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Code for calculating depressurization / blowdown of pressure vessels accompanying a paper accepted for publication in Process Safety Progress.

Download or clone the code and install from the the openthermo directory (no official pypi package yet)

NOTE: Although rigorously validated, this code shall be considered as work-in-progress and experimental. Several elements have been left out of this public version such as a VLLE-flash based on legacy code.

pip install -e .

To reproduce results from the paper

cd tests
python test_blowdown.py

Uncomment the case in the main function to be analysed.

The code considers a vessel filled with a fluid at time equals zero. Fluid is discharged through an orifice. As mass is discharged the pressure and temperature drops over time, where heat can be exchanged through the vessel wall with the surroundings. Since both mass and heat can be exchanged with the surroundings it constitutes an open thermodynamic system hence the name of the code: openthermo.

The code uses a multi-component real-gas equation of state (either Peng-Robinson or Soave-Redlich-Kwong) to describe the system. Two phases can be handled by the code, occuring at any time during the depressurisation process.

openthermo can either assume full equilibrium between gas and liquid or partial equilibrium. In both cases the vessel material temperature may be different depending on contact with either gas or liquid (different heat transfer rates). In the partial equilibrium approach gas and liquid may also achieve different temperatures, The partial equilibrium approach is emulating the methodology of VBsim by Terenzi et al. and is comparable to legacy codes BLOWDOWN from Imperial College and BLOWSIM from University College London. To the best of our knowledge this is the first ever rigorous blowdown simulation tool which can manage partial equilibrium available as open source.

This codes relies heavily on the thermo package by Caleb Bell, with the core flash calculation replaced by thermopack from SINTEF for increased stability and speed. openthermo builds partially on HydDown and has also been inspired by HYRAM+ for the ODE integration part.

The following packages are scaffolding openthermo:

• thermopack
• thermo
• fluids
• ht
• chemicals
• numpy
• scipy
• matplotlib
• SciencePlots

The code has been validated against available experimental data from the literature (see paper).

Wall temperature:

Fluid temperature: