Effect of Test Methods on Apparent Moisture Vapour Transmission of P/V and P/C Fabrics

2014 ◽  
Vol 18 (1) ◽  
pp. 71-79
Author(s):  
Subhasis Das ◽  
V. K. Kothari
Keyword(s):  
Water Vapour ◽  
Transmission Rate ◽  
Test Methods ◽  
Test Method ◽  
Transport Rate ◽  
Vapour Transport ◽  
Vapour Permeability ◽  
Water Vapour Transport ◽  
Moisture Vapour

The moisture vapour permeability properties of a series of almost similar polyesterviscose (P/V) and polyester-cotton (P/C) blended fabrics are investigated. The water vapour transport rate greatly differs depending on the principle of the test methods, even when other parameters are nearly identical, such as air permeability, areal density, porosity and thickness. The water absorption characteristics of fibre seem to be the most important in determining the overall water vapour transport rate. Substitution of polyester for viscose and cotton in P/V and P/C blended fabrics respectively, reduces the water transport rate of the fabrics in a long term method. It is found that the P/C blended fabrics show greater water vapour transport than the corresponding P/V fabrics when a long term test method is used; however, the P/V fabrics show relatively higher water vapour permeability than the P/C fabrics when short duration tests are carried out by using the Permetest and moisture vapour transmission rate (MVTR) cell methods

Poleward moisture transport and its influence on precipitation in the Arctic: From case studies to long-term statistics

2020 ◽  
Author(s):  
Melanie Lauer ◽  
Annette Rinke ◽  
Irina Gorodetskaya ◽  
Susanne Crewell
Keyword(s):  
Sea Ice ◽  
Case Studies ◽  
Water Vapour ◽  
Moisture Transport ◽  
Longwave Radiation ◽  
The Arctic ◽  
Vapour Transport ◽  
Water Vapour Transport ◽  
Downward Longwave Radiation

<p>There are many factors which could contribute to the Arctic warming: feedback processes like the lapse rate and ice-albedo feedback, the increasing downward longwave radiation caused by clouds and water vapour, and the reduction of sea ice in summer that leads to absorption of solar radiation and increase in local evaporation and more clouds. But also the atmospheric moisture transport from the lower latitudes can contribute to the surface warming in high-latitudes. This poleward moisture transport is mostly accomplished by extra-tropical cyclones, with especially strong contribution by the Atmospheric Rivers (ARs). ARs are long, narrow bands of enhanced water vapour transport which are responsible for over 90% of the poleward water vapour transport in and across mid-latitudes. Furthermore, they are responsible for producing significant levels of rain and snow. In addition, the greenhouse effect of water vapour and the formation of clouds increase the downward longwave radiation which can cause a thinning and melting of Arctic sea ice and snow.</p><p>In this study, we investigate the contribution of ARs to Arctic precipitation. Firstly, we look into different case studies for which observational data from the campaigns within the Collaborative Research Center “Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)<sup>3</sup>” exist. The data include enhanced observations at/around Svalbard performed during the ACLOUD and the AFLUX campaigns.</p><p>Previous studies have shown that ARs reaching into the Arctic have different origins, including the Atlantic and the Pacific pathways and also Siberia. Here we examine which pathway is more common and which one transports more moisture into the Arctic for these case studies by using existing AR catalogues from global and polar-specific algorithms. Furthermore, the variability of precipitation influences the surface mass and energy balance of polar sea ice and ice sheets. Therefore, we will analyse the influence of ARs on precipitation in terms of frequency, intensity, and type of precipitation (rain or snow) for the different case studies. For this purpose, we will use reanalyses and observational data for the water vapour transport, total precipitation, rain and snow profiles.The occurrence of ARs and its influence on precipitation will be extended from case studies to the long-term statistics (for at least 10 years).</p>

scholarly journals A critique on ‘A Boltzmann transformation method for investigation of water vapour transport in building materials’

