realtpl (real gas thermodynamic python library) computes the density (rho), heat capacity (cp), speed of sound (sound), viscosity (visc) and heat conductivity (lambda) using a thermodynamic model based on cubic equations of state (EoS) and compares it with reference data from the open source library CoolProp. The cubic EoS are the well-known Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) EoS and the more sophisticated three-parameter Redlich-Kwong-Peng-Robinson (RKPR) EoS. The latter employs the critical compressibility factor for the EoS parameters, for details see reference Trummler et al.. The current implementation is primarily designed to evaluate results over a temperature range (with defined number of temperature steps) for a given pressure level. The data is displayed graphically and can also be exported to csv files for further processing. The only mandatory input is the fluid name, the temperature range and the pressure. Moreover, there is the additional feature to evaluate the data over a desired temperature and pressure range aiming to support table generations.

Fluid properties, such as mass, critical pressure etc., are directly extracted from CoolProp. This data is also saved to the output directory (specified in the configuration file) as <fluidname>.out. For the calculation of the heat capacity a reference value has to be evaluated, which is done using the NASA 7 or 9 coefficient polynomials. Therefore, the corresponding coefficients have to be provided. For selected fluids, we have already generated a database in the corresponding file - nasa_7.yaml or nasa_9.yaml. More data can be found in the references provided in the header of these files.

A special feature of realtpl is that all calculations with the suggested thermodynamic model are vectorized, making them very fast.

realtpl is open-source software (under GNU GPL License) for physicists, engineers, scientists, technicians and anyone interested in real gas thermodynamics. It runs on all operating systems which support Python, is quick to install, free of charge and designed to be easy to use. The indented use is to run the executable and modify the configuration files only.

realtpl has been specifically designed to be used for CFD simulations. Checking the accuracy of a thermodynamic model in advance is a central step before conducting CFD simulations. For different fluids as well as different pressure and temperature ranges, such an evaluation can be complicated and especially time-consuming. To this end, we have written realtpl to easily compare the results obtained with a thermodynamic model based on cubic EoS. For more details see reference Trummler et al..

realtpl is available as a Python package. Using pip you can simply install it with:

 pip install realtpl

Additionally, realtpl is also available on github https://github.com/ttrummler/realtpl. Clone the latest version with:

git clone https://github.com/ttrummler/realtpl

And proceed to install (use the -e option for an editable installation):

cd realtpl
pip install .

After installation, you will have an executable named realtpl, which you can run anywhere.

Testing is configured using tox. If not already installed, install tox using pip

pip install tox

Then, you can simply enter the tox and the tests will automatically be executed

tox

Note that it might not run for all tested python versions (py38, py39, py310) on your OS.

To run the test example use

realtpl --config /path/to/tests/example/config.yaml

In the configuration file everything for the computation is specified.

See tests/example/ for example configuration files. A minimum working example for the configuration file reads:

fluid_name: nHexane
pressure_Pa: 6.0e+06
temperature_start_K: 300
temperature_end_K: 600

Note that pressure and temperature input has to be in the SI units Kelvin and Pascal, as also indicated in the parameter names.

Additional optional configuration parameters are:

fluid_name: nHexane
eos_list: [SRK, PR, RKPR] # optional; default: SRK, PR, RKPR;
include_ref_data: true # optional; default: true
pressure_Pa: 6.0e+06
temperature_start_K: 300
temperature_end_K: 600
temperature_step_K: 1 # optional; default: 1
n_nasa_coeff: 7 # optional; default: 7
output_dir: results # optional; default: results
save_data_to_csv: true # optional;
show_plots: false # optional; default: true
save_plots: true # optional; default: false
show_deviation: true # optional; default: false
save_deviation: true # optional; default: false
performance_tracking: true # optional; default: false

Apart from that, also evaluations for a pressure and temperature range are possible. However, then no graphical output can be activated.

fluid_name: nHexane
eos_list: [SRK, PR, RKPR]
include_ref_data: true
pressure_start_Pa: 4.0e+06
pressure_end_Pa: 8.0e+06
pressure_step_Pa: 1.0e+06
temperature_start_K: 300
temperature_end_K: 600
temperature_step_K: 100
n_nasa_coeff: 7
output_dir: results
save_data_to_csv: true
show_plots: false
save_plots: false

The configuration data used for the calculation is written out to the output directory to config_data.out.

The selection of fluids (fluid_name) is limited by the availability of corresponding NASA coefficients in the data files nasa_X.yaml. Currently available fluids are listed at the end of this description.

The latest development version of realtpl can be obtained at

https://github.com/ttrummler/realtpl

To report bugs, please use realtpl’s Bug Tracker at:

https://github.com/ttrummler/realtpl

See LICENSE for information on the terms & conditions for usage of this software, and a DISCLAIMER OF ALL WARRANTIES.

Cite realtpl if used in your work or to generate data required for your work. Cite as: Trummler, T., Glatzle, M., Doehring, A., Urban, N., Klein, M., Thermodynamic modeling for numerical simulations based on the generalized cubic equation of state.

NOTE the license for the included database of the 7 coefficient NASA polynomials used for the calculation of the caloric properties. Using this data requires proper citation to be included in the pertinent publications. Cite: Goos, E., Burcat, A., Ruscic, B.. New NASA Thermodynamic Polynomials Database With Active Thermochemical Tables updates. Report ANL 05/20 TAE 960.

To cite realtpl in publications use:

Trummler, T., Glatzle, M., Doehring, A., Urban, N., Klein, M., Thermodynamic modeling for numerical simulations based on the generalized cubic equation of state.

The selection of fluids (fluid_name) is limited by the availability of corresponding NASA coefficients in the data files nasa_X.yaml. Extensions are possible at any time and can be achieved by simply adding the correct data in the file nasa_7.yaml or nasa_9.yaml. The currently available fluids are listed below. Please pay attention to the identical spelling of the fluid names in the configuration file.

NASA 7 coefficient polynomials (n_nasa_coeff: 7):

• Nitrogen
• nDodecane
• nHexane
• Cyclohexane
• Cyclopentane
• Methane
• Methanol
• Ethanol
• Propane
• Butane
• nPentane
• CarbonDioxide

NASA 9 coefficient polynomials (n_nasa_coeff: 9):

• Nitrogen
• Hydrogen
• nDodecane
• nHexane
• Cyclopentane
• Cyclohexane
• Propane
• Methane
• CarbonDioxide
• Methanol
• Ethanol