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Numerical optimisation and theoretical analysis of complex microchannel heat exchangers
The purpose of this study is to evaluate the performance of the geometries in forced convective heat transfer and steady state laminar incompressible fluid flow. Microchannel heat sinks used were numerically modelled from highly conductive (aluminium) solid material substrate. ANSYS FLUENT Response...
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| Format: | Thesis |
| Language: | English English |
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Department of Mechanical Engineering
2025
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| _version_ | 1867613344271171584 |
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| access_status_str | Open Access |
| author | Godi, Nahum Yustus |
| author2 | Collier-Reed, Brandon |
| author_browse | Collier-Reed, Brandon Godi, Nahum Yustus |
| author_facet | Collier-Reed, Brandon Godi, Nahum Yustus |
| author_sort | Godi, Nahum Yustus |
| collection | Thesis |
| description | The purpose of this study is to evaluate the performance of the geometries in forced convective heat transfer and steady state laminar incompressible fluid flow. Microchannel heat sinks used were numerically modelled from highly conductive (aluminium) solid material substrate. ANSYS FLUENT Response Surface Optimisation Tool (RSO) was used to numerically optimise and compare the performance of combined microchannel heat sinks with perforated, solid, half-hollow and hollow fins. The simulation began by optimising a typical microchannel heat sink geometry before fin-bars were inserted into the cooling channel to augment heat transfer. Furthermore, solid and perforated fins were modelled and added on the top of the typical heat sink. The performance of the various configurations was then compared. A novel combined microchannel design with circular micro fins was modelled with a circular flow channel. Additionally, a hybrid model was developed, incorporating circular fins on a microchannel heat sink with a rectangular flow channel. The third design featured rectangular fins mounted on a microchannel with a rectangular flow channel. The combined microchannels, featuring circular and rectangular fins, were cooled by water flowing through the channels and internally along the fin inner surface walls to dissipate heat. These designs were then integrated into the computational domain and subjected to cooling using both water and an air stream. The water flows through the flow channel while air flows over the vertical fins to remove excess heat from the external wall surfaces of the fins in forced convection laminar flow condition. Theoretical analysis (intersection of asymptotes method) was carried out in the cooling channels (circular and rectangular). The theoretical analysis results indicated the presence of an optimal geometry among the various cross-sectional shapes, effectively cooling a volume with a uniformly distributed heat flux. A comparison of the analytic findings with the numerical results demonstrates that an optimal design is possible. The numerical cooling processes were carried out in parallel and counter flows. These findings demonstrate that an optimal design can be realised with a combination of Computational Fluid Dynamics and geometric modelling techniques. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/42213 |
| institution | University of Cape Town (South Africa) |
| language | English eng |
| last_indexed | 2026-06-10T12:34:39.078Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Department of Mechanical Engineering |
| publisherStr | Department of Mechanical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/42213 Numerical optimisation and theoretical analysis of complex microchannel heat exchangers Godi, Nahum Yustus Collier-Reed, Brandon Ngoepe, Malebogo thermal conductance complex heat exchangers small length scale microchannel heat sink micro complex fins computational fluid dynamics geometric optimisation optimal design heat sink global volume and manufacturing constraints The purpose of this study is to evaluate the performance of the geometries in forced convective heat transfer and steady state laminar incompressible fluid flow. Microchannel heat sinks used were numerically modelled from highly conductive (aluminium) solid material substrate. ANSYS FLUENT Response Surface Optimisation Tool (RSO) was used to numerically optimise and compare the performance of combined microchannel heat sinks with perforated, solid, half-hollow and hollow fins. The simulation began by optimising a typical microchannel heat sink geometry before fin-bars were inserted into the cooling channel to augment heat transfer. Furthermore, solid and perforated fins were modelled and added on the top of the typical heat sink. The performance of the various configurations was then compared. A novel combined microchannel design with circular micro fins was modelled with a circular flow channel. Additionally, a hybrid model was developed, incorporating circular fins on a microchannel heat sink with a rectangular flow channel. The third design featured rectangular fins mounted on a microchannel with a rectangular flow channel. The combined microchannels, featuring circular and rectangular fins, were cooled by water flowing through the channels and internally along the fin inner surface walls to dissipate heat. These designs were then integrated into the computational domain and subjected to cooling using both water and an air stream. The water flows through the flow channel while air flows over the vertical fins to remove excess heat from the external wall surfaces of the fins in forced convection laminar flow condition. Theoretical analysis (intersection of asymptotes method) was carried out in the cooling channels (circular and rectangular). The theoretical analysis results indicated the presence of an optimal geometry among the various cross-sectional shapes, effectively cooling a volume with a uniformly distributed heat flux. A comparison of the analytic findings with the numerical results demonstrates that an optimal design is possible. The numerical cooling processes were carried out in parallel and counter flows. These findings demonstrate that an optimal design can be realised with a combination of Computational Fluid Dynamics and geometric modelling techniques. 2025-11-13T09:51:44Z 2025-11-13T09:51:44Z 2025 2025-11-13T07:01:11Z Thesis / Dissertation Doctoral PhD http://hdl.handle.net/11427/42213 en eng application/pdf Department of Mechanical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | thermal conductance complex heat exchangers small length scale microchannel heat sink micro complex fins computational fluid dynamics geometric optimisation optimal design heat sink global volume and manufacturing constraints Godi, Nahum Yustus Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| thesis_degree_str | Doctoral |
| title | Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| title_full | Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| title_fullStr | Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| title_full_unstemmed | Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| title_short | Numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| title_sort | numerical optimisation and theoretical analysis of complex microchannel heat exchangers |
| topic | thermal conductance complex heat exchangers small length scale microchannel heat sink micro complex fins computational fluid dynamics geometric optimisation optimal design heat sink global volume and manufacturing constraints |
| url | http://hdl.handle.net/11427/42213 |
| work_keys_str_mv | AT godinahumyustus numericaloptimisationandtheoreticalanalysisofcomplexmicrochannelheatexchangers |