2020 ◽  
pp. 174425912098004
Author(s):  
Hans Janssen
Keyword(s):  
Transport Properties ◽  
Water Vapour ◽  
Reference Values ◽  
Building Materials ◽  
Transformation Method ◽  
Dynamic Measurement ◽  
Vapour Transport ◽  
Vapour Permeability ◽  
Water Vapour Transport

In 2011, this journal published the paper ‘A Boltzmann transformation method for investigation of water vapour transport in building materials’, proposing a dynamic measurement of building materials’ vapour permeability via the Boltzmann-Matano method. This critique points out that this publication is flawed, since it proposes an invalid approach and presents erroneous results. The analysis first shows that the presented vapour permeability values cannot be reproduced and instead far lower vapour transport properties are obtained. These corrected outcomes are however also much below the dry-cup reference values, and it is established that these deviations stem from the invalidity of the proposed approach, due to disregarding the material’s hygroscopicity. Given its erroneous results and invalid approach, it is finally recommended to have the paper officially retracted by the journal.

scholarly journals Computational implementation of interfacial kinetic transport theory for water vapour transport in porous media

2014 ◽  
Vol 470 (2161) ◽  
pp. 20130278 ◽  
Author(s):  
Bashar Albaalbaki ◽  
Reghan J. Hill
Keyword(s):  
Porous Media ◽  
Aspect Ratio ◽  
Water Vapour ◽  
Transport Theory ◽  
Effective Diffusivity ◽  
Water Vapour Permeability ◽  
Vapour Transport ◽  
Computational Framework ◽  
Vapour Permeability ◽  
Water Vapour Transport

A computational framework is developed for applying interfacial kinetic transport theory to predict water vapour permeability of porous media. Modified conservation equations furnish spatially periodic disturbances from which the average flux and, thus, the effective diffusivity is obtained. The equations are solved exactly for a model porous medium comprising parallel layers of gas and solid with arbitrary solid volume fraction. From the microscale effective diffusivity, a two-point boundary-value problem is solved at the macroscale to furnish the water vapour transport rate in membranes subjected to a finite RH differential. Then, the microscale model is implemented using a computational framework (extended finite-element method) to examine the role of particle size, aspect ratio and positioning for periodic arrays of aligned super-ellipses (model particles that pack with high density). We show that the transverse water vapour permeability can be reduced by an order of magnitude only when fibres with a high-aspect ratio cross section are packed in a periodic staggered configuration. Maximum permeability is achieved at intermediate micro-structural length scales, where gas-phase diffusion is enhanced by surface diffusion, but not limited by interfacial-exchange kinetics. The two-dimensional computations demonstrated here are intended to motivate further efforts to develop efficient computational solutions for realistic three-dimensional microstructures.

scholarly journals Barrier Properties of Footwear Packages against Water Vapour Transport and Thermal Resistance

2021 ◽  
Vol 29 (1(145)) ◽  
pp. 70-74
Author(s):  
Wioleta Serweta ◽  
Małgorzata Matusiak ◽  
Justyna Wójcik
Keyword(s):  
Thermal Resistance ◽  
Water Vapour ◽  
Polyurethane Foam ◽  
Three Dimensional ◽  
Barrier Properties ◽  
Dimensional Structure ◽  
Vapour Transport ◽  
Knitted Fabrics ◽  
Vapour Permeability ◽  
Water Vapour Transport

In this paper the authors focused on the analysis of relations between the material (such as knitted fabrics with a two and three dimensional structure) configurations and hygienic parameters of packages. In order to measure hygienic properties, the water vapour permeability and absorption were both used with the thermal resistance capacity. The connector role in the packages measured was played by air (in the case of two – layered package), polyurethane foam and three – dimensional knitted fabric with similar characteristics to polyurethane foam in respect of the mass per square metre and thickness. On the basis of the results obtained, a statistical model of the barrier was created and the changes in water vapour transport process described.

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