ON THE FLOW OF GASES AND WATER VAPOR THROUGH WOOD

1950 ◽  
Vol 28a (4) ◽  
pp. 389-410 ◽  
Author(s):  
P. M. Pfalzner
Keyword(s):  
Diffusion Coefficient ◽  
Water Vapor ◽  
Relative Humidity ◽  
Hydrodynamic Flow ◽  
Flow Conditions ◽  
Flow Processes ◽  
External Conditions ◽  
Kinetic Diffusion ◽  
Pass Through ◽  
Distinct Features

The quantities of water vapor passing through wood have been measured under the conditions of hydrodynamic flow and of kinetic diffusion. Air and oxygen pass through wood under hydrodynamic flow conditions in accordance with the Knudsen–Poiseuille law. Water vapor passes through wood under hydrodynamic flow conditions in much larger quantities than those predicted by the law. The rate of passage of water vapor under diffusion conditions follows the Fick diffusion law but with a diffusion coefficient that increases with relative humidity. The distinct features of the diffusion and hydrodynamic flow processes are pointed out. Porous, hygroscopic media permit the transfer of water vapor either by diffusion or by hydrodynamic flow, as determined by two distinct sets of conditions, while compact, hygroscopic media permit the transfer of water vapor by diffusion only, regardless of the external conditions.

scholarly journals Temperature-dependent diffusion coefficient of H<sub>2</sub>SO<sub>4</sub> in air: laboratory measurements using laminar flow technique

2016 ◽  
Author(s):  
David Brus ◽  
Lenka Skrabalova ◽  
Erik Herrmann ◽  
Tinja Olenius ◽  
Tereza Travnickova ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Sulfuric Acid ◽  
Relative Humidity ◽  
Laminar Flow ◽  
Diffusion Coefficients ◽  
Loss Rate ◽  
Rate Coefficients ◽  
Flow Conditions ◽  
Flow Tube ◽  
Wall Loss

Abstract. We report measurements of the diffusion coefficient of sulfuric acid in humidified air at a range of relative humidities (from ~4 to 70 %), temperatures (278, 288 and 298 K) and initial H2SO4 concentration (from 1 × 10e6 to 1 × 10e8 molec. cm−3). The diffusion coefficients were estimated from the sulfuric acid wall loss rate coefficients under laminar flow conditions. The flow conditions were verified with additional fluid dynamics model CFD-FLUENT simulations which also reproduced the loss rate coefficients very well at all three temperatures with the maximum difference of 7 % between the measured and simulated values. The concentration of H2SO4 was measured continuously with chemical ionization mass spectrometer (CIMS) at seven different positions along the flow tube. The wall losses of H2SO4 were determined from the slopes of fits to measured H2SO4 concentrations as a function of the position along the flow tube. The observed wall loss rate coefficients, and hence the diffusion coefficients, were independent of different initial H2SO4 concentrations and different total flow rates. However, the determined diffusion coefficients decreased with increasing relative humidity, as also seen in previous experiments, and had a rather strong power dependence of the diffusion coefficient with respect to temperature, around ∝T5.4, which is in disagreement with the expected temperature dependency of ~T1.75 observed for other gases and not tested before for sulfuric acid. The effect of relative humidity on the diffusion coefficient is likely due to stronger hydration of H2SO4 molecules and likely also due to the presence of trace impurities such as amines, possibly brought to the system by humidification. Clustering kinetics simulations using quantum chemical data suggest that also the strong temperature dependence of the observed diffusion coefficient might be explained by increased diffusion volume of H2SO4 molecules due to stronger clustering with base-impurities like amines.

Absorption of Water Vapor Using Superabsorbent Polymer Composite Material

2020 ◽  
Vol 858 ◽  
pp. 129-139
Author(s):  
Ariel Verzosa Melendres ◽  
Rolan Pepito Vera Cruz
Keyword(s):  
Composite Material ◽  
Water Vapor ◽  
Relative Humidity ◽  
Pure Water ◽  
Polymer Composite Material ◽  
Air Transport ◽  
Water Vapor Absorption ◽  
Vapor Absorption ◽  
Digital Microscope ◽  
Pass Through

The ability of superabsorbent polymers (SAP) to absorb water vapor was studied. A multilayer composite material was prepared where SAP particles were spread in the fluffy fibrous layer located in the middle of the composite structure. Distribution of SAP within the composite material permits air to pass through its porous structure effectively hence allowing efficient contact of air with SAP. SAP was able to decrease the relative humidity of air of a 3-L cabinet from 96% relative humidity (RH) to 52% and 49 % (RH) in 18 hours using 2 g and 4 g of SAP respectively. Study on the water vapor absorption ability of SAP placed together with pure water in a closed cabinet was conducted with and without convective air transport effect. Convective air transport was done by activating the 12 V fan allowing air recirculation speed at rates corresponding to constant voltage settings of 6 V and 12 V. Higher SAP water vapor absorption rate was obtained at higher air recirculation speed. SAP particles swelled after water vapor absorption with slight decrease in the porosity of composite material as observed through the digital microscope.

