Vapour cooling of poorly conducting hot substrates increases the dynamic Leidenfrost temperature
| Autor: | Detlef Lohse, Pascal Sleutel, Minori Shirota, Michiel A. J. van Limbeek, Chao Sun, Andrea Prosperetti |
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| Přispěvatelé: | Physics of Fluids, Faculty of Science and Technology |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Materials science
Non-isothermal transient heat-transfer Meteorology 02 engineering and technology Drop impact 01 natural sciences Leidenfrost effect METIS-316071 Isothermal process 010305 fluids & plasmas Boiling 0103 physical sciences High-speed TIR imaging Spray cooling Fluid Flow and Transfer Processes Drop (liquid) Mechanical Engineering Mechanics 021001 nanoscience & nanotechnology Condensed Matter Physics Thermal time scale Heat transfer Wetting 0210 nano-technology IR-99591 |
| Zdroj: | International journal of heat and mass transfer, 97, 101-109. Elsevier |
| ISSN: | 0017-9310 |
| DOI: | 10.1016/j.ijheatmasstransfer.2016.01.080 |
| Popis: | A drop impacting a smooth solid surface heated above the saturation temperature can either touch it (contact boiling) or not (film boiling), depending on the surface temperature. The heat transfer is greatly reduced in the latter case by the insulating vapour layer under the drop. In contrast to previous studies, here we use a relatively poor thermally conducting glass surface. Using a total internal reflection method, we visualise the wetting dynamics of the drop on the surface. We discover a new touch-down process, in which liquid–solid contact occurs a few hundred microseconds after the initial impact. This phenomenon is due to the cooling of the solid surface by the generation of vapour. We propose a model to account for this cooling effect, and validate it experimentally with our observations. The model leads to the determination of a thermal time scale (about 0.3ms for glass) for the cooling of the solid. We conclude that when the impact time scale of the drop on the substrate (drop diameter/impact velocity) is of the order of the thermal time scale or larger, the cooling effect cannot be neglected and the drop will make contact in this manner. If the impact time scale however is much smaller than the thermal time scale, the surface remains essentially isothermal and the impact dynamics is not affected. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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