Optimisation towards a wind resistant air-cooled condenser for the modern energy sector.
| dc.contributor.advisor | Owen, Michael | en_ZA |
| dc.contributor.advisor | Muiyser, Jacques | en_ZA |
| dc.contributor.author | Marincowitz, F. S. | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-11-30T20:37:41Z | |
| dc.date.accessioned | 2021-12-22T14:25:40Z | |
| dc.date.available | 2021-11-30T20:37:41Z | |
| dc.date.available | 2021-12-22T14:25:40Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Past research has shown that wind negatively affects the thermal performance of an air-cooled condenser (ACC) and increases dynamic fan blade loading. Several different wind-effect mitigation measures have been investigated, including cruci- form screens, perimeter screens, walkways, deflector plates, alternative fan rota- tional speeds or blade angles and different module array configurations. However, these investigations were performed using different ACC configurations, consider- ing mainly ACC thermal performance as an evaluation metric and mostly neglecting dynamic fan blade loading. This study investigated three promising externally in- stalled wind-effect mitigation mechanisms (cruciform screens, perimeter screens and walkways) with the aim of identifying general guidelines on how these miti- gation measures could be optimally combined to improve the thermal performance and reduce dynamic fan blade loading. The study focuses on ACCs for the modern energy sector in which smaller solar thermal and natural gas combined cycle power plants are largely replacing large fossil-fuelled plants. A 3 × 6-cell ACC, typical of ∼ 100 MW plants, was therefore selected for investigation. An efficient computational fluid dynamics-based numerical ACC model, incorpo- rating the extended actuator disk fan model, was developed for this investigation. A multi-objective optimisation was performed using a genetic algorithm combined with a meta-modelling approach to identify optimal wind-mitigation solutions for two realistic wind distributions. This was done to identify generalised optimum so- lutions that improve ACC thermal performance and reduce dynamic blade loading in windy conditions, without causing a hindrance in calm conditions. The optimal solutions from these two demonstrative examples provided the required information to identify general guidelines for wind-effect mitigation on the ACC in question. The combination of a cruciform screen and a walkway is always recommended. The cruciform screen should have a height of 0.35 ≤ Hcs/Hp ≤ 0.50 and a solid- ity of 0.75 ≤ αcs ≤ 1.0. The width of the walkway should be within the range 0.30 ≤ Lww/d f ≤ 0.50. A perimeter screen is only recommended if dynamic blade loading is expected to be a significant issue, or is still an issue after installing the combination of cruciform screen and walkway. If a non-retractable perimeter screen is considered, the solidity of this screen should be αps ≈ 0.4, with a screen height of between 0.6 ≤ Hps/Hp ≤ 1.0. However, a retractable screen is an attractive option, as such a screen can be deployed only at higher wind speeds (vw > 6 m/s). In the case of a retractable screen, a larger solidity screen of 0.5 ≤ αps ≤ 0.6 spanning the full length of the ACC (Hps/Hp = 1.0) should be used to most effectively reduce dynamic blade loading for short periods of time. It was shown that, for a wind- effect mitigation measure solution that falls within these ranges, an improvement in the ACC’s average thermal effectiveness of up to 19% is possible for a high wind speed condition, while also reducing the blade loading by 22%. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Vorige navorsing het getoon dat wind die hitte-uitruilingvermoë van ’n lugverkoelde kondensors (LVKs) negatief beïnvloed asook die dinamiese belasting van die waai- erlemme verhoog. Verskeie wind-effek versagtingsmaatreëls is in die verlede on- dersoek, dit sluit kruisskerms, randskerms, loopvlakke, defleksieplate, alternatiewe waaiersnelhede of lemhoeke en verskillende module-konfigurasies. Hierdie on- dersoeke was egter met verskillende LVK -konfigurasies uitgevoer, met hoofsaak- lik hitte uitruiling as ’n evaluerings maatstaf, terwyl die dinamiese lembelasting meestal geïgnoreer was. In hierdie studie is drie belowende ekstern geïnstalleerde meganismes vir windeffekversagting ondersoek (kruisskerms, randskerms en loop- vlakke) met die doel om algemene riglyne te identifiseer oor hoe hierdie versag- tingsmaatreëls optimaal gekombineer kan word om die LVK se hitte uitruiling ver- moë te verbeter en om die dinamiese lembelasting te verminder. Die studie fokus op LVKs vir die moderne energiesektor, waar kleiner termiese sonkrag en natuurlike gas kragaanlegte die groot fossiel-aangedrewe aanlegte vervang. ’n LVK met 3 × 6 selle, wat tipies is van ’n ∼ 100 MW kragaanleg, is gekies vir ondersoek. ’n Effektiewe berekeningsvloeimeganika-gebaseerde numeriese LVK-model, wat die verlengde aksieskyfmodel insluit, was ontwikkel vir hierdie ondersoek. ’n Multi-objektiewe optimering is uitgevoer met behulp van ’n genetiese algoritme gekombineer met ’n meta-modellerings benadering is uitgevoer om optimale wind- versagtingsoplossings vir twee realistiese windverspreidings te identifiseer. Die was uitgevoer om algemene optimale oplossings te identifiseer wat die LVK se werkver- rigting in winderige toestande sal verbeter, sonder om ’n belemmering by windlose toestande te veroorsaak. Die optimale oplossings uit hierdie twee voorbeelde het die nodige inligting verskaf om die algemene riglyne vir die vermindering van win- deffekte op die betrokke LVK te identifiseer. ’n Kruisskerm in kombinasie met ’n loopvlak word altyd aanbeveel. Die kruisskerm moet ’n hoogte van 0.35 ≤ Hcs/Hp ≤ 0.50 en ’n soliditeit van 0.75 ≤ αcs ≤ 1.0 hê. Die breedte van die loopvlak moet tussen 0.30 ≤ Lww/d f ≤ 0.50 wees. ’n Rand- skerm word slegs aanbeveel as verhoogte lembelasting ’n kwessie is, of as dit steeds probleme veroorsaak nadat die kombinasie van ’n kruisskerm en loopvlak geïnstal- leer is. As ’n nie-intrekbare randskerm in ag geneem word, moet die soliditeit van hierdie skerm αps ≈ 0.4 wees, met ’n skermhoogte tussen 0.6 ≤ Hps/Hp ≤ 1.0. ’n Intrekbare skerm is egter ’n goeie opsie, aangesien so ’n skerm slegs ontplooi hoef te word as die windspoed hoog is (vw > 6 m/s). As ’n intrekbare skerm gebruik word, moet die skermsoliditeit hoër wees (0.5 ≤ αps ≤ 0.6) en oor die volle hoogte van die LVK span (Hps/Hp = 1.0) om die effektiefste uitwerking op die dinamiese lembelading te hê. Daar is getoon dat vir ’n wind-effek versagtingsmaatreël oplos- sing wat binne hierdie reekse val, ’n verbetering in die LVK se gemiddelde termiese doeltreffendheid van tot 19% moontlik is vir ’n hoë windspoed toestand, terwyl dit ook die lembelansing met 22% verminder. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/123861 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Capacitors | en_ZA |
| dc.subject | Wind mitigation | en_ZA |
| dc.subject | Dynamic loading (Materials) | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Renewable energy sources | en_ZA |
| dc.subject | Air-cooled condenser | en_ZA |
| dc.subject | Wind resistant -- Measures | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Optimisation towards a wind resistant air-cooled condenser for the modern energy sector. | en_ZA |
| dc.type | Thesis | en_ZA |