Python Plotting

Note

Please see also the new project CoolPlot, aiming to build upon the routines in CoolProp for plotting.

The simplest and most straight forward use case is the generation of plots with default isolines and spacing. Here is a brief example to demonstrate how to create a pressure-enthalpy (\(\log p,h\)) plot for propane (R-290) with automatic isoline spacing:

import CoolProp
from CoolProp.Plots import PropertyPlot
plot = PropertyPlot('R290', 'ph')
plot.calc_isolines()
plot.show()

(Source code, png, .pdf)

Note

Running the example above in your own environment will print many UserWarning messages (over 1,000) that start with “An error occurred for inputs”. This is expected and does not mean anything is wrong with your installation. To draw complete isolines, CoolProp calculates points right up to, and beyond, the temperature and pressure limits of the fluid. Where the fluid has no valid state, that point is skipped and the line simply has a gap there. The lowest-density line is valid only in a small corner of the plot, so you will also see one “Poor data quality” message for it, and that line is short for the same reason. If you would rather not see the messages, you can ignore them in your script with warnings.filterwarnings("ignore", message="An error occurred for inputs") (and the same with message="Poor data quality").

The following example can be used to create a temperature-entropy (\(T,s\)) plot for propane (R290) with isolines for the vapour quality in steps of 0.2:

import CoolProp
from CoolProp.Plots import PropertyPlot
ts_plot = PropertyPlot('R290', 'Ts', tp_limits='ORC')
ts_plot.calc_isolines(CoolProp.iQ, num=6)
ts_plot.show()

(Source code, png, .pdf)

The following example can be used to create a pressure-enthalpy (\(\log p,h\)) plot for R-134a with a couple of isotherms and isentropic lines:

import CoolProp
from CoolProp.Plots import PropertyPlot
plot = PropertyPlot('HEOS::R134a', 'PH', unit_system='EUR', tp_limits='ACHP')
plot.calc_isolines(CoolProp.iQ, num=11)
plot.calc_isolines(CoolProp.iT, num=25)
plot.calc_isolines(CoolProp.iSmass, num=15)
plot.show()

(Source code, png, .pdf)

Here is an example for R-245fa using two different ways to generate the isobars:

import CoolProp
from CoolProp.Plots import PropertyPlot
plot = PropertyPlot('HEOS::R245fa', 'TS', unit_system='EUR', tp_limits='ORC')
plot.calc_isolines(CoolProp.iQ, num=11)
plot.calc_isolines(CoolProp.iP, iso_range=[1,50], num=10, rounding=True)
plot.draw()
plot.isolines.clear()
plot.props[CoolProp.iP]['color'] = 'green'
plot.props[CoolProp.iP]['lw'] = '0.5'
plot.calc_isolines(CoolProp.iP, iso_range=[1,50], num=10, rounding=False)
plot.show()

(Source code, png, .pdf)

The available plots are listed in the CoolProp.Plots.Common.Base2DObject and at this time (May 2016) this list contains (\(T,s\)), (\(p,h\)), (\(h,s\)), (\(p,s\)), (\(p,\rho\)), (\(T,\rho\)), (\(p,T\)) and (\(p,u\)) plots.

Some of the commonly used Matplotlib functions, such as title(), grid(), xlabel() and ylabel() have been wrapped in the CoolProp.Plots.Common.BasePlot class to make the plotting of graphs a little simpler, for example:

import CoolProp
from CoolProp.Plots import PropertyPlot
ts_plot = PropertyPlot('Water', 'Ts')
ts_plot.calc_isolines(CoolProp.iQ, num=11)
ts_plot.title(r'$T,s$ Graph for Water')
ts_plot.xlabel(r'$s$ [kJ/kg K]')
ts_plot.ylabel(r'$T$ [K]')
ts_plot.grid()
ts_plot.show()

(Source code, png, .pdf)