A numerical investigation of air-cooled steam condenser performance under windy conditions

Owen, Michael Trevor Foxwell (2010-03)

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.

Thesis

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.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/4101
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