Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Increased awareness of environmental problems has awakened interest in
renewable energy systems. Natural ventilation systems are especially of interest,
as people spend most of their time indoors. Indoor air quality is an
important consideration when human health and occupant comfort is to be
maintained.
This study focusses on determining the best inlet and outlet shape for a
natural ventilation system from a chosen set of configurations. The inlet and
outlet configurations were tested on a PDEC (Passive Downdraught Evaporative
Cooling) shaft and solar chimney. The PDEC incorporated an evaporative
cartridge made from cotton cloth. Independent models of the PDEC and solar
chimney were built in a thermally controlled space where the configurations
were tested at different wind speeds. The configurations were tested on a wet
or dry PDEC shaft and on a hot or cold solar chimney.
One-dimensional finite difference models, accounting for some two-dimensional
effects in the evaporative cartridge, of the cartridge and solar chimney were
developed. CFD (Computational Fluid Dynamics) models were further constructed
in FLUENTr, simulating operating conditions for each inlet and outlet
test. The CFD models were constructed to obtain numerical comparisons
for the experimental data. The ability of the one-dimensional and CFD models
to predict the performance of the PDEC and solar chimney were investigated.
The results indicated that an inlet configuration called a TFI (Turbine Fan
Inlet) performed the best at the tested wind speeds. The TFI was further able
to significantly increase volumetric flow rate in the PDEC shaft for the dry
evaporative cartridge tests. The outlet that performed best under the tests is
a Windmaster Tornado Wind Turbine, or Whirlybird, which is a commercially
available configuration.
The one-dimensional models were not able to accurately predict conditions
during start-up. The CFD models were highly accurate in predicting the experimental values. It is recommended that a two-dimensional theoretical
model be developed to better predict start-up conditions. / AFRIKAANSE OPSOMMING: Verhoogde bewustheid van omgewings probleme het belangstelling in hernubare
energie stelsels ontwaak. Natuurlike ventilasie stelsels is veral van belang,
sedert mense die meeste van hul tyd binnenshuis spandeer. Binnenshuise lug
kwaliteit is ’n belangrike oorweging wanneer menslike gesondheid en insittendes
se gemak in stand gehou moet word.
Hierdie studie fokus op die bepaling van die beste inlaat en uitlaat vorm
van ’n gekose stel konfigurasies vir ’n natuurlike ventilasie-stelsel. Die inlaaten
uitlaat-konfigurasies is op ’n PDEC (Passive Downdraught Evaporative
Cooling) skag en sonkrag skoorsteen getoets. Die PDEC het ’n verdampings
doek, gemaak van katoen, ingesluit. Onafhanklike modelle van die PDEC en
sonkrag skoorsteen is in ’n termies-beheerde ruimte en die konfigurasies is by
’n onveranderende wind spoed getoets. Die konfigurasies is op ’n nat of droog
PDEC skag en op ’n warm of koue son skoorsteen getoets.
Een-dimensionele eindige verskil modelle, wat sommige twee-dimensionele
effekte in ag neem in die verdampings doek, van die doek en sonkrag skoorsteen
is ontwikkel. CFD (Computational Fluid Dynamics) modelle is verder
gebou in FLUENTr, wat die werkstoestande vir elke inlaat en uitlaat toets
simuleer. Die CFD modelle is ontwikkel om die eksperimentele data met numeriese
waardes te vergelyk. Die vermoë van die een-dimensionele en CFD
modelle om die verrigting van die PDEC en sonkrag skoorsteen te voorspel, is
ondersoek.
Die resultate dui daarop dat ’n inlaat opset genoem TFI (Turbine Fan
Inlet) die beste vaar by die elke getoetsde wind spoed. Die TFI was verder in
staat om die volumetriese vloeitempo in die PDEC skag aansienlik te verhoog
vir die toetse met ’n droë verdamping doek. Die uitlaat wat die beste presteer het in die toetse is ’n Windmaster Tornado Wind Turbine, of Whirlybird, wat
’n kommersieel beskikbare konfigurasie is.
Die een-dimensionele modelle was nie in staat om die toestande tydens die
begin-fase akkuraat te voorspel nie. Die CFD modelle was hoogs akkuraat in
die voorspelling van die eksperimentele waardes. Dit word aanbeveel dat ’n
twee-dimensionele teoretiese model ontwikkel word om die toestande tydens
begin-fase beter te voorspel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97110 |
| Date | 03 1900 |
| Creators | Swiegers, Jacobus Johannes |
| Contributors | Dobson, Robert Thomas, Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 150 pages : illustrations, maps |
| Rights | Stellenbosch University |
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