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Temporally resolved PLIF measurements of the temperature inside droplets impinging on a hot solid surface

Abstract : Heat transfers at the impact of a droplet on a hot solid surface are investigated experimentally. Millimeter-sized droplets impinge a heated flat sapphire window. The time evolution of the droplet temperature is characterized using the two-color laser-induced fluorescence technique. For that, a Q-switched Nd:YAG laser is used for the excitation of the fluorescence in order to obtain instantaneous images of the droplet temperature. The fluid under investigation is seeded with two fluorescent dyes, one sensitive to temperature (fluorescein disodium) and the other not (sulforhodamine 640). Owing to a wavelength shift between the dyes' emissions, the fluorescence signal of the dyes can be detected separately by two cameras. The liquid temperature is determined with a good accuracy by doing the ratio of the images of the dyes' fluorescence. A critical feature of the method is that the image ratio is not disturbed by the deformation of the impacting droplet, which affects the signals of the dyes almost identically. Experiments are performed in the conditions of film boiling. A thin vapor film at the interface between the droplet and the solid surface prevents the deposition of liquid on the hot solid surface. Results highlight how the temperature distribution inside a droplet evolves when it impinges on a heated solid surface in the film boiling regime. By changing the impact velocity for water and ethanol droplets, comparisons between several experimental cases show the effect of the Weber number and of the fluid properties on the heat transfers within the droplet during its interaction with the heated surface.
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Contributor : Ophélie Caballina <>
Submitted on : Wednesday, August 29, 2018 - 10:45:58 AM
Last modification on : Monday, March 29, 2021 - 4:03:13 PM
Long-term archiving on: : Friday, November 30, 2018 - 1:13:26 PM


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  • HAL Id : hal-01863893, version 1



William Chaze, Romain Collignon, Ophélie Caballina, Guillaume Castanet, Fabrice Lemoine. Temporally resolved PLIF measurements of the temperature inside droplets impinging on a hot solid surface. 19th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Jul 2018, Lisbon, Portugal. ⟨hal-01863893⟩



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