# Library of functions

All material-independant values, universal constants and state equations are stored within the `hamopy/ham_library`

file. In addition to constant properties such as the latent heat of evaporation, the universal gas constant and the thermal conductivity of air, the file includes 5 useful methods:

`p_sat(T)`

: Water vapor saturation pressure (Pa)`D_va(T)`

: Water vapor diffusivity in air (m2/s)`p_v(p_c, T)`

: Water vapor pressure (Pa)`HR(p_c, T)`

: Relative humidity`p_c(HR, T)`

: Capillary pressure (Pa)

The last three methods are equivalent formulations of the Clausius-Clapeyron equation. It is used to calculate the relative humidity from values of the capillary pressure, and inversely.

Here is an example of use:

```
from hamopy import ham_library as ham
ham.cp_liq
ham.p_sat(280)
ham.p_c(0.92, 299)
```

This script first returns the value of the liquid water specific heat, then the water vapor saturation pressure at 280 K, then the capillary pressure at 92 %RH and 299 K.