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Refroidissement radiatif et texturation de surfaces pour condenseurs de rosée à haut rendement

Abstract : This work is a contribution to the development of passive condensation and dew water harvesting. In the first part, we report a study on rough surfaces developed by a simple surface treatment (sand-blasting). Results obtained show that roughness of surface favors droplet shedding compared to the original smooth substrate, provided that sand-blasting does not increase too much the surface roughness. This process enhances the density of nucleation sites and the coalescences events at a sub-micron scale, thus lowering the lag-time to obtain drop sliding during condensation. Experiments show that combining sand-blasting and edge effects can thus increase substantially the passive collection by gravity from a substrate. Gains about 30% when compared to the same smooth substrate are obtained. In a second part, a laboratory radiative chamber is developed, which carries out radiative exchanges between a centimeter-sized object and a cold source. This device makes it possible to study the radiative properties of different materials on the performance of passive dew condensers. In a humid environment, condensation is obtained on objects of various geometries, including geometries for which contact cooling is very inefficient. An important result was obtained with the device : the beginning of the condensation process is highly dependent on the emissivity of the surface; but it is no longer so when the surface is covered with water drops. A simplified model of radiative exchanges between a water drops on a planar surface and its environment is proposed to establish an expression for the average emissivity of a surface covered with condensed water drops.
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Submitted on : Thursday, November 12, 2020 - 12:11:21 PM
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  • HAL Id : tel-03001267, version 1

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Joachim Trosseille. Refroidissement radiatif et texturation de surfaces pour condenseurs de rosée à haut rendement. Thermique [physics.class-ph]. Sorbonne Université, 2019. Français. ⟨NNT : 2019SORUS383⟩. ⟨tel-03001267⟩

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