EPJ Techn Instrum (2018) 5: 2
https://doi.org/10.1140/epjti/s40485-018-0043-3

Research article

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

¹ Université de Lyon, Ecole Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513, F-69131, 36 Avenue Guy de Collongue, Ecully, France
² PSA Peugeot Citroën, Vélizy-Villacoublay, E78943, France
³ Université de Lyon, Ecole Nationale Supérieure des Mines de Saint-Etienne, LGF, UMR 5307, 158 Cours Fauriel, Saint-Etienne, France

^* e-mail: nicolas.pionnier@doctorant.ec-lyon.fr
^** e-mail: stephane.valette@ec-lyon.fr

Received: 2 May 2017
Accepted: 29 January 2018
Published online: 17 February 2018

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 Abstract

Breath figures observation via the dew tracking setup