Design of an environment controlled dew tracking setup to emphasize the role of the relative humidity on breath figures dynamics

Nicolas Pionnier,Solmaz Boroomandi Barati,Rémi Berger,Stéphane Valette,Matthieu Guibert,Stéphane Benayoun,Elise Contraires

doi:10.1140/epjti/s40485-018-0043-3

Abstract

In polymer protection pieces, polycarbonate is often used for its transparency and its high impact resistance. However, when dew appears it degrades light transmission and thus transparency. To solve this problem, anti-fogging surfaces are developed.To further understand the dew formation in natural environment in order to design high efficiency anti-fogging surfaces on polycarbonate, a recently designed dew tracking setup giving dew pictures and a digital imaging procedure allowing reliable and highly accurate droplet measurements were developed. Thanks to this setup, dew formation conditions such as relative humidity level and air temperature can be chosen and studied. Particular attention is paid to the evolution of the number of droplets according to the relative humidity and how it explains the droplet growth rate. The influence of the relative humidity (RH) on the growth rate of non-coalescing dropwise condensation has already been observed. This paper is based on these existing results as a comparison to validate the experimental setup and the post-processing analysis. We shall also use the number of droplets to further explain the role of the RH on condensation dynamics.Moreover, by applying a light subcooling, the growth kinetics were slowed down in order to observe every characteristic phase in detail and even particular intermediate phases.Graphical Breath figures observation via the dew tracking setup

Highlights

Dew is the condensation on cold surfaces of water vapor present in a humid environment
Particular attention is paid to the evolution of the number of droplets according to the relative humidity and how it explains the droplet growth rate
We shall use the number of droplets to further explain the role of the relative humidity (RH) on condensation dynamics

Summary

Introduction

Dew is the condensation on cold surfaces of water vapor present in a humid environment. Some authors have suggested the use of this phenomenon for water harvesting, improving power plant vapor condensation efficiency or other applied systems [1,2,3,4,5]. These solutions were designed for getting high heat transfer fluxes, increasing the liquid water condensation rate. To limit the presence of droplets, anti-fogging surfaces are designed by Pionnier et al EPJ Techniques and Instrumentation (2018) 5:2 modifying the wettability properties [7, 9, 10]. Two approaches exist - reducing the presence of water on surfaces (hydrophobic surface treatments) or spreading droplets to create a uniform water film (hydrophilic surface treatments) [11, 12]

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