# 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

| 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|