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Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger.
Thesis (PhD)--Stellenbosch University, 2018.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2018
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| _version_ | 1867613921690517504 |
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| access_status_str | Open Access |
| author | Engelbrecht, Ruan Aldrich |
| author2 | Meyer, Chris J. |
| author_browse | Engelbrecht, Ruan Aldrich Meyer, Chris J. |
| author_facet | Meyer, Chris J. Engelbrecht, Ruan Aldrich |
| author_sort | Engelbrecht, Ruan Aldrich |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2018. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/105082 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:50.076Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/105082 Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. Engelbrecht, Ruan Aldrich Meyer, Chris J. Van der Spuy, S. J. Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. UCTD Heat exchangers Fans (Machinery) -- Performance Numerical analysis Fans (Machinery) -- Valuation Thesis (PhD)--Stellenbosch University, 2018. ENGLISH ABSTRACT: This study aims to develop an accurate and reliable numerical model of an Air-Cooled Condenser (ACC) using Computational Fluid Dynamics (CFD). Simplified methods for modelling the axial ow fan and heat exchanger are used to limit the complexity of the computations. The actuator disk and extended actuator disk model is presented and validated using two fans with different physical characteristics. The A-fan is an axial flow fan commonly used in industrial cooling applications and the B2a-fan is an axial ow fan developed at Stellenbosch University. The heat exchanger model is based on the A-frame heat exchanger typically used in ACCs. Validation is performed with respect to heat exchanger mechanical losses and heat transfer. The operating point of each combined fan and heat exchanger unit is determined analytically and numerically under ideal operating conditions. The results are validated by comparing the kinetic energy recovery coeficient to an experimental design from literature. A numerical recovery coeficient of 0.527 was measured compared to 0.553 measured experimentally. The axial ow fan, heat exchanger and ACC model are successfully validated. A 30 fan ACC bank in a 6x5 configuration is analysed with regard to performance under cross-wind conditions using three different fan configurations. The ACC is subjected to four different wind speeds along five directions. Comparisons are drawn between the volumetric, thermal and overall performance using the heat-to-power ratio. The so-called A-fan ACC, B2a-fan ACC and Combined ACC are considered. Major findings indicate that the performance of an ACC decreases with increasing cross-wind speed. Superior overall performance is measured for the B2a-fan ACC resulting from a 19 % increase in performance to the A-fans on the upstream periphery. Higher thermal performance is also measured as well as 6-10 % lower power consumption than the A-fan ACC and Combined ACC. The A-fan ACC exhibits the highest sensitivity to increasing cross-wind speeds along with the highest power consumption. Heat-to-power performance is measured 9-10 % lower than the B2a-fan ACC and 7 % lower than the Combined ACC as a result. A comparative study between the 6x5 and 3x10 ACC layout is also presented. Wind directions leads to volumetric, thermal and overall performance differences up to 23 % for the A-fan ACC in 3x10 layout for a constant wind speed. The 6x5 layout measured differences up to 5 %. The 3x10 layout is therefore considered to exhibit a higher sensitivity to wind direction. This is attributed to the asymmetrical nature of the configuration. The A-fan ACC in 3x10 layout consumes 9.70 % more power compared to the 6x5 layout. The B2a-fan ACC consumes 6.95 % more power with similar power consumption measured for the Combined ACC. An on-site measurement methodology for determining the fan volumetric ow rate using the measured fan power consumption and resultant blade loading along with the characteristic curves to determine the flow rate is presented. This is discussed, analysed and applied to the 30 fan ACC under cross-wind conditions. Differences in predicted volumetric ow rate up to 6.45 %, measured to the numerical results, are noted for fans not subjected to distorted inflow. Predictions for upstream periphery fans shows poor correlation with differences up to 22.81 % measured. The results do indicate that the use of the blade loading for fans subject to distorted in flow gives more accurate results for flow rate predictions compared to the power consumption. AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om 'n akkurate en betroubare numeriese model van 'n lugverkoelde kondensor (LVK) te ontwikkel deur gebruik te maak van berekeningsvloeimeganika (BVM). Die kompleksiteit van die berekeninge word verminder deur vereenvoudigde metodes vir die modellering van die aksiaalwaaier en hitteruiler te gebruik. Die aksieskyfmodel en die verlengde aksieskyfmodel word aangebied en bevestig met behulp van twee waaiers, elkeen met verskillende fisiese eienskappe. Die sogenaamde A-waaier is 'n aksiaalwaaier wat gebruik word in industriële verkoelingstoepassings, en die B2a-waaier is 'n aksiaalwaaier wat ontwerp en vervaardig is by Stellenbosch Universiteit. 