Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses
One of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unans...
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| Format: | Article |
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MDPI AG
2020-12-01
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| Series: | Energies |
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| Online Access: | https://www.mdpi.com/1996-1073/14/1/105 |
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| author | Tomasz Kura Jan Wajs Elzbieta Fornalik-Wajs Sasa Kenjeres Sebastian Gurgul |
| author_facet | Tomasz Kura Jan Wajs Elzbieta Fornalik-Wajs Sasa Kenjeres Sebastian Gurgul |
| author_sort | Tomasz Kura |
| collection | DOAJ |
| description | One of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical analysis is still very challenging. The authors’ aim was to construct the numerical model which can represent the real phenomena with good or very good accuracy. Starting with an analysis of single jet and obtaining the agreement with experimental data, it will be possible to extend the model towards the whole minijets heat exchanger. The OpenFOAM software, Bracknell, UK was used for that purpose, with our own implementation of the <i>ζ</i>-<i>f</i> turbulence model. The most difficult area to model is the stagnation region, where the thermal effects are the most intensive and, at the same time, strongly affected by the conditions in the pipe/nozzle/orifice of various size (conventional, mini, micro), from which the jet is injected. In the following article, summary of authors’ findings, regarding significance of the velocity profile and turbulence intensity at the jet place of discharge are presented. In addition, qualitative analysis of the heat transfer enhancement is included, in relation to the inlet conditions. In the stagnation point, Nusselt number differences reached the 10%, while, in general, its discrepancy in relation to inlet conditions was up to 23%. |
| first_indexed | 2024-03-10T13:44:59Z |
| format | Article |
| id | doaj.art-de2ed6b64f444ba38c26e1c07876c7fb |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-10T13:44:59Z |
| publishDate | 2020-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-de2ed6b64f444ba38c26e1c07876c7fb2023-11-21T02:46:10ZengMDPI AGEnergies1996-10732020-12-0114110510.3390/en14010105Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical AnalysesTomasz Kura0Jan Wajs1Elzbieta Fornalik-Wajs2Sasa Kenjeres3Sebastian Gurgul4Department of Fundamental Research in Energy Engineering, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, PolandDepartment of Energy and Industrial Apparatus, Faculty of Mechanical Engineering, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, PolandDepartment of Fundamental Research in Energy Engineering, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, PolandDepartment of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The NetherlandsDepartment of Fundamental Research in Energy Engineering, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, PolandOne of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical analysis is still very challenging. The authors’ aim was to construct the numerical model which can represent the real phenomena with good or very good accuracy. Starting with an analysis of single jet and obtaining the agreement with experimental data, it will be possible to extend the model towards the whole minijets heat exchanger. The OpenFOAM software, Bracknell, UK was used for that purpose, with our own implementation of the <i>ζ</i>-<i>f</i> turbulence model. The most difficult area to model is the stagnation region, where the thermal effects are the most intensive and, at the same time, strongly affected by the conditions in the pipe/nozzle/orifice of various size (conventional, mini, micro), from which the jet is injected. In the following article, summary of authors’ findings, regarding significance of the velocity profile and turbulence intensity at the jet place of discharge are presented. In addition, qualitative analysis of the heat transfer enhancement is included, in relation to the inlet conditions. In the stagnation point, Nusselt number differences reached the 10%, while, in general, its discrepancy in relation to inlet conditions was up to 23%.https://www.mdpi.com/1996-1073/14/1/105jet impingementheat transfer enhancementturbulence characteristics<i>ζ</i>-<i>f</i> RANS modelOpenFoam |
| spellingShingle | Tomasz Kura Jan Wajs Elzbieta Fornalik-Wajs Sasa Kenjeres Sebastian Gurgul Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses Energies jet impingement heat transfer enhancement turbulence characteristics <i>ζ</i>-<i>f</i> RANS model OpenFoam |
| title | Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses |
| title_full | Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses |
| title_fullStr | Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses |
| title_full_unstemmed | Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses |
| title_short | Thermal and Hydrodynamic Phenomena in the Stagnation Zone—Impact of the Inlet Turbulence Characteristics on the Numerical Analyses |
| title_sort | thermal and hydrodynamic phenomena in the stagnation zone impact of the inlet turbulence characteristics on the numerical analyses |
| topic | jet impingement heat transfer enhancement turbulence characteristics <i>ζ</i>-<i>f</i> RANS model OpenFoam |
| url | https://www.mdpi.com/1996-1073/14/1/105 |
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