RAMDECOM

Calculation routine to calculate the decompression wave speed for pipeline design to ensure adequate pipe thickness and/or Charpy-V hardness so a running fracture can be arrested. The program is mainly targeted for CO₂, but almost any fluid can be modelled.

This code is developed by Anders Andreasen and is open source and published under an MIT license . For pure fluids, calculations can be made using open source tools only (CoolProp). However, if calculations shall be made for mixtures a REFPROP license and installation is required.

Installation

The code is still under heavy development and official releases and pip/conda packages have not been prepared yet. Installation is done by cloning the code to a local directory and running

cd directory pip install -e .

This way a dynamic link is created in the local site-packages directory. Any changes to the code will be dynamically updated, so no need to run pip install -e every time the code is updated.

Usage

Import main class

from ramdecom import wavespeed

Define input

input = {} input['eos'] = 'HEOS' input['fluid'] = 'CO2' input['pressure'] = 130e5 input['temperature'] = 320

The equation of state can either be HEOS for the CoolProp pure component Helmholtz energy formulation or REFPROP. For mixtures only REFPROP works. In case REFPROP is selected additional optional input for specifying either the GERG-2008 or the Peng-Robinson equation of state can be given. The follwoing optional input can also be provided:

input['extrapolate'] = True

which will extrapolate the end point in the decompression curve to zero pressure.

input['pressure_step'] = 1e5

defines the step length when stepping down from the initial pressure along the isentropic path. The default value is 1 bar and has been found to be adequate.

input['pressure_break'] = 1e5

can break the isentropic decompression calculation e.g. if the calculation routine in the thermodyanmic backend raises an exception. By breaking before the exception is raised, partial results can be inspected and visualised.

Ininitialize and run

ws = wavespeed.WaveSpeed(input) ws.run()

Plotting

ws.plot_decom(filename='out.png',data=data)

If the optional input data (experimental data or other calculation for comparison) is provided this shall be a nx2 array with decompression wave speed in the first column and pressure in the second column. If the optional input filename is not provided the plot is displayed on-screen without being saved to file.

Other data output

A data file with calculation results can be saved to csv

ws.get_result_file() The results are saved to decom_result.csv or if the optional input filename is given, it is saved to the provided path.

Methods and theory

Some basic theory and description of the code is included with the draft paper located in

ramdecom\paper\

Further some relevant references for further reading:

[1] http://pubs.acs.org/doi/abs/10.1021/ie4033999

[2] https://pubs.acs.org/doi/10.1021/acsomega.1c01360

[3] https://doi.org/10.18434/T4/1502528

[4] https://doi.org/10.1016/j.psep.2018.08.034

[5] https://doi.org/10.1115/1.4031941

[6] https://doi.org/10.1115/1.4034016