'n Model vir 'n A-raam hitteruiler, wat tipies in LVKs gebruik word, word ontwikkel en bevestig met betrekking tot die hitteruiler meganiese verliese asook die hitte-oordrag. Die werkspunt van elke gekombineerde waaier en hitteruiler eenheid word analities en numeries bepaal in ideale bedryfsomstandighede. Die resultate word bevestig deur gebruik te maak van die kinetiese energie herstel koëffisiënt van 'n eksperimentele ontwerp uit die literatuur. 'n Numeriese herstel koëffisiënt van 0.527 is gemeet in vergelyking met die eksperimentele resultaat van 0.553. Die aksiaalwaaier, hitteruiler en LVK model word suksesvol bevestig. 'n LVK bank van 30 waaiers met 'n 6x5 konfigurasie word geanaliseer met betrekking tot die werkverrigting in wind toestande deur gebruik te maak van drie verskillende waaierkonfigurasies. Die LVK word blootgestel aan vier verskillende windsnelhede en vyf windrigtings. Verglykings word getrek tussen die volumetriese, termiese en algehele werkverrigtinge in die vorm van die hitte-tot-krag verhouding. Die sogenaamde A-waaier LVK, B2a-waaier LVK en die Gekombineerde LVK word oorweeg. Bevindinge dui daarop dat die werkverrigting van 'n LVK afneem met toenemende windsnelheid. Ho er algehele werkverrigting word waargeneem met die B2a-waaier LVK as gevolg van 'n 19 % verhoging in stroom-op periferie waaier werkverrigting in verglyking met die A-waaier. Hoër termiese werkverrigting word ook gemeet, asook 'n 6-10 % laer kragverbruik in verglyking met die A-waaier LVK en Gekombineerde LVK. Die A-waaier LVK vertoon die hoogste sensitiwiteit vir toeneemende windsnelhede tesame met die hoogste kragverbruik. Hitte-tot-krag werkverrigting word 9-10 % laer gemeet as die B2a-waaier LVK en 7 % laer as die Gekombineerde LVK. 'n Vergelykende studie word ook aangebied tussen die 6x5 en 3x10 LVK uitleg. Windrigting lei tot volumetriese, termiese en algehele werkverrigting verskille van 23 % vir die A-waaier LVK met 'n 3x10 uitleg vir 'n konstante windspoed. Die 6x5 uitleg toon verskille van 5 % aan. Soortgelyke termiese en algehele werkverrigting uktuasies word opgemerk. Die 3x10 uitleg vertoon dus 'n hoër sensitiwiteit aan vir windrigting wat aan die asimmetriese aard van die konfigurasie toegeskryf word. Die A-waaier LVK met 'n 3x10 uitleg verbruik 9.70 % meer krag as die 6x5 uitleg. Die B2a-waaier LVK verbruik 6.95 % meer krag met soortgelyke kragverbruiking gemeet vir die Gekombineerde LVK met die 3x10 uitleg as die 6x5 uitleg. 'n Metingsmetodiek word aangebied om die volumetriese vloeitempo van die waaier te bepaal deur gebruik te maak van die waaier kragverbruiking en lembelasting saam met die karakteristieke kurwes. Hierdie word bespreek, geanaliseer en toegepas op die 30 waaier LVK bank in kruiswindtoestande. Volumetriese vloeitempo voorspelling verskille tot 6.45 % in vergelyking met die numeriese resultate word waargeneem vir waaiers wat nie aan inlaat vloeiversteuring kondisies blootgestel is nie. Voorspelling vir stroom-op periferie waaiers wys swak korrelasie met verskille tot 22.81 % gemeet. Die resulte dui daarop dat die lembelasting vloeitempo meer akkuraat voorspel vir waaiers wat aan inlaat vloeiversteurings blootgestel word in vergelyking met die kragverbruiking. Doctoral 2018-11-27T21:38:54Z 2018-12-07T06:58:39Z 2018-11-27T21:38:54Z 2018-12-07T06:58:39Z 2018-12 Thesis http://hdl.handle.net/10019.1/105082 en_ZA Stellenbosch University 200 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | UCTD Heat exchangers Fans (Machinery) -- Performance Numerical analysis Fans (Machinery) -- Valuation Engelbrecht, Ruan Aldrich Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title | Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title_full | Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title_fullStr | Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title_full_unstemmed | Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title_short | Numerical Investigation of fan performance in a forced-draft air-cooled heat exchanger. |
| title_sort | numerical investigation of fan performance in a forced draft air cooled heat exchanger |
| topic | UCTD Heat exchangers Fans (Machinery) -- Performance Numerical analysis Fans (Machinery) -- Valuation |
| url | http://hdl.handle.net/10019.1/105082 |
| work_keys_str_mv | AT engelbrechtruanaldrich numericalinvestigationoffanperformanceinaforceddraftaircooledheatexchanger |