An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting
Water droplets on eight different enhanced surfaces were experimentally investigated to determine the droplet impact behaviors and their effects on the cooling performances of these enhanced surfaces. The surfaces were fabricated using selective laser melting (SLM), which is an Additive Manufacturin...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
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2018
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| Online Access: | https://hdl.handle.net/10356/87739 http://hdl.handle.net/10220/45477 |
| _version_ | 1811687923911753728 |
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| author | Wang, X.W. Ho, Jin Yao Leong, Kai Choong |
| author2 | School of Mechanical and Aerospace Engineering |
| author_facet | School of Mechanical and Aerospace Engineering Wang, X.W. Ho, Jin Yao Leong, Kai Choong |
| author_sort | Wang, X.W. |
| collection | NTU |
| description | Water droplets on eight different enhanced surfaces were experimentally investigated to determine the droplet impact behaviors and their effects on the cooling performances of these enhanced surfaces. The surfaces were fabricated using selective laser melting (SLM), which is an Additive Manufacturing (AM) technique that uses a high power-density laser to melt and fuse metallic powders together. In the experiments, the surface material is an aluminum alloy (AlSi10Mg) and the liquid is water. The droplet diameter was maintained at 2.4 mm, impact Weber numbers of 28, 122 and 202 were used and the droplet frequencies ranged from 0.79 Hz to 3.97 Hz. These surfaces, which were heated above the Leidenfrost temperature, were investigated at incidence angles of 90° and 45° and their results were compared against a smooth surface. Using high speed imaging, the evolutions of droplet dynamics on the heated surfaces were determined and the effects of the droplets’ behavior on the cooling performances of the enhanced surfaces were elucidated. Our results showed that fin density played an important role in the droplet dynamics. When the fin density was high, the integrity of the droplet can be maintained after impact. On the other hand, increasing the fin height can usually improve the droplet heat transfer on clavate fin surface. For the Low density and the Globe surfaces (cylindrical + clavate), the droplets could be trapped on the fin surfaces which enhanced cooling. A combination of film boiling and nucleate boiling was observed on the Low density, the Clavate fins and the Globe fin surfaces. From transient cooling curves obtained for the various surfaces, it was determined that the Globe, High clavate and Low density surfaces demonstrated significantly better cooling performances as compared to the other enhanced and smooth surfaces. The best cooling performance was achieved with the Globe surface at We=121, f=3.97 and θ=90°. |
| first_indexed | 2024-10-01T05:24:02Z |
| format | Journal Article |
| id | ntu-10356/87739 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T05:24:02Z |
| publishDate | 2018 |
| record_format | dspace |
| spelling | ntu-10356/877392023-03-04T17:16:28Z An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting Wang, X.W. Ho, Jin Yao Leong, Kai Choong School of Mechanical and Aerospace Engineering Singapore Centre for 3D Printing Leidenfrost Point Film Boiling Water droplets on eight different enhanced surfaces were experimentally investigated to determine the droplet impact behaviors and their effects on the cooling performances of these enhanced surfaces. The surfaces were fabricated using selective laser melting (SLM), which is an Additive Manufacturing (AM) technique that uses a high power-density laser to melt and fuse metallic powders together. In the experiments, the surface material is an aluminum alloy (AlSi10Mg) and the liquid is water. The droplet diameter was maintained at 2.4 mm, impact Weber numbers of 28, 122 and 202 were used and the droplet frequencies ranged from 0.79 Hz to 3.97 Hz. These surfaces, which were heated above the Leidenfrost temperature, were investigated at incidence angles of 90° and 45° and their results were compared against a smooth surface. Using high speed imaging, the evolutions of droplet dynamics on the heated surfaces were determined and the effects of the droplets’ behavior on the cooling performances of the enhanced surfaces were elucidated. Our results showed that fin density played an important role in the droplet dynamics. When the fin density was high, the integrity of the droplet can be maintained after impact. On the other hand, increasing the fin height can usually improve the droplet heat transfer on clavate fin surface. For the Low density and the Globe surfaces (cylindrical + clavate), the droplets could be trapped on the fin surfaces which enhanced cooling. A combination of film boiling and nucleate boiling was observed on the Low density, the Clavate fins and the Globe fin surfaces. From transient cooling curves obtained for the various surfaces, it was determined that the Globe, High clavate and Low density surfaces demonstrated significantly better cooling performances as compared to the other enhanced and smooth surfaces. The best cooling performance was achieved with the Globe surface at We=121, f=3.97 and θ=90°. NRF (Natl Research Foundation, S’pore) Accepted version 2018-08-06T07:11:03Z 2019-12-06T16:48:23Z 2018-08-06T07:11:03Z 2019-12-06T16:48:23Z 2018 Journal Article Wang, X., Ho, J., & Leong, K. (2018). An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting. International Journal of Heat and Mass Transfer, 120, 652-670. 0017-9310 https://hdl.handle.net/10356/87739 http://hdl.handle.net/10220/45477 10.1016/j.ijheatmasstransfer.2017.12.033 en International Journal of Heat and Mass Transfer © 2017 Elsevier Ltd. This is the author created version of a work that has been peer reviewed and accepted for publication by International Journal of Heat and Mass Transfer, Elsevier Ltd. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1016/j.ijheatmasstransfer.2017.12.033]. 27 p. application/pdf |
| spellingShingle | Leidenfrost Point Film Boiling Wang, X.W. Ho, Jin Yao Leong, Kai Choong An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title | An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title_full | An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title_fullStr | An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title_full_unstemmed | An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title_short | An experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| title_sort | experimental investigation of single droplet impact cooling on hot enhanced surfaces fabricated by selective laser melting |
| topic | Leidenfrost Point Film Boiling |
| url | https://hdl.handle.net/10356/87739 http://hdl.handle.net/10220/45477 |
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