Abstract
Local ventilation is widely used in industry for
controlling airborne contaminants. However, the present
design practices of local ventilation systems are mainly
based on empirical equations and do not take
quantitatively into account the various factors affecting
the performance of these systems. The aim of this study
was to determine the applicability and limitations of
more advanced fluid mechanical methods to the design and
development of local ventilation systems. The most
important factors affecting the performance of local
ventilation systems were determined and their effect was
studied in a systematic manner. The numerical
calculations were made with the FLUENT computer code and
they were verified by laboratory experiments, previous
measurements or analytical solutions.
The results proved that the numerical calculations can
provide a realistic simulation of exhaust openings,
effects of ambient air flows and wake regions. The
experiences with the low-velocity local supply air showed
that these systems can also be modelled fairly well. The
results were used to improve the efficiency and thermal
comfort of a local ventilation unit and to increase the
effective control range of exhaust hoods.
In the simulation of the interaction of a hot buoyant
source and local exhaust, the predicted capture
efficiencies were clearly higher than those observed
experimentally. The deviations between measurements and
non-isothermal flow calculations may have partly been
caused by the inability to achieve grid independent
solutions.
CFD simulations is an advanced and flexible tool for
designing and developing local ventilation. The
simulations can provide insight into the time-averaged
flow field which may assist us in understanding the
observed phenomena and to explain experimental results.
However, for successful calculations the applicability
and limitations of the models must be known.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 26 May 1997 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-5052-8 |
Publication status | Published - 1997 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- ventilation
- indoor air
- air flow
- exhaust systems
- gas dynamics