seuif97 2.3.8

The high-speed IAPWS-IF97 package in Rust with Python bindings

SEUIF97

SEUIF97 2, built on Rust, is a major upgrade over SEUIF97 1 built on C, delivering significant improvements in performance, functionality and ecosystem support.

SEUIF97 achieves a 5-20x speedup over naive implementations that use the Rust standard library's powi() in for loops for the basic equations of Regions 1, 2, 3,and 5.

It is suitable for computation-intensive calculations, such as heat cycle calculations, simulations of non-stationary processes, real-time process monitoring and optimizations.

This package supports 12 distinct input state pairs for calculating 36 thermodynamic, transport, and derived properties (see Properties), and thermodynamic process functions (see Thermodynamic Process Functions).

What's New in SEUIF97 2

Feature	1.*	2.*
Implementation	C	Rust
Calculation Speed	Baseline	~2× speedup
Supported Properties	30 properties	36 properties (+6 new)
Supported OS	Windows, Linux	Windows, Linux, macOS

Property Calculation API

The package provides two types of APIs.

Universal Property Functions

Each function accepts an input pair, an output property ID (o_id).

The following 12 input pairs are implemented:

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

th(t,h,o_id) ts(t,s,o_id) tv(t,v,o_id)

hs(h,s,o_id)

px(p,x,o_id) tx(p,x,o_id) hx(h,x,o_id) sx(s,x,o_id)

Note: Only linearly related thermodynamic properties are calculable in the wet steam region.

Direct Property Functions

The following 12 input pairs are implemented:

pt2h(p, t)  pt2s(p, t)  pt2v(p, t)  pt2x(p, t)
ph2t(p, h)  ph2s(p, h)  ph2v(p, h)  ph2x(p, h)   
ps2t(p, s)  ps2h(p, s)  ps2v(p, s)  ps2x(p, s)  
pv2t(p, v)  pv2h(p, v)  pv2s(p, v)  pv2x(p, v)  

th2p(t, h)  th2s(t, h)  th2v(t, h)  th2x(t, h)   
ts2p(t, s)  ts2h(t, s)  ts2v(t, s)  ts2x(t, s)  
tv2p(t, v)  tv2h(t, v)  tv2s(t, v)  tv2x(t, v)  

hs2p(h, s)  hs2t(h, s)  hs2v(h, s)  hs2x(h, s)    

px2t(p, x)  px2h(p, x)  px2s(p, x)  px2v(p, x)
tx2p(t, x)  tx2h(t, x)  tx2s(t, x)  tx2v(t, x)

hx2p(h, x)  hx2t(h, x)  hx2s(h, x)  hx2v(h, x)
sx2p(s, x)  sx2t(s, x)  sx2h(s, x)  sx2v(s, x)

Thermodynamic Process Functions

The following thermodynamic process functions are also available:

• ishd(pi, ti, pe): isentropic enthalpy drop for steam expansion (kJ/kg)
• ief(pi, ti, pe, te): isentropic efficiency for superheated steam expansion (%)

Usage

from seuif97 import  pt, pt2s

OH=4

p=16.0
t=535.1
# universal property function with o_id
h=pt(p,t,OH)
# direct property function
s=pt2s(p,t)
print(f"p={p}, t={t} h={h:.3f} s={s:.3f}")

Examples

• T-S Diagram

• H-S Diagram

• H-S Diagram of Steam Turbine Expansion

• The Hybrid Steady-state Simulator of Rankine Cycle in Python

Properties

Property	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
Isobaric 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	—	φ	OFI	33
Fugacity	MPa	f	OFU	34
Relative pressure coefficient	1/K	αp	OAFLAP	35