Performance comparison of forced draft and induced draft air-cooled condensers under adverse Crosswind Conditions.
| dc.contributor.advisor | Meyer, C. J. | en_ZA |
| dc.contributor.advisor | Van der Spuy, S. J. | en_ZA |
| dc.contributor.author | Louw, D. L. | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-11-30T20:31:19Z | |
| dc.date.accessioned | 2021-12-22T14:25:43Z | |
| dc.date.available | 2021-11-30T20:31:19Z | |
| dc.date.available | 2021-12-22T14:25:43Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: n this study numerical models of two 8×8 fan-unit Air-Cooled Condensers (ACCs) were developed using Computational Fluid Dynamics (CFD). The two ACCs investigated were respectively a Forced Draft ACC with A-frame fan- units and an Induced Draft ACC with V-frame fan-units. The performance of the two ACCs was investigated under various adverse crosswind conditions. The numerical models were implemented using the open-source OpenFOAM CFD code and solved in parallel using a computer cluster. The ACCs’ axial flow fans were modeled using an Actuator Disk Model (ADM). The ACCs investigated in this study were configured using two dif- ferent axial flow fans: an eight bladed fan identified as the L-fan, and a nine bladed fan identfied as the N-fan. Comparatively the L-fan has a steeper pressure characteristic and a higher power consumption than the N-fan and was used exclusively at the front and back periphery of the ACCs. The ADM was specifically implemented for the two fans and succesfully validated against experimental results obtained from a BS 848 Type A Facility. A direct comparison of the two ACCs shows that under normal operating conditions the Induced Draft ACC outperforms the Forced Draft ACC both with regards to its volumetric effectiveness and heat transfer effectiveness. The two ACC were then subjected to crosswinds of 3, 6 and 9 m/s from two different directions: primary crosswinds where the L-fan is used at the leading edge, and secondary crosswinds where the N-fan is used at the leading edge. The Forced Draft ACC showed a greater reduction in axial flow fan per- formance under crosswind conditions than the Induced Draft ACC. Under primary crosswinds the L-fan equipped leading edge fan-units were able to mitigate the reduced fan performance better than the N-fan equiped leading edge fan-units under secondary crosswinds. The Induced Draft ACC showed higher heat exchanger inlet air temper- atures under crosswind conditions than the Forced Draft ACC. The Induced Draft ACC’s perpendicular orientation of its V-frame fan-units to secondary crosswinds allowed for greater increases in the inlet air temperatures at its downwind fan-units’ heat exchangers. The Induced Draft ACC’s heat transfer rate to fan power consumption ratio under primary crosswind conditions was higher than that of the Forced Draft ACC under either primary or secondary crosswinds. In contrast the Induced Draft ACC’s heat-to-power ratio under secondary crosswind conditions was worse than that of the Forced Draft ACC under either primary or secondary crosswinds. The mean heat-to-power ratio of the Induced Draft ACC under normal operating conditions was higher than that of the Forced Draft ACC with a ratio of 120.6 W/W compared to 99.4 W/W. However, the mean heat-to- power ratio of the Induced Draft ACC decreased more by 23.3% and 35.6% under 9 m/s primary and secondary crosswinds, while the heat-to-power ratios of the Forced Draft ACC decreased less by 10.8% and 15.4% under the same crosswinds. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: n hierdie studie is numeriese modelle van twee 8 × 8 waaiereenheid lugver- koelde kondensors (LVKs) met behulp van numeriese vloei meganika ontwik- kel. Die twee LVKs was onderskeidelik ’n Geforseerde Vloei LVK met A-raam waaiereenhede en ’n Geïnduseerde Vloei LVK met V-raam waaiereenhede. Die werksverrigting van die twee LVKs onder verskeie wind toestande is in hier- die studie ondersoek en vergelyk. Die numeriese modelle was ontwikkel met behulp van die OpenFOAM vloeimeganika kode en geïmplementeer vir parallel oplossing op ’n trosrekenaar. Die LVKs se aksiaalvloei waaiers is met ’n aksieskyfmodel gemodelleer. Die twee LVKs is met twee verskillende aksiaalvloei waaiers opgestel: ’n agt-lem waaier en ’n nege lem waaier wat onderskeidelik die L-waaier en die N-waaier genoem is. Die L-waaier het vergelykbaar ’n steiler druk karakteristiek en hoër kragverbruik as die N-waaier en is uitsluitlik by die voorkant en agterkant van die LVKs gebruik. Die aksieskyfmodel was spesifiek vir die studie geïmplen- teer en is suksesvol gevalideer teenoor eksperimentele resultate van ’n BS 848 Tipe A Fasiliteit. ’n Direkte vergelyking van die twee LVKs wys dat sonder enige wind die Geïnduseerde Vloei LVK meer doeltreffend is as die Geforseerde Vloei LVK met betrekking tot beide die volumetriese effektiwiteit en die hitte oordrag effektiwiteit. Die twee LVK se werksverrigting is daarna onder kruiswinde van 3, 6 en 9 m/s vanaf twee verskillende windsrigtings getoets: waar die primêre windsrigting die L-waaier by die voorkant van die LVK plaas, en waar sekondêre winde die N-waaier by die voorkant van die LVK plaas. Die Geforseerde Vloei LVK wys ’n laer vermindering in die waaier effekti- witeit onder kruiswinde as die Geïnduseerde Vloei LVK. Onder primêre kruis- winde wys die L-waaier waaiereenhede aan die voorkant van die LVK ’n laer vermindering in waaier effectiwiteit as die N-waaier waaiereenhede aan die sykant van die LVK onder sekondêre kruiswinde. Die Geïnduseerde Vloei LVK wys a groter verhoging in die hitte-uitruilers se lug inlaat temperatuur onder kruiswinde as die Geforseerde Vloei LVK. Die Geïnduseerde Vloei LVK se loodregte opstelling van sy V-raam hitte- uitruilers teenoor die sekondêre kruiswind het groter verhogings in die lug inlaat temperature van stroomaf waaiereenhede se hitte-uitruilers veroorsaak. Die Geïnduseerde Vloei LVK se hitte oordragstempo teenoor die waaiers se kragverbruik onder primêre kruiswinde was hoër as die van die Geforseerde Vloei LVK onder beide primêre en sekondêre kruiswinde. In kontras was die Geïnduseerde Vloei LVK se hitte-to-kragverbruiks verhouding onder sekondêre kruiswinde laer as die van die Geforseerde Vloei LVK onder beide primêre en sekondêre kruiswinde. Die gemiddelde hitteoordrag-tot-kragverbruik verhouding van die Geïndu- seerde Vloei LVK onder normale toestande was hoër as dit van die Geforseerde Vloei LVK met ’n verhouding van 120.6 W/W teenoor 99.4 W/W. Die gemid- delde hitteoordrag-tot-kragverbruik verhouding van die Geïnduseerde Vloei LVK het met 23.3% en 35.6% verminder onder 9 m/s primêre en sekondêre kruiswinde, terwyl die Geforseerde Vloei LVK slegs met 10.8% en 15.4% ver- minder het onder dieselfde kruiswind toestande. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | 169 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/123862 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Air-cooled condensers | en_ZA |
| dc.subject | Computational fluid dynamics | en_ZA |
| dc.subject | Actuators -- Disc model | en_ZA |
| dc.subject | Crosswinds | en_ZA |
| dc.subject | Axial flow -- Fans (Machinery) | en_ZA |
| dc.title | Performance comparison of forced draft and induced draft air-cooled condensers under adverse Crosswind Conditions. | en_ZA |
| dc.type | Thesis | en_ZA |