\System

   • Linux(x64)

     • copy libseuif97.so in the Linux/x64 folder to a default path of Linux shared lib : /usr/lib/

2. Add the specific API file for your programming language to its correspondingAPI path.

   • Note: API paths vary by language. Please refer to the specific Examples provided for your programming language to locate the correct path and setup instructions.

Interfaces and Examples

Interfaces and examples are provided in the /demo/ directory, supporting a wide range of languages and environments

• C/C++, Python, C#, Java, Excel VBA, MATLAB, Rust, Fortran, Pascal, Golang, Modelica

You can modify the provided interfaces to match your own API needs.

Language	Interface
C/C++	seuif97.h
Python	seuif97.py
C#	seuif97.cs
Excel VBA	seuif97.bas
Java	seuif97.java
MATLAB64	seuif97.m
Rust	seuif97.rs
Fortran	seuif97.f08
Pascal	seuif97.pas
Modelica	seuif97.mo
Golang	Example demo.go

The Selected Examples

Python

• T-S Diagram

• H-S Diagram

• H-S Diagram of Steam Turbine Expansion

C++

• H-S Diagram of Steam Turbine Expansion

Properties

Property	Unit	Symbol	o_id
Pressure	MPa	p	0
Temperature	°C	t	1
Density	kg/m^3	ρ	2
Specific Volume	m^3/kg	v	3
Specific enthalpy	kJ/kg	h	4
Specific entropy	kJ/(kg·K)	s	5
Specific exergy	kJ/kg	e	6
Specific internal energy	kJ/kg	u	7
Specific isobaric heat capacity	kJ/(kg·K)	cp	8
Specific isochoric heat capacity	kJ/(kg·K)	cv	9
Speed of sound	m/s	w	10
Isentropic exponent		k	11
Specific Helmholtz free energy	kJ/kg	f	12
Specific Gibbs free energy	kJ/kg	g	13
Compressibility factor		z	14
Steam quality		x	15
Region		r	16
Isobaric cubic expansion coefficient	1/K	ɑv	17
Isothermal compressibility	1/MPa	kT	18
Partial derivative (∂V/∂T)p	m^3/(kg·K)	(∂V/∂T)p	19
Partial derivative (∂V/∂P)T	m^3/(kg·MPa)	(∂V/∂P)T	20
Partial derivative (∂p/∂t)v	MPa/K	(∂p/∂t)v	21
Isothermal throttling coefficient	kJ/(kg·MPa)	δt	22
Joule-Thomson coefficient	K/MPa	μ	23
Dynamic viscosity	kg/(m·s)	η	24
Kinematic viscosity	m^2/s	ν	25
Thermal conductivity	W/(m.K)	λ	26
Thermal diffusivity	um^{2}/s	a	27
Prandtl number		Pr	28
Surface tension	N/m	σ	29

Publications

• 王培红,贾俊颖,程懋华. 水和水蒸汽热力性质IAPWS-IF97公式的通用计算模型[J]. 动力工程,2001,21(6)：1564-1567 [ pdf ]

• 芮嘉敏,孙振业,程懋华. 基于最短加法链状态空间树的IAPWS-IF97快速计算方法[J]. 汽轮机技术,2017,59(4):245-247 [ pdf ]

Cite as

• Cheng Maohua. (2023). The C implementation of the high-speed IAPWS-IF97 package: SEUIF97 (1.2.0). Zenodo. https://doi.org/10.5281/zenodo.8242452