# IF97
The **if97** is the Python API of the high-speed IAPWS-IF97 package in Rust. 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 `for`loop 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 if97, [36 thermodynamic, transport and further properties](#properties) can be calculated.
The following 12 input pairs are implemented:
```txt
(p,t) (p,h) (p,s) (p,v)
(p,x) (t,x) (h,x) (s,x)
(t,h) (t,s) (t,v)
(h,s)
```
## The functions
The type of functions are provided in the if97 package:
```python
??(in1,in2,o_id)
```
* the first,second input parameters : the input propertry pairs
* the third input parametes: the property ID of the calculated property - [o_id](#properties)
* the return: the calculated property value of o_id
```python
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)
```
## Examples
```python
from if97 import *
OH=4
OS=5
p=16.0
t=535.1
h=pt(p,t,OH)
s=pt(p,t,OS)
print(f"p={p}, t={t} h={h:.3f} s={s:.3f}")
```
## Properties
| 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|