OBSERVATIONS ON THE PERMEABILITY OF HYGROSCOPIC MATERIALS TO WATER VAPOUR: I. OBSERVATIONS AT RELATIVE HUMIDITIES LESS THAN 75%

1940 ◽  
Vol 18a (6) ◽  
pp. 105-121 ◽  
Author(s):  
J. D. Babbitt
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Vapour Pressure ◽  
Fick’S Law ◽  
Moisture Movement ◽  
Fick's Law ◽  
Vapour Pressure Difference ◽  
Moisture Content Gradient ◽  
Vapour Pressure Gradient

It is pointed out that experimental work has shown that for the transpiration of moisture through hygroscopic materials two distinct regions of relative humidity can be distinguished: (i) A region below some value between 70 and 80% where the moisture movement is proportional to the vapour pressure difference, and (ii) a region of high relative humidity where the moisture movement is not directly proportional to the vapour pressure. A theory is advanced that these two regions correspond to the two conditions in which water may be present in a hygroscopic material: (i) the water may be molecularly adsorbed, that is to say, the water is bound by the affinity of the molecules of water for those of the solid on which it is adsorbed; (ii) the water may be held in small fissures in the sub-microscopic structure of the sorbing material by capillary forces. The mechanism by which the moisture will move through the material would be different in the two cases and would result in the distinction between regions of high and of low relative humidity.A short discussion is given of Fick's law showing the form in which it might be expected to apply in the two cases. Measurements are given for fibreboards showing that below 75% relative humidity the resistance of the board to moisture transpiration is proportional to the thickness. The moisture content gradients through fibreboard samples have been determined. The diffusance through a board in which the moisture content gradient is opposed to the vapour pressure gradient shows that the latter is the important factor, and the determination of the moisture content gradient indicates that at these low humidities Fick's law is applicable.

Determination of readiness for laying based on material moisture, corresponding relative humidity, and water release

2020 ◽  
Vol 62 (10) ◽  
pp. 1033-1040
Author(s):  
Christoph Strangfeld ◽  
Sabine Kruschwitz
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Embedded Sensors ◽  
Residual Water ◽  
Floor Covering ◽  
Water Release ◽  
Content Determination ◽  
Two Samples ◽  
Moisture Content Determination

Abstract The moisture content of the subfloor has to be determined before installation to avoid damage to the floor covering. Only if readiness for layering is reached, can an installation without damage be expected in all cases. In general, three approaches exist to measure residual water content: determination of moisture content, determination of water release, or determination of the corresponding relative humidity. All three approaches are tested under laboratory conditions at eight screed types including two samples thicknesses in each case. Moisture content and water release are measured by sample weighing, the corresponding relative humidity is measured by embedded sensors. All three approaches are compared and correlated. The evaluations show only a weak correlation and, in several cases, contradicting results. Samples are considered ready for layering and not ready for layering at the same time, depending on the chosen approach. Due to these contradicting results, a general threshold for a risk of damage cannot be derived based on these measurements. Furthermore, the experiment demonstrates that the measurement of corresponding relative humidity is independent of the screed type or screed composition considered. This makes humidity measurement a potentially very promising approach for the installation of material moisture monitoring systems.

Moisture Absorption and Diffusion Characterization of Molding Compound

2005 ◽  
Vol 127 (4) ◽  
pp. 460-465 ◽  
Author(s):  
Xu Chen ◽  
Shufeng Zhao ◽  
Linda Zhai
Keyword(s):  
Relative Humidity ◽  
Moisture Absorption ◽  
Saturated Vapor ◽  
Ambient Air ◽  
Second Phase ◽  
Fick’S Law ◽  
Moisture Concentration ◽  
Molding Compound ◽  
Fick's Law ◽  
Temperature And Humidity

The moisture absorption experiments of two kinds of molding compound are conducted. The diffusion at low temperature and humidity observes the Fick’s Law, but it does not strictly obey at higher temperature and humidity. The phenomena can be attributed to the occurrence of the second phase, and the Fick’s Law can be modified by diffusion coefficient varying with the moisture concentration. The predicted value by the modified Fick’s Law agrees with the test data. At certain temperature, the saturated moisture content of molding compound is proportional to the relative humidity, and the proportional factor is the product of solubility and saturated vapor pressure. The solubility is a physical characteristic, which has no relations with the relative humidity of ambient air.

