Psychrochart

A python 3 library to make psychrometric charts and overlay information on them.

It implements a useful collection of psychrometric equations for moisture and humid air calculations, and the generation of beautiful and high customizable psychrometric charts in SVG with matplotlib.

Calculations are made by implementing experimental equations extracted from recognized sources, such as the 2009 ASHRAE Handbook—Fundamentals (SI).

Install

Get it from pypi or clone it if you want to run the tests.

pip install psychrochart

Features

• SI units (with temperatures in celsius for better readability).
• Easy style customization with a JSON template (colors, line styles and line widths).
• Psychrometric charts within temperature and humidity ratio ranges, for any pressure*, with:
  • Saturation line
  • Constant RH lines
  • Constant enthalpy lines
  • Constant wet-bulb temperature lines
  • Constant specific volume lines
  • Constant dry-bulb temperature lines (internal orthogonal grid, vertical)
  • Constant humidity ratio lines (internal orthogonal grid, horizontal)
• Plot legend for each family of lines
• Specify labels for each family of lines
• Overlay points, zones, arrows...
• Export SVG files
• Tested against example tables from http://www.engineeringtoolbox.com
• 100 % code coverage.

* The ranges of temperature, humidity and pressure where this library should provide good results are within the normal environments for people to live in. Don't expect right results if doing other type of thermodynamic calculations. Over saturated water vapor states are not implemented.

TODO list:

• Better Doc!
• Bokeh interactive psychrochart
• Overlay pd.Dataframe time indexed evolution objects

Changelog

• v0.1.0: Initial version.
• v0.1.1: Minor plotting fixes, set axis position, define P with altitude_m or pressure_kpa, reuse plot removing annotations (chart.remove_annotations). Axes as internal prop, lazy plotting, save to disk helper (chart.save).
• v0.1.2: Add agg module to set that matplotlib backend.
• v0.1.3: Add custom params for plotting styles, option to exclude first and last tick (constant_{humid/temp}_label_include_limits).
• v0.1.4: Customize labels and its locations for families of psychrometric curves.
• v0.1.5: Add Arrows, compatibility with the Home Assistant component psychrometrics.
• v0.1.6: Some cleaning, better typing, flake8, added tox.ini.
• v0.1.7: Methods to clean the plot (.close_fig()) and to remove the legend (.remove_legend()).
• v0.1.8: Memleak with savefig.
• v0.1.10: Fix plot limits, do not use pyplot, axes are not optional.
• v0.1.11: Add optional Axes as argument for PsychroChart.plot.
• v0.1.12: Add empiric equation for wet bulb temperature (@ZhukovGreen contribution).
• v0.1.13: Add convex hull option for overlay points.
• v0.2.0: Hide output in verbose mode, better convex hull zones syntax, stable.
• v0.2.1: Make scipy an optional requirement (it's only used for the ConvexHull zone).
• v0.2.2: Fix initial conditions for iteration solvers
• v0.2.3: Handle ConvexHull exception, overlay of series of points.
• v0.2.4: Set ASHRAE formulation for saturation_pressure_water_vapor as default. Minimal adjustments to iteration solvers for enthalpy and specific volume.
• v0.2.5: Fix coefficient in ASHRAE formulation for dew_point_temperature.
• v0.2.6: Add labels for connectors in chart legend (@@zhang-shen contribution).

Usage

from psychrochart.chart import PsychroChart

# Load default style:
chart_default = PsychroChart()
axes = chart_default.plot()

Called from a terminal (python psychrochart), it plots and shows the default chart using the default matplotlib backend, equivalent to this python script:

from psychrochart.chart import PsychroChart
import matplotlib.pyplot as plt

PsychroChart().plot(ax=plt.gca())
plt.show()

Chart customization

The default styling for charts is defined in JSON files that you can change, or you can pass a path of a file in JSON, or a dict, when you create the psychrometric chart object. Included styles are: default, ashrae, interior and minimal.

from psychrochart.chart import PsychroChart
from psychrochart.util import load_config

# Load preconfigured styles:
chart_ashrae_style = PsychroChart('ashrae')
chart_ashrae_style.plot()

chart_minimal = PsychroChart('minimal')
chart_minimal.plot()

# Get a preconfigured style dict
dict_config = load_config('interior')

# Specify the styles JSON file:
chart_custom = PsychroChart('/path/to/json_file.json')
chart_custom.plot()

# Pass a dict with the changes wanted:
custom_style = {
    "figure": {
        "figsize": [12, 8],
        "base_fontsize": 12,
        "title": "My chart",
        "x_label": None,
        "y_label": None,
        "partial_axis": False
    },
    "limits": {
        "range_temp_c": [15, 30],
        "range_humidity_g_kg": [0, 25],
        "altitude_m": 900,
        "step_temp": .5
    },
    "saturation": {"color": [0, .3, 1.], "linewidth": 2},
    "constant_rh": {"color": [0.0, 0.498, 1.0, .7], "linewidth": 2.5,
                    "linestyle": ":"},
    "chart_params": {
        "with_constant_rh": True,
        "constant_rh_curves": [25, 50, 75],
        "constant_rh_labels": [25, 50, 75],
        "with_constant_v": False,
        "with_constant_h": False,
        "with_constant_wet_temp": False,
        "with_zones": False
    }
}

chart_custom_2 = PsychroChart(custom_style)
chart_custom_2.plot()

The custom configuration does not need to include all fields, but only the fields you want to change.

To play with it and see the results, look at this notebook with usage examples.

Tests

To run the tests, clone the repository and run:

export TESTING=1; py.test tests/ --cov=psychrochart -v --cov-report html; coverage report -m; export TESTING=;

to generate the coverage reports.

License

MIT license, so do with it as you like ;-)

Included styling examples

Default style:

ASHRAE Handbook black and white style:

Minimal style: