Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This study is aimed at the development of an efficient and reliable method of evaluating the
performance of an air-cooled steam condenser (ACSC) under windy conditions, using
computational fluid dynamics (CFD). A two-step modelling approach is employed as a result
of computational limitations. The numerical ACSC model developed in this study makes use
of the pressure jump fan model, amongst other approximations, in an attempt to minimize the
computational expense of the performance evaluation. The accuracy of the numerical model
is verified through a comparison of the numerical results to test data collected during full
scale tests carried out on an operational ACSC. Good correlation is achieved between the
numerical results and test data. Further verification is carried out through a comparison to
previous numerical work. Satisfactory convergence is achieved for the most part and the few
discrepancies in the results are explained. The effect of wind on ACSC performance at El
Dorado Power Plant (Nevada, USA) is investigated and it is found that reduced fan
performance due to distorted flow at the inlet of the upstream fans is the primary contributor
to the reduction in performance associated with increased wind speed in this case. An attempt
is subsequently made to identify effective wind effect mitigation measures. To this end the
effects of wind screens, solid walkways and increasing the fan power are investigated. It is
found that the installation of an appropriate wind screen configuration provides a useful
means of reducing the negative effects of wind on ACSC performance and an improved wind
screen configuration is suggested for El Dorado. Solid walkways are also shown to be
beneficial to ACSC performance under windy conditions. It is further found that ACSC
performance increases with walkway width but that the installation of excessively wide
walkways is not justifiable. Finally, increasing the fan power during periods of unfavourable
ambient conditions is shown to have limited benefit in this case. The model developed in this
study has the potential to allow for the evaluation of large ACSC installations and provides a
reliable platform from which further investigations into improving ACSC performance under
windy conditions can be carried out. / AFRIKAANSE OPSOMMING: Hierdie studie is daarop gemik om die ontwikkeling van 'n geskikte en betroubare metode
van evaluering van die verrigting van ’n lugverkoelde stoom-kondensator (air-cooled steam
condenser, ACSC) onder winderige toestande, met behulp van numeriese vloei-dinamika. ’n
Twee-stap modelleringsbenadering is aangewend as gevolg van rekenaar beperkings. Die
numeriese ACSC-model wat in hierdie studie ontwikkel is, maak gebruik van die druksprong
waaier model, asook ander benaderings, in ’n poging om die berekeningskoste van die
verrigting-evaluering te verminder. Die akkuraatheid van die numeriese model is bevestig
deur middel van ’n vergelyking van die numeriese resultate met toetsdata ingesamel tydens
die volskaal toetse uitgevoer op ’n operasionele ACSC. Goeie korrelasie is bereik tussen die
numeriese resultate en toetsdata. Verdere bevestiging is uitgevoer deur middel van ’n
vergelyking met vorige numeriese werk. Bevredigende konvergensie is in die algemeen
bereik en die paar verskille in die resultate word verduidelik. Die effek van wind op ACSC
verrigting by El Dorado Power Plant (Nevada, VSA) is ondersoek, en daar is bevind dat
verlaagde waaierverrigting, as gevolg van vervormde vloei by die inlaat van die stroomop
waaiers, die primêre bydraer is tot die afname in ACSC werkverrigting geassosieer met
verhoogde windsnelheid in hierdie geval. ’n Poging word dan aangewend om effektiewe
wind-effek velagingsmaatreëls te identifiseer. Windskerms, soliede wandelvlakke en die
verhoging van die waaierkrag word gevolglik ondersoek. Daar is bevind dat die installasie
van ’n toepaslike windskerm-opset ’n nuttige middel tot ’n vermindering van die negatiewe
effekte van wind op ACSC verrigting bied, en ’n verbeterde windskerm opset is voorgestel
vir El Dorado. Soliede wandelvlakke word ook aanbeveel as voordelig vir ACSC verrigting
onder winderige toestande. Dit is verder bevind dat die ACSC prestasie verhoog met
wandelvlak breedte, maar dat die installasie van ’n te ruim wandelvlak nie regverdigbaar is
nie. Ten slotte, word bewys dat die verhoging van die waaierkrag tydens periodes van
ongunstige omgewingsomstandighede ’n beperkte voordeel in hierdie geval het. Die model
wat ontwikkel is in hierdie studie het die potensiaal om voorsiening te maak vir die
evaluering van groot ACSC- installasies en bied ’n betroubare platform vanwaar verdere
ondersoeke tot die verbetering van ACSC verrigting onder winderige toestande uitgevoer kan
word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4101 |
| Date | 03 1900 |
| Creators | Owen, Michael Trevor Foxwell |
| Contributors | Kroger, D. G., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 102 p. : ill. |
| Rights | University of Stellenbosch |
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