Measurement and Characterization of the Moisture-Induced Properties of ACF Package

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Ji-Young Yoon ◽  
Ilho Kim ◽  
Soon-Bok Lee
Keyword(s):  
Diffusion Coefficient ◽  
Relative Humidity ◽  
Moisture Content ◽  
Chemical Interaction ◽  
Transient State ◽  
Length Change ◽  
Experimental Results ◽  
Moisture Movement ◽  
Humid Environment ◽  
Swelling Coefficient

This study is to observe the exact behavior of anisotropic conductive adhesion (ACF) package under humid environments by obtaining the moisture-induced properties such as diffusion coefficient (the rate of moisture movement into the materials), saturated moisture content (the maximum absorbed quantity), and swelling coefficient (length change due to the chemical interaction). So the experiments were performed to get the moisture-induced properties of ACF and FR4 using newly developed method at various temperature and relative humidity conditions. Experimental results showed that the diffusion coefficient of ACF and FR4 follows Arrhenius’ equation very well, and the saturated moisture content of them follows Henry’s law, which means linear relationship between saturated moisture content and relative humidity, but the saturated moisture content of ACF is influenced by temperature as well as relative humidity. And the swelling coefficient of ACF and FR4 increases with temperature. Especially in the case of ACF, it shows the dramatic degradation due to Tg (glass transition temperature) at nearby 85°C. Finally, as using these experimental results, the behavior of the ACF package under humid environment is predicted through finite element simulation. When wetness defined by moisture content over saturated moisture content changes from 0 to 0.9, the center of the ACF package is subject to compression and the edge of the ACF package is subject to tension in the case of transient state. After all, because the edge of the ACF package is very weak due to bending moment, the failure is easy to occur under humid environment.

scholarly journals Quality Assessment of Air-dried Teakwood Boards Using Moisture Content Gradients

2016 ◽  
Vol 24 (0) ◽  
Author(s):  
Djeison Cesar Batista ◽  
José Tarcísio da Silva Oliveira ◽  
Rená Porto Pizetta ◽  
Vinicius Munaldi Lube
Keyword(s):  
Moisture Content ◽  
Average Moisture Content ◽  
Drying Process ◽  
Air Drying ◽  
Kiln Drying ◽  
Moisture Meter ◽  
Environment Control ◽  
Moisture Content Gradient

ABSTRACT The determination of moisture content gradients is one of the most important steps for assessing the quality of wood drying. The general aim of this work was to study the quality of air-dried teakwood boards according to the gradients of moisture content in thickness and length. Six representative boards (40 × 180 × 2,300 mm) were sampled from a stack air-dried under shelter, divided into 30 equal parts in length and measured with a resistance moisture meter, resulting in four treatments: two depths (1/4 and 1/2 thickness) and two surfaces (inner and outer) of measurement. As main results, we can conclude that the air-drying quality can be considered good, mainly for two reasons: i) the average moisture content gradients in thickness were comparable to those reported in literature for kiln-drying of less thick boards; ii) the range of average moisture content among boards (2.5 p.p.) was satisfactory for a drying process carried out without environment control. Length moisture content gradient was completely different from that reported in literature, in which no board tops had smaller moisture content than the parts comprehended in between the tops.

scholarly journals Determination of effective binary diffusivity in anode of solid oxide fuel cell based on Fick’s law

2020 ◽  
Vol 7 (5) ◽  
pp. 20-00239-20-00239
Author(s):  
Masaaki IZUMI ◽  
Takuya NISHITERA ◽  
Hisashi SAKAMOTO ◽  
Miki MATSUI
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Fick’S Law ◽  
Fick's Law

Water Exchange in the Mantle of a Terrestrial Snail During Periods of Reduced Evaporative Loss

1972 ◽  
Vol 57 (1) ◽  
pp. 103-111
Author(s):  
J. MACHIN
Keyword(s):  
Steady State ◽  
Relative Humidity ◽  
Surface Temperature ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Water Exchange ◽  
Impermeable Barrier ◽  
Humidity Change ◽  
Evaporative Loss ◽  
Vapour Pressure Difference

1. Based on surface temperature, steady-state rates of evaporation of the mantle of inactive Otala lactea are very low even down to 1.5% relative humidity. 2. Mantle permeability is 0.016 mg/cm2/h per mmHg vapour pressure difference. 3. Marked peaks in surface temperature following humidity change are interpreted as net gain or loss of water to the mantle. 4. Smaller flucations in surface temperature are interpreted as limited mucusgland activity. 5. The existence of a superficial hygroscopic layer overlying an impermeable barrier in the mantle is discussed.

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