Complex Ventilation of Multiple Electrical Enclosure Systems. Development and comparision of 1D pipe-flow models.
Typ
Examensarbete för masterexamen
Program
Engineering mathematics and computational science (MPENM), MSc
Publicerad
2022
Författare
Andersson, Carl
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The nature of fluid flows in pipes is highly relevant to planning and constructing
cooling systems. Although general, conventional computational fluid dynamics
solutions such as ANSYS FLUENT, OpenFOAM or similar software exists, these
solutions are computationally expensive and require hours, if not days, to give results.
This study aims to explore and compare implicit solutions for complex pipe
networks that can be generated in a much quicker fashion. In this context, implicit
solutions refer to 1D-implementations which solve the entire pipe network as a set
of simultaneous equations, or in other words, a matrix.
In order to evaluate the accuracy of any such implicit solver, the results that the
solver produces are validated against a simulation run in ANSYS FLUENT using,
to the extent that it is possible, identical settings. A set of different cases are run
through this validation procedure in order to observe how the implicit flow rate
solver compares across a number of cases. The results show that while the implicit
flow rate solver manages to mimic the fluid flow of the ANSYS FLUENT simulations
with only small errors that arise primarily from observed asymmetries in the
ANSYS FLUENT simulation. The implicit flow rate solver does however produce
significant errors in temperature prediction when cooling systems that have heat
sources approximating 2 · 105 W/m3 applied at smaller regions. Additionally, the
results show an extreme benefit in terms of run-time, on the order of 103 compared
to ANSYS FLUENT.
These results suggest that the implicit solver fails to capture a variety of phenomena,
particularly related to cases applying larger additional heat sources. These phenomena
would need to be captured if it is to act as a predictor of the behavior of such
cases. For cases without the previously mentioned large heat source however, the
results suggest that the implicit solver can serve as a semi-accurate run-time efficient
predictor. Additionally, the results suggest that the usage of minor loss coefficients
or length-equivalents for estimating the pressure drop over a pipe bend, T-junction
or similar structures is insufficient to capture combined effects of said structures in
more complex pipe networks. Finally, observation of the errors in temperature prediction
suggest an approximately linear behavior. On this basis, the implicit solver
or a variant of it could very well serve as an early predictor when iterating through
system design in order to quickly find designs that will fail to fulfill certain criteria.
Beskrivning
Ämne/nyckelord
CFD, Pipe flow, fluid dynamics, ventilation, MATLAB, ANSYS FLUENT