Impact of Interstitial Mass Transport Resistance on Water Vapor Diffusion Through Fabric Layers

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Anshul Sharma ◽  
Sandra K. S. Boetcher ◽  
Walid A. Aissa ◽  
Matthew J. Traum
Keyword(s):  
Water Vapor ◽  
Mass Transport ◽  
Single Layer ◽  
Standard Test ◽  
Test Method ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Evaporative Resistance ◽  
Experimental Apparatus ◽  
Significant Magnitude

Textiles maintain wearer comfort by allowing evaporated sweat to permeate through, providing thermal management and keeping skin dry. For single layers, resistance to mass transport is relatively straightforward. However, when textiles are layered, water vapor transport becomes more complex because diffusing molecules must traverse interstitial spaces between layers. Interstitial mass transport resistances of significant magnitude can reduce rates of water vapor transport through layered textile stacks. The prevailing textile mass transport resistance interrogation method is ASTM F1868: “Standard Test Method for Thermal and Evaporative Resistance of Clothing Materials Using a Sweating Hot Plate.” Four improvements to ASTM F1868 are recommended: (1) gravimetric mass transport measurement, (2) evaluating transport using the Stefan flow model, (3) correct accounting for apparatus mass transport resistances, and (4) recognizing and measuring interstitial mass transport resistances. These improvements were implemented and evaluated by running tests using Southern Mills Defender™ 750 fabric, the calibration standard used for ASTM F1868, on a new gravimetric experimental apparatus. For a single layer of calibration fabric, the gravimetric approach is consistent with the prescribed result from ASTM F1868; however, for stacks of two or more calibration fabric layers, the gravimetric approach does not agree with the prescribed ASTM F1868 result due to interstitial mass transport resistance between fabric layers.

Impact of Interstitial Mass Transport Resistance on Water Vapor Diffusion Through Southern Mills Defender™ 750 Fabric Layers

2011 ◽  
Author(s):  
A. Sharma ◽  
S. K. S. Boetcher ◽  
W. A. Aissa ◽  
M. J. Traum
Keyword(s):  
Water Vapor ◽  
Mass Transport ◽  
Gravimetric Method ◽  
Single Layer ◽  
Test Method ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Working Fluid ◽  
Experimental Apparatus ◽  
Fabric Layer

Textiles maintain wearer comfort by allowing evaporated sweat to permeate through, providing thermal management and keeping skin dry. Each textile layer presents a resistance to mass transport consistent with its physical structure (i.e., thickness, porosity, and tortuosity). However, when textiles are layered, water vapor transport becomes more complex because diffusing molecules must traverse interstitial spaces between layers. Interstitial mass transport resistances of significant magnitude can reduce rates of water vapor transport through layered textile stacks. The prevailing textile mass transport resistance interrogation method is ASTM F1868: “Standard Test Method for Thermal and Evaporative Resistance of Clothing Materials Using a Sweating Hot Plate.” A self-calibrating element of this method is to measure one, two, three, and four fabric layers. Each newly added layer is prescribed to increase the stack mass transport resistance by the integer resistance presented by a single layer with no interstitial resistance consideration. Four improvements to ASTM F1868 are recommended: 1) gravimetric mass transport measurement, 2) a Stefan flow model, 3) correct accounting for apparatus mass transport resistances, and 4) recognizing and measuring interstitial mass transport resistances. These improvements were implemented and evaluated by running tests using Southern Mills Defender™ 750 fabric, the calibration standard used for ASTM F1868, on a new gravimetric experimental apparatus. The mass transport resistance of one fabric layer measured via the gravimetric method is related to the ASTM F1868 value through working fluid properties. Using the gravimetric approach, mass transport resistance for a single layer of calibration fabric was measured at 60.3 ± 14.4 s/m, which is consistent with the prescribed result from ASTM F1868 (after the conversion factor), 73.1 ± 7.3 s/m. The diffusion coefficient for water vapor in air in the fabric pores measured by gravimetric experiment, (2.02 ± 0.59) × 10−5 m2/s, agrees (within experimental uncertainty) with the theoretical value for the experimental conditions, 2.54 × 10−5 m2/s. However, for stacks of two or more calibration fabric layers, the gravimetric approach does not agree with the prescribed ASTM F1868 result due to interstitial mass transport resistance between fabric layers. The measured interstitial resistance value is 23.6 s/m, 39.1% of a single fabric layer, a value too significant to be ignored in engineering analysis.

