[article]
| Titre : |
New instrument for measuring water vapor flux density from arbitrary surfaces |
| Type de document : |
texte imprimé |
| Auteurs : |
R. E. Imhof, Auteur ; E. P. Berg, Auteur ; Robert P. Chilcott, Auteur ; L. I. Ciortea, Auteur ; Flavius C. Pascut, Auteur ; P. Xiao, Auteur |
| Année de publication : |
2002 |
| Article en page(s) : |
p. 297-301 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Catégories : |
Couche cornée
Perméabilité
Transpiration
Vapeur d'eau
|
| Tags : |
'Perte d'eau transépidermique' 'Flux de vapeur d'eau' 'Perméabilité du stratum corneum' TEWL à la surface peau' |
| Index. décimale : |
668.5 Parfums et cosmétiques |
| Résumé : |
We report the development of a new instrument, the AquaFlux, for measuring water vapor flux density from arbitrary surfaces, including in-vivo measurements of transepidermal water loss (TEWL), skin surface water loss (SSWL) and perspiration. It uses a closed measurements chamber equipped with an electronically cooled condenser, to maintain a precisely reproducible microclimate adjacent to the test surface under all ambient conditions. The condenser creates a diffusion vapor density gradient, from which the flux density can be measured. We explore the properties of the AquaFlux by means of a mathematical model, which was also adapted for calculating comparable properties of open-chamber instruments. In this way, we found the intrinsic sensitivity of the AquaFlux to be approximately 40% higher than that of an open-chamber instrument. However, in an experimental comparison of volar forearm TEWL measurements between the AquaFlux and an open-chamber Evaporimeter, we found a tenfold difference in coefficient of variation. We attribute the much lower than predicted sensitivity of the Evaporimeter to extrinsic noise from diffusion zone instability induced by ambient air movements. The mathematical model was also used to calculate the relative humidity immediately above the test surface, where we found values that generally differed from ambient values in both instrument types. The effect of this on TEWL measurements is discussed in detail. It is concluded that, during the relatively short time of measurements, such microclimate changes affect mainly the transient SSWL component rather than the underlying TEWL. Finally, the model was used to estimate the flux density that would cause the relative humidity at the test surface to reach 100%. This sets an upper limit to the flux densities that can be measured and may be a cause of instrument non-linearity at high flux densities, as microclimate saturation is approached. |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10632 |
in IFSCC MAGAZINE > Vol. 5, N° 4 (10-11-12/2002) . - p. 297-301
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