absorptionlib

absorptionlib

This package contains thermophysical property functions for the following aqueous solutions used in absorption systems:

• NaOH-water
• LiBr-water
• LiCl-water
• CaCl2-water

If you use this package, please cite:

Höffner et al. 2025 — Potentials of absorption thermal energy storage systems in seasonal application

DOI: https://doi.org/10.18462/iir.tptpr2025.1130

Installation and Usage

pip install absorptionlib

# Import
from absorptionlib import NaOH, LiBr, LiCl, CaCl2

# Example Usage
p = 100000  # [Pa]
x = 0.4     # [kg NaOH / kg solution]
t_sat = NaOH.saturation_temperature(x, p)
print(round(t_sat, 2))

Output

129.75

Units

All functions use the same units throughout the package:

Warnings and errors

Each function checks its inputs against the validity range of the underlying correlation:

• Inputs outside the validated range emit an OutOfRangeWarning (the value is still computed and returned).
• State points below the crystallization line emit a CrystallizationWarning.
• Physically invalid inputs raise a ValueError.

Every property function accepts prevent_errors=True, which suppresses all warnings and returns float('nan') instead of raising a ValueError — useful inside optimizers and root finders:

NaOH.enthalpy(0.4, 80, prevent_errors=True)

Warnings can also be controlled globally:

import absorptionlib
absorptionlib.disable_warnings()   # silence all package warnings
absorptionlib.enable_warnings()    # restore them

# or with the standard library, e.g. turn warnings into exceptions:
import warnings
warnings.filterwarnings("error", category=absorptionlib.CrystallizationWarning)

Quick documentation

Each submodule has its own "in-line" documentation, which can be called with the documentation() function. Each property function has a docstring, which can be printed with the explain() function.

# How to get quick documentation on the modules
NaOH.documentation()  # or LiBr, LiCl, CaCl2

# How to get quick documentation for functions
NaOH.explain("enthalpy")    # prints docstring of NaOH.enthalpy
LiCl.explain("pTDiagram")   # prints docstring of LiCl.pTDiagram

Available Property Functions

Diagrams

You can construct diagrams (pT-diagram, hx-diagram, crystallization curve) with the package. For example:

NaOH.pTDiagram()

Note: The plots can be styled with the usual matplotlib syntax. If the plot should be editable, use NaOH.pTDiagram(editablePlot=True). To reproduce the same-looking plot, set up matplotlib using:

import matplotlib.pyplot as plt
plt.rcParams['font.family'] = 'Georgia'
plt.rcParams['mathtext.fontset'] = 'custom'
plt.rcParams['mathtext.rm'] = 'Georgia'
plt.rcParams['mathtext.it'] = 'Georgia:italic'