Table of contents
- Example usage
- Copyright and license
Psychrometrics are the study of physical and thermodynamic properties of moist air. These properties include, for example, the air's dew point temperature, its wet bulb temperature, relative humidity, humidity ratio, enthalpy.
The estimation of these properties is critical in several engineering and scientific applications such as heating, ventilation, and air conditioning (HVAC) and meteorology. Although formulae to calculate the psychrometric properties of air are widely available in the literature (@Stull2011; @Wexler1983; @Stoecker1982; @Dilley1968; @Humphreys1920), their implementation in computer programs or spreadsheets can be challenging and time consuming.
Functions for the calculation of dew point temperature, wet-bulb temperature, partial vapour pressure of water, humidity ratio or relative humidity, knowing any other of these and dry bulb temperature and atmospheric pressure.
Functions for the calculation of other moist air properties. All these use the humidity ratio as input.
Relationships between these various functions are illustrated in Figure 1. To compute a moist air property such as enthalpy, knowing a humidity parameter such as dew point temperature, one first has to compute the humidity ratio from the dew point temperature, then compute the enthalpy from the humidity ratio. The functions in point (1) above include primary relationships corresponding to formulae from the ASHRAE Handbook, and secondary relationships which use a combination of primary relationships to calculate the result. For example, to compute dew point temperature knowing the partial pressure of water vapor in moist air, the library uses a formula from the ASHRAE Handbook (primary relationship). On the other hand to compute dew point temperature from relative humidity, the library first computes the partial pressure of water vapor, then computes the dew point temperature (secondary relationship). Primary relationships are shown with bold double arrows in Figure 1.
Figure 1 - Psychrometric relationships.
To install or bundle the library as part of your program see the language-specific instructions below -- there are no external dependencies required.
PsychroLib is available though the Python Package Index (PyPI) and can be installed using
pip install psychrolib.
C, Fortran, JS and VBA
Clone the repository, or download the file directly from the repository, and include PsychroLib to your code according to the language specifications.
If you are using PsychroLib, we ask to please cite both the article, and the software. For the article, cite as follows:
Meyer, D., & Thevenard, D. (2019). PsychroLib: a library of psychrometric functions to calculate thermodynamic properties of air. Journal of Open Source Software, 4(33), 1137. https://doi.org/10.21105/joss.01137
For the software, please cite the specific PsychroLib version you are using as listed on Zenodo -- see https://doi.org/10.5281/zenodo.2537945
If you are looking to contribute, please read our Contributors' guide for details.
This project uses semantic versioning.
Copyright and license
Copyright (c) 2018 D. Thevenard and D. Meyer for the current library implementation.
Copyright (c) 2017 ASHRAE Handbook — Fundamentals (https://www.ashrae.org) for equations and coefficients published ASHRAE Handbook — Fundamentals Chapter 1.
Licensed under the MIT License.