scholarly journals Development of the Predictive Models for the Fabric Water Vapor Resistance

2011 ◽  
Vol 6 (2) ◽  
pp. 155892501100600 ◽  
Author(s):  
Sara Irandoukht ◽  
Akbar Irandoukht
Keyword(s):  
Water Vapor ◽  
Transport Properties ◽  
Linear Models ◽  
Nonlinear Models ◽  
Test Methods ◽  
Standard Test ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Absolute Deviation ◽  
Maximum Absolute Deviation

The water vapor transport properties of textile fabrics are of considerable importance in determining thermal comfort properties of clothing systems. There are different standard test methods available for measuring water vapor transport properties of fabrics. They are either time consuming or expensive methods. Objective of this work is to determine water vapor transmission resistance of the fabric using other properties of the fabric in such a manner that one can predict water vapor resistance. Both linear and nonlinear models were considered and different measures of model adequacy including residual sum of square, maximum absolute deviation and average absolute deviation were calculated. Using linear regression techniques, several statistically acceptable linear models were developed. The results revealed that several non-linear models can predict the water vapor resistance better than linear models.

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

scholarly journals Analysis of Intense Poleward Water Vapor Transports into High Latitudes of Western North America

2009 ◽  
Vol 24 (6) ◽  
pp. 1732-1747 ◽  
Author(s):  
Alain Roberge ◽  
John R. Gyakum ◽  
Eyad H. Atallah
Keyword(s):  
Water Vapor ◽  
North America ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Western Coast ◽  
Synoptic Scale ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Subtropical Oceans ◽  
Pineapple Express

Abstract Significant cool season precipitation along the western coast of North America is often associated with intense water vapor transport (IWVT) from the Pacific Ocean during favorable synoptic-scale flow regimes. These relatively narrow and intense regions of water vapor transport can originate in either the tropical or subtropical oceans, and sometimes have been referred to as Pineapple Express events in previous literature when originating near Hawaii. However, the focus of this paper will be on diagnosing the synoptic-scale signatures of all significant water vapor transport events associated with poleward moisture transport impacting the western coast of Canada, regardless of the exact points of origin of the associated atmospheric river. A trajectory analysis is used to partition the events as a means of creating coherent and meaningful synoptic-scale composites. The results indicate that these IWVT events can be clustered by the general area of origin of the majority of the saturated parcels impacting British Columbia and the Yukon Territories. IWVT events associated with more zonal trajectories are characterized by a strong and mature Aleutian low, whereas IWVT events associated with more meridional trajectories are often characterized by an anticyclone situated along the California or Oregon coastline, and a relatively mature poleward-traveling cyclone, commonly originating in the central North Pacific.

A Theoretical Model of Localized Heat and Water Vapor Transport in the Human Respiratory Tract

1986 ◽  
Vol 108 (1) ◽  
pp. 19-27 ◽  
Author(s):  
L. M. Hanna ◽  
P. W. Scherer
Keyword(s):  
Water Vapor ◽  
Theoretical Model ◽  
Respiratory Tract ◽  
Air Conditioning ◽  
High Stress ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Upper Respiratory Tract ◽  
Transfer Coefficients ◽  
Human Respiratory Tract

A steady-state, one-dimensional theoretical model of human respiratory heat and water vapor transport is developed. Local mass transfer coefficients measured in a cast replica of the upper respiratory tract are incorporated into the model along with heat transfer coefficients determined from the Chilton-Colburn analogy and from data in the literature. The model agrees well with reported experimental measurements and predicts that the two most important parameters of the human air-conditioning process are: 1) the blood temperature distribution along the airway walls, and 2) the total cross-sectional area and perimeter of the nasal cavity. The model also shows that the larynx and pharynx can actually gain water over a respiratory cycle and are the regions of the respiratory tract most subject to drying. With slight modification, the model can be used to investigate respiratory heat and water vapor transport in high stress environments, pollutant gas uptake in the respiratory tract, and the connection between respiratory air-conditioning and the function of the mucociliary escalator.

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