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Forced draught supercritical carbon dioxide cooling system performance
Boshoff, F. D. 2025. Forced draught supercritical carbon dioxide cooling system performance. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/4368ce76-3ec7-455e-97c5-c717e04f7215
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| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613847696703488 |
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| access_status_str | Open Access |
| author | Boshoff, Francois Daneel |
| author2 | Van der Spuy, Johan |
| author_browse | Boshoff, Francois Daneel Van der Spuy, Johan |
| author_facet | Van der Spuy, Johan Boshoff, Francois Daneel |
| author_sort | Boshoff, Francois Daneel |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Boshoff, F. D. 2025. Forced draught supercritical carbon dioxide cooling system performance. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/4368ce76-3ec7-455e-97c5-c717e04f7215 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132115 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:38.497Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132115 Forced draught supercritical carbon dioxide cooling system performance Boshoff, Francois Daneel Van der Spuy, Johan Pretorius, Johannes Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. Cooling systems Thermodynamic cycles Computational fluid dynamics Heat exchangers -- Thermodynamics Axial flow UCTD Boshoff, F. D. 2025. Forced draught supercritical carbon dioxide cooling system performance. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/4368ce76-3ec7-455e-97c5-c717e04f7215 Thesis (PhD)--Stellenbosch University, 2025. ENGLISH ABSTRACT: An axial flow fan was designed for an air-cooled heat exchanger (ACHE) unit of a concentrated solar power plant, which makes use of a supercritical carbon dioxide (sCO2) Brayton cycle. The ACHE’s geometry and cooling requirements are used to derive the fan specifications. This results in an unusual axial flow fan design, with a hub-to-tip ratio of 0.51 and low blade twist. The fan was simulated using computational fluid dynamics (CFD), by means of a periodic three dimensional model (P3DM). Fan performance is evaluated in two different domains: an annulus upstream and downstream of the fan blade, and a domain representing an ISO 5801 Type A fan test facility. The P3DM is used to demonstrate the effect of tip gap size, hub configuration and scaling on performance. A 1:4.78 scale fan was manufactured and experimentally tested in an ISO 5801 Type A facility. The experimental and simulated performance show good agreement at all tip gap sizes and flow rates simulated. After correcting for blade modifications during manufacturing, the experimental design fan static pressure, shaft power and static efficiency values are 1.8 Pa (1.8%) lower, 0.013 kW (0.9%) higher, and 1.7% (3.2%) lower than the corresponding P3DM results. The fan and ACHE interaction was investigated using an isothermal CFD simulation, which models the bundle using a Porous Media Model. The operating point agrees well with analytical results, with a difference of only 0.9 m3/s (0.5%), being 6.3 m3/s (3.6%) below the design flow rate. A range of plenum heights and an extended annulus configuration are tested. The results indicate that plenum heights of 0.3 to 0.5 times the fan casing diameter facilitates the highest flow rates, whereas longer plenums improve the velocity profile’s uniformity. The extended annulus configuration is shown to improve both the flow rate and velocity profile uniformity. To investigate the integrated ACHE’s thermal behaviour, a co-simulation model was developed which simultaneously solves the air flow field using three-dimensional CFD, and the sCO2 flow field using a one-dimensional network method. The air-side model is validated through comparison with the isothermal model, while the sCO2 model is validated through comparison with results from literature. The co-simulation predicts a higher heat exchanger pressure drop than the isothermal model, resulting in the flow rate being 18.5 m3/s (10.5%) below the design value. The overall heat transfer rate is also found to be 21.5 MW (20.5%) below the intended value. The results indicate that the sCO2 in tubes directly downstream of the fan