1 stable release

1.1.4 Sep 4, 2023
1.1.3 Sep 3, 2023
1.1.1 Aug 15, 2023

#57 in Science

MIT license

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This is the Rust implementation of the high-speed IAPWS-IF97 package seuif97 with C and Python binding. It is suitable for computation-intensive calculations,such as heat cycle calculations, simulations of non-stationary processes, real-time process monitoring and optimizations.

Through the high-speed package, the results of the IAPWS-IF97 are accurately produced at about 5-20x speed-up compared to using the powi() of the Rust standard library in the forloop directly when computing the basic equations of Region 1,2,3.

The Fast Methods

  1. The multi-step method unleashes the full power of the compiler optimizations while using powi() with the for loop
  2. The recursive method computes the polynomial values of the base variable and its derivatives

In the package, 36 thermodynamic, transport and further properties can be calculated.

The following 12 input pairs are implemented:

(p,t) (p,h) (p,s) (p,v) 

(t,h) (t,s) (t,v) 

(p,x) (t,x) (h,x) (s,x) 



Install the crate

cargo add seuif97

The type of functions are provided in the package:

struct o_id_region_args {
   o_id: i32,
   region: i32,

fn<R>(f64,f64,R) -> f64
    R: Into<o_id_region_args>,
  • the first,second input parameters(f64) : the input propertry pairs
  • the third and fourth input parametes:
    • the third : the property ID of the calculated property - o_id
    • the fourth option parameter: the region of IAPWS-IF97
  • the return(f64): the calculated property value of o_id





use seuif97::*;
fn main() {
    let p:f64 = 3.0;
    let t:f64= 300.0-273.15;
    let h=pt(p,t,OH);
    let s=pt(p,t,OS);
    // set the region
    let v=pt(p,t,(OV,1));
    println!("p={p:.6} t={t:.6} h={t:.6} s={s:.6} v={v:.6}");   

The C binding

Building the dynamic link library

  • cdecl
cargo build -r --features cdecl
  • stdcall: Win32 API functions
cargo build -r --features stdcall

The convenient compiled dynamic link libraries are provided in the ./dynamic_lib/

The functions in C

double pt(double p,double t,short o_id);
double ph(double p,double h,short o_id);
double ps(double p,double s,short o_id);
double pv(double p,double v,short o_id);

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

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

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


#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define OH 4
#define OS 5

extern double pt(double p,double t,short o_id);

int main(void)
    double p = 16.0;
    double t = 530.0;
    double h = pt(p, t, OH);
    double s = pt(p, t, OS);
    printf("p,t %f,%f h= %f s= %f\n", p, t, h, s);
    return EXIT_SUCCESS;

The Example of Rankine Cycle Analysis

The Python binding


pip install seuif97


from seuif97 import *


# ??(in1,in2,o_id)
# ??2?(in1,in2)
print(f"p={p}, t={t} h={h:.3f} s={s:.3f}")


T-S Diagram


Propertry Unit Symbol o_id o_id(i32)
Pressure MPa p OP 0
Temperature °C t OT 1
Density kg/m³ ρ OD 2
Specific Volume m³/kg v OV 3
Specific enthalpy kJ/kg h OH 4
Specific entropy kJ/(kg·K) s OS 5
Specific exergy kJ/kg e OE 6
Specific internal energy kJ/kg u OU 7
Specific isobaric heat capacity kJ/(kg·K) cp OCP 8
Specific isochoric heat capacity kJ/(kg·K) cv OCV 9
Speed of sound m/s w OW 10
Isentropic exponent k OKS 11
Specific Helmholtz free energy kJ/kg f OF 12
Specific Gibbs free energy kJ/kg g OG 13
Compressibility factor z OZ 14
Steam quality x OX 15
Region r OR 16
Isobari cubic expansion coefficient 1/K ɑv OEC 17
Isothermal compressibility 1/MPa kT OKT 18
Partial derivative (∂V/∂T)p m³/(kg·K) (∂V/∂T)p ODVDT 19
Partial derivative (∂V/∂p)T m³/(kg·MPa) (∂v/∂p)t ODVDP 20
Partial derivative (∂P/∂T)v MPa/K (∂p/∂t)v ODPDT 21
Isothermal throttling coefficient kJ/(kg·MPa) δt OIJTC 22
Joule-Thomson coefficient K/MPa μ OJTC 23
Dynamic viscosity Pa·s η ODV 24
Kinematic viscosity m²/s ν OKV 25
Thermal conductivity W/(m.K) λ OTC 26
Thermal diffusivity m²/s a OTD 27
Prandtl number Pr OPR 28
Surface tension N/m σ OST 29
Static Dielectric Constant ε OSDC 30
Isochoric pressure coefficient 1/K β OPC 31
Isothermal stress coefficient kg/m³ βp OBETAP 32
Fugacity coefficient fi OFI 33
Fugacity MPa f* OFU 34
Relative pressure coefficient 1/K αp OAFLAP 35

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