Hydrodynamic flow conditions through permeable walls

1992 ◽  
Vol 2 (8) ◽  
pp. 1565-1569
Author(s):  
S. Vollmar ◽  
J. A. M. S. Duarte
Keyword(s):  
Hydrodynamic Flow ◽  
Flow Conditions ◽  
Permeable Walls

scholarly journals HGPT2: An ERA5-Based Global Model to Estimate Relative Humidity

2021 ◽  
Vol 13 (11) ◽  
pp. 2179
Author(s):  
Pedro Mateus ◽  
Virgílio B. Mendes ◽  
Sandra M. Plecha
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Real Time ◽  
Prediction Models ◽  
Weather Prediction ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Global Navigation Satellite Systems ◽  
International Gnss Service ◽  
Weighted Mean Temperature

The neutral atmospheric delay is one of the major error sources in Space Geodesy techniques such as Global Navigation Satellite Systems (GNSS), and its modeling for high accuracy applications can be challenging. Improving the modeling of the atmospheric delays (hydrostatic and non-hydrostatic) also leads to a more accurate and precise precipitable water vapor estimation (PWV), mostly in real-time applications, where models play an important role, since numerical weather prediction models cannot be used for real-time processing or forecasting. This study developed an improved version of the Hourly Global Pressure and Temperature (HGPT) model, the HGPT2. It is based on 20 years of ERA5 reanalysis data at full spatial (0.25° × 0.25°) and temporal resolution (1-h). Apart from surface air temperature, surface pressure, zenith hydrostatic delay, and weighted mean temperature, the updated model also provides information regarding the relative humidity, zenith non-hydrostatic delay, and precipitable water vapor. The HGPT2 is based on the time-segmentation concept and uses the annual, semi-annual, and quarterly periodicities to calculate the relative humidity anywhere on the Earth’s surface. Data from 282 moisture sensors located close to GNSS stations during 1 year (2020) were used to assess the model coefficients. The HGPT2 meteorological parameters were used to process 35 GNSS sites belonging to the International GNSS Service (IGS) using the GAMIT/GLOBK software package. Results show a decreased root-mean-square error (RMSE) and bias values relative to the most used zenith delay models, with a significant impact on the height component. The HGPT2 was developed to be applied in the most diverse areas that can significantly benefit from an ERA5 full-resolution model.

scholarly journals Deuterium excess in marine water vapor: Dependency on relative humidity and surface wind speed during evaporation

2014 ◽  
Vol 119 (2) ◽  
pp. 584-593 ◽  
Author(s):  
Marion Benetti ◽  
Gilles Reverdin ◽  
Catherine Pierre ◽  
Liliane Merlivat ◽  
Camille Risi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Speed ◽  
Relative Humidity ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Marine Water ◽  
Deuterium Excess

Influence of Temperature and Relative Humidity on Perm-Selectivity of PET Packaging Film

2011 ◽  
Vol 295-297 ◽  
pp. 1206-1210
Author(s):  
Yan Feng Guo ◽  
Xian Ping Ma ◽  
Yu Yan ◽  
Yun Gang Fu
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Experimental Studies ◽  
Thermodynamic Temperature ◽  
Packaging Film ◽  
Influence Of Temperature ◽  
Carbon Dioxide Gas ◽  
Pet Film ◽  
Pet Films ◽  
Temperature Water

The main feature of this article is the investigation on the influence of temperature, relative humidity, film thickness on permeability of PET packaging film, the analysis of perm-selectivity of the packaging films for oxygen gas and carbon dioxide gas, and the evaluation on experimental formulas of water vapor, O2 and CO2 gas permeating rates on the basis of gas molecular osmotic reaction kinetics and regression analysis. The comparison between experimental studies and calculation indicates that: (1) with increment of ambient temperature water vapor, O2 and CO2 permeating rate of PET films and PET/Al film also rise, and the logarithm of water vapor, O2 and CO2 gas permeating rates has linear relation with the reciprocal of thermodynamic temperature, and (2) the influence of relative humidity on water vapor permeating rate of PET film with thickness 12µm is the least, and that of PET film with thickness 20µm and PET/Al film with thickness 18µm is a little obvious. (3) The PET films hold remarkable perm-selectivity for O2 and CO2 gas, and CO2 gas permeating rate is about two times of O2 gas, yet O2 and CO2 gas permeating rates of PET/Al film are both very low and have small difference, so the PET/Al film has better barrier performance than the PET film.

Cell Adhesion Under Hydrodynamic Flow Conditions

1995 ◽  
Vol 15 (1) ◽  
Author(s):  
Priya K. Gopalan ◽  
David A. Jones ◽  
Larry V. McIntire ◽  
C. Wayne Smith
Keyword(s):  
Cell Adhesion ◽  
Hydrodynamic Flow ◽  
Flow Conditions
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