scholarly journals Photothermal Techniques Applied to the Determination of the Water Vapor Diffusion Coefficient and Thermal Diffusivity of Edible Films

2007 ◽  
Vol 23 (4) ◽  
pp. 457-461 ◽  
Author(s):  
M. A. AGUILAR-MENDEZ ◽  
E. San MARTIN-MARTINEZ ◽  
J. E. MORALES ◽  
A. CRUZ-OREA ◽  
M. R. JAIME-FONSECA
Keyword(s):  
Diffusion Coefficient ◽  
Water Vapor ◽  
Thermal Diffusivity ◽  
Edible Films ◽  
Photothermal Techniques ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion

scholarly journals Macroscopic water vapor diffusion is not enhanced in snow

2020 ◽  
Author(s):  
Kévin Fourteau ◽  
Florent Domine ◽  
Pascal Hagenmuller
Keyword(s):  
Diffusion Coefficient ◽  
Water Vapor ◽  
Effective Diffusion Coefficient ◽  
Molecular Diffusion ◽  
Pore Space ◽  
Effective Diffusion ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion

Abstract. Water vapor transport in dry snowpacks plays a significant role for snow metamorphism and the mass and energy balance of snowpacks. The molecular diffusion of water vapor in the interstitial pores is usually considered as the main or only transport mechanism, and current detailed snow physics models therefore rely on the knowledge of the effective diffusion coefficient of water vapor in snow. Numerous previous studies have concluded that water vapor diffusion in snow is enhanced relative to that in air. Various field observations also indicate that for vapor transport in snow to be explained by diffusion alone, the effective diffusion coefficient should be larger than that in air. Here we show using theory and numerical simulations on idealized and measured snow microstructures that, although sublimation and condensation of water vapor onto snow crystal surfaces do enhance microscopic diffusion in the pore space, this effect is more than countered by the restriction of diffusion space due to ice. The interaction of water vapor with the ice results in water vapor diffusing more than inert molecules in snow, but still less than in free air, regardless of the value of the accommodation coefficient of water on ice. Our results imply that processes other than diffusion, probably convection, play a preponderant role in water vapor transport in dry snowpacks.

WATER VAPOR TRANSPORT IN PLASTERS CONTAINING SUPERABSORBENT POLYMERS

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Jan Fořt ◽  
Martin Mildner ◽  
Petr Hotěk ◽  
Robert Černý
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Transport Properties ◽  
Building Design ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Diffusion Resistance ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion

A proper characterization of material properties represents an important step towards an efficient building design. Considering the present issues in the construction sector, moisture loads pose a risk not only to increased material deterioration but also to the health of building inhabitants. In this paper, modified plaster mixtures with superabsorbent admixture are designed in order to improve passive moderation of finishing layers against varying humidity conditions. The relationship between the amount of applied superabsorbent admixture and resulting water vapor transport properties is identified and the influence of temperature on water vapor transport is analyzed. The steady-state cup method is used for the determination of water vapor transport properties, namely the water vapor diffusion permeability, water vapor diffusion coefficient and water vapor diffusion resistance factor. The obtained data show temperature as a very significant factor affecting water vapor transport in the analyzed plasters. Considering the dry-cup method arrangement, relative humidity probes should be used for monitoring relative humidity under the sealed sample for a sufficiently precise determination of water vapor pressure gradient.

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