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Approche expérimentale de la ventilation par déplacement

Abstract : Every heat source set in a fluid is responsible for buoyancy forces. By entraining ambient air, these forces produce a plume which may transport a passive contaminant. In a room where such sources are present, the principle of displacement ventilation is to supply fresh air in the lower part of a room. A vertical stratification appears showing a clean lower zone and a warmer and poliuted upper zone where a recirculation flow occurs. Similarity conditions, based on convective heat transfer, allowed us to define an hydraulic model of a configuration of a typical industrial room. Thermal natural convection flows were simulated by mass transfer phenomena and pure axisymmetric buoyant plumes were produced inside the model. These plumes were characterised by velo city measurements using Laser Doppler Anemometry. An experimental technique based on digital processing of images obtained from Laser Induced Fluorescence was developed to measure concentration. The light fluid injected at the source was marked with a fluorescent tracer in order to study the interface zone, where two fluids of different densities mix. The increase in thickness of this interface was observed. Finally, this work focused on the variation of the stratification height as a function of ventilation flow rate and of several source parameters. The measurements allowed us to distinguish two zones. Far above the source, the stratification height is correctly described by a form used for volume flux in a fully developed plume. To describe the stratification height when it is close to the elevation of the source (at a distance shorter than a source diameter), a form using the ventilation volume flow rate, the initial buoyancy flux and the characteristic dimension of the source was proposed.
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Submitted on : Thursday, March 29, 2018 - 10:37:16 AM
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  • HAL Id : tel-01746415, version 1



Olivier Auban. Approche expérimentale de la ventilation par déplacement. Autre. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10003⟩. ⟨tel-01746415⟩



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