Coupled Thermodynamic BOSfluids-Jive Simulations

BOSfluids Thermodynamic Module
BOSfluids is known for its steady state, quasi steady state and transient flow solvers and the more recent interface to the structural solver of ANSYS. Recently the steady state solver of BOSfluids has been extended with a thermodynamic module. That is, given thermal boundary conditions, BOSfluids calculates the temperature profile within the fluid by taking into account heat transfer due to convection and conduction, heat exchange with the environment and heat generation due to friction. In the steady state solver the flow calculations have been coupled to thermodynamic calculations by using the flow rate and pressure, obtained by the flow calculations, as input for the thermodynamic calculations and subsequently by using the temperature, obtained by the thermodynamic calculations, to adjust the fluid properties in the flow calculations. This process is repeated until the solutions of the flow and thermodynamic calculations are consistent.

Coupled BOSfluids-Jive Simulations
The thermodynamic module of BOSfluids was developed for a recent project at DRG. In this project a section of the piping is contained in a solid medium with an initial temperature gradient. The fluid through the piping has a fixed inlet flow rate and inlet temperature and is heated along the pipe line due to heat transfer with the medium. One of the goals of the project was to determine the output temperature of the fluid. The fluid drains energy from the medium, because the incoming fluid is colder than the medium, and therefore the temperature of the medium changes with time. To account for this behavior the heat transfer within the medium was modelled by means of a finite element model using Jive, a software toolkit provided by DRG.

The finite element and BOSfluids simulations were coupled by updating the boundary conditions of both simulations at the interface of the fluid and the medium after each time step (the pipe wall was taken into account as an additional heat transfer resistance). The steady state solver of BOSfluids could be used, because the temperature of the medium changes much slower than the temperature of the fluid. The temperature of the medium can therefore be considered a constant boundary condition in the fluid simulations.

Figure 1 shows the results of a coupled simulation. The fluid is heated along the pipe line due to the heat transfer from the medium to the fluid. The temperature within the medium is slowly decreasing starting at the centerline, due to the energy drained by the piping. Subsequently, the heat transfer from the medium to the fluid decreases and thus also the outlet temperature of the fluid. This effect, however, occurs mainly in when the fluid starts to flow and diminishes rapidly.

Figure 1: The time dependent behavior of the temperature for a solid medium (left) containing a pipe section (right). The heat transfer within the solid medium is modelled using the finite element toolkit Jive and the temperature of the fluid in the pipe section is modelled by BOSfluids. The results of both analyses are coupled at the interface as a boundary condition.

Future Developments
This project illustrates how the engineering and software divisions of DRG reinforce each other. The software division can assist in extending its software or interfacing the software to other software packages so that the engineering division is not limited to using out-of-the-box software solutions only. Subsequently, these extensions or interfaces can be integrated in the software packages developed by DRG. The thermodynamic module developed for this project will be further improved and extended so that it meets the high quality standards of DRG software and it will become available in a future release.

For more information, please contact:

Tim Gebraad
Senior Software Engineer

Phone: +31 85 058 00 46

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