Combined three-color LIF-PDA measurements and infrared thermography applied to the study of the spray impingement on a heated surface above the Leidenfrost regime

Abstract : This experimental study deals with the impingement of sprays on a heated wall in close to semi-industrial conditions. Therefore, an experimental set-up was specifically designed: high liquid mass flux (up to 8 kg/m2/s), large droplets (up to 300 μm) and high surface temperature widely above the Leidenfrost point (up to 800 °C). The surface to be cooled is a 175 mm diameter nickel disk with 5 mm thickness heated by electromagnetic induction. The spraying devices consist in full cone sprays. Several studies, performed under these particular conditions, has allowed characterizing the heat flux removed by the spray by using techniques based on thermocouples or infrared thermography (IRT). However, to investigate more finely the heat transfer mechanism, it is necessary to measure the droplet temperature but, to date, no measurement for sprays are available in the literature. Therefore, the objective of the present work is to demonstrate the ability of the three-color Laser Induced Fluorescence (3cLIF) to meet this challenge. The combination of the 3cLIF with a Phase Doppler system allows also determining the droplet temperature per size class before and after impact. By adding the IRT measurements combined to an inverse heat conduction model, an energy balance is done in order to estimate the evaporated liquid mass. The influence of the normal Weber number on the liquid vaporization is investigated by using three sprays (Normal Weber numbers up to about 1500). Thereby, main results show that the droplets temperature after impact increases with the incident Weber number before to reach a plateau, attributed to the apparition of the splashing regime. The analysis of the energy balance shows that the mass of evaporated liquid decreases with the incident Weber number and the droplet heating. These first results are in well agreement with previous works conducted with single calibrated droplets, validating as the same time the use of combined 3cLIF-PDA measurements in the case of sprays.
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Communication dans un congrès
18th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Jul 2016, Lisbonne, Portugal. 104, pp.1008 - 1021, 2017, International Journal of Heat and Mass Transfer. 〈10.1016/j.ijheatmasstransfer.2016.07.029〉
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https://hal.univ-lorraine.fr/hal-01445616
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Soumis le : mercredi 25 janvier 2017 - 10:44:01
Dernière modification le : jeudi 11 janvier 2018 - 06:27:33

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Alexandre Labergue, Juan-David Pena-Carillo, Michel Gradeck, Fabrice Lemoine. Combined three-color LIF-PDA measurements and infrared thermography applied to the study of the spray impingement on a heated surface above the Leidenfrost regime. 18th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Jul 2016, Lisbonne, Portugal. 104, pp.1008 - 1021, 2017, International Journal of Heat and Mass Transfer. 〈10.1016/j.ijheatmasstransfer.2016.07.029〉. 〈hal-01445616〉

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