blades are cooled to a slightly lower temperature than the sCO2 in the other tubes. However, due to the overall heat transfer rate being lower than intended, the outlet conditions are still well above the critical point. AFRIKAANSE OPSOMMING: ’n Aksiaalwaaier is ontwerp vir ’n lugverkoelde warmteruiler (LVWR) eenheid in ’n gekonsentreerde sonkrag aanleg, gebaseer op ’n super-kritiese koolstofdioksied (sCO2) Brayton-siklus. Die LVWR geometrie en verkoelingvereistes word gebruik om waaierspesifikasies af te lei, wat lei tot ’n ongewone waaierontwerp met ’n naafhuls verhouding van 0.51, en ’n lemhoek wat min wissel tussen die naaf en huls. Die waaier is gesimuleer met berekeningsvloeimeganika (BVM), deur middel van ’n periodiese drie-dimensionele model (P3DM). Waaierverrigting is bepaal vir twee uitlegte: ’n waaier met ’n annulus stroomop en stroomaf, en ’n waaier binne ’n ISO 5801 Tipe A toetsfasiliteit. Die P3DM word gebruik om die effek van puntgapinggrootte, waaierkonfigurasies en skalering op verrigting te demonstreer. ’n 1:4.78-skaalwaaier is vervaardig en gebruik om die waaierverrigting te bepaal in ’n ISO 5801 Tipe A waaier-toetsfasiliteit. Die eksperimentele en ge-simuleerde resultate stem goed ooreen by alle puntgapinggroottes en vloeitempos wat gesimuleer word. Nadat veranderinge aan die lem gedurende vervaardiging in ag geneem is, is die eksperimentele waaier se statiese druk, as-drywing en statiese benuttingsgraad by die ontwerpspunt 1.8 Pa (1.8%) laer, 0.013 kW (0.9%) hoër en 1.7% (3.2%) laer in vergelyking met die ooreenstemmende P3DM resultate. Die waaier en LVWR interaksie is ondersoek met ’n isotermiese BVM simulasie, wat die warmteruilerbundel vereenvoudig met ’n Poreuse Media Model. Die werkspunt verskil slegs met 0.9 m3/s (0.5%) teenoor ’n analitiese oplossing, en is 6.3 m3/s (3.6%) onder die ontwerpswaarde. Verskeie plenumhoogtes en ’n verlengdeannulus konfigurasie is getoets, wat wys dat plenumhoogtes van 0.3 tot 0.5 maal die waaierdeursnee die hoogste vloeitempo’s produseer, terwyl langer plenums meer uniforme snelheidsprofiele voorsien. Die verlengde-annulus konfigurasie verskaf beide ’n verbeterde vloeitempo asook ’n meer uniforme snelheidsprofiel. Om die geïntegreerde LVWR se termiese gedrag te ondersoek is ’n mede- simulasiemodel ontwikkel, wat terselfdetyd die lugvloei oplos met drie-dimensionele BVM, en die sCO2 vloei oplos met ’n een-dimensionele netwerk metode. Die lugmodel word gevalideer deur vergelyking met die isotermiese model, en die sCO2- model deur vergelyking met resultate uit die literatuur. Die medesimulasie voorspel ’n hoër drukval deur die warmteruiler as die isotermiese model, met ’n lugvloeitempo wat verminder tot 18.5 m3/s (10.5%) onder die ontwerpswaarde. Daar word gevind dat die algehele warmteoordragtempo 21.5 MW (20.5%) onder die ontwerpspunt is. Die resultate wys dat sCO2 in buise direk agter die waaierlemme tot effe laer temperature verkoel word as sCO2 in ander buise. Aangesien die algehele warmteoordragtempo laer is as die ontwerpswaarde, bly die uitlaattoestande egter ver bo die kritiese punt. Doctoral 2025-05-26T05:48:59Z 2025-05-26T05:48:59Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132115 en Stellenbosch University xx, 179 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Cooling systems Thermodynamic cycles Computational fluid dynamics Heat exchangers -- Thermodynamics Axial flow UCTD Boshoff, Francois Daneel Forced draught supercritical carbon dioxide cooling system performance |
| title | Forced draught supercritical carbon dioxide cooling system performance |
| title_full | Forced draught supercritical carbon dioxide cooling system performance |
| title_fullStr | Forced draught supercritical carbon dioxide cooling system performance |
| title_full_unstemmed | Forced draught supercritical carbon dioxide cooling system performance |
| title_short | Forced draught supercritical carbon dioxide cooling system performance |
| title_sort | forced draught supercritical carbon dioxide cooling system performance |
| topic | Cooling systems Thermodynamic cycles Computational fluid dynamics Heat exchangers -- Thermodynamics Axial flow UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132115 |
| work_keys_str_mv | AT boshofffrancoisdaneel forceddraughtsupercriticalcarbondioxidecoolingsystemperformance |