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Conference Papers Year : 2017

Instantaneous heat transfers at the impact of a droplet onto a hot surfaces in the film boiling regime

Abstract

Heat and mass transfers at the impact of a droplet onto a hot solid surface are investigated experimentally. Millimeter- sized water droplets impinges onto a perfectly flat sapphire surface heated at 600°C. The temperature of the liquid inside the droplet is measured using the two-color laser-induced fluorescence (2cLIF) technique. Water is seeded with a temperature-sensitive fluorescent dye, while a nanosecond pulsed laser is used for the excitation of the fluo- rescence. The ratio of fluorescence signal detected in two appropriate spectral bands allows to determine the liquid temperature. One advantage of this non-intrusive optical technique is that it eliminates adverse effects associated with signal variations caused by droplet shape during its impact. In parallel, the temperature of the solid surface is characterized using infrared thermography. The latter measurements are made possible by the deposition of a nanosize coating of titanium aluminium nitride (TiAlN) on the upper surface of the sapphire window. Thanks to the high frame rate of the IR camera, the time evolution of the heat flux distribution at the solid surface can be recon- structed. A comparison of IR and 2cLIF techniques enable to correlate the heating of the liquid with the cooling of the wall. This reveals that most of the heat removed from the solid surface is devoted to the heating of the liquid, the energy used for liquid vaporization being significantly lower.
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Dates and versions

hal-01740921 , version 1 (22-03-2018)

Licence

Attribution - NonCommercial - NoDerivatives

Identifiers

  • HAL Id : hal-01740921 , version 1

Cite

William Chaze, Guillaume Castanet, Ophelie Caballina, Denis Maillet, Jean-François Pierson, et al.. Instantaneous heat transfers at the impact of a droplet onto a hot surfaces in the film boiling regime. 28th Conference on Liquid Atomization and Spray Systems, Sep 2017, Valencia, Spain. ⟨hal-01740921⟩
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