Etude de l'influence de l'injection sur l'aérothermique de jets en impact

Abstract : In the context of an impinging jet, nozzle geometry markedly impacts heat transfer between jet and plate by affecting the velocity profile at the jet exit and thereby potentially modifying the behavior of the jet's vortex structures. Moreover, even if Reynolds number is the main influence criterion of a jet, the injection diameter can play on heat transfer through compressibility effects. Our work bas therefore focused on aerodynamic and thermal experimental study of impinging air jets. Particle image velocimetry (PIV) was used for velocity measurements. For thermal measurements, a method based on the simultaneous use of a heating film and the infrared thermography was used. Aerodynamic results are used to explain the observed thermal phenomena. The first part allowed us to study and compare six different injection geometries : round orifice, cross-shaped orifice and daisy orifice, perforated on fiat and hemispherical surface with the same free area. The results show that the hemispherical surface leads to better heat transfer than the flat surface, but the effect decreases progressively with jet-to-plate distance increasing.The round injection on hemisphere brings the best heat transfer in comparison with the other injections. The second part allowed us to examine the compressibility effect of impinging air jets (for Mach numbers up to 0.9). The results show that the effect of the compressibility on Nusselt number is limited to the stagnation region.
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Xuan Thao Trinh. Etude de l'influence de l'injection sur l'aérothermique de jets en impact. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2015. Français. ⟨NNT : 2015ESMA0016⟩. ⟨tel-01276250⟩

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