scholarly journals Macro-Scale Numerical Simulation of Moisture Transmission in Zeoli-Based Moisture Conditioning Material

2021 ◽  
Vol 31 (1) ◽  
pp. 21-26
Author(s):  
Bo Zhou ◽  
Congyang Zou ◽  
Erlin Meng
Keyword(s):  
Porous Media ◽  
Water Vapor ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Pore Morphology ◽  
Pore Connectivity ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion ◽  
Growth Method ◽  
Random Growth

By random growth method, this paper constructs isotropic porous media, anisotropic-1 porous media, and anisotropic-2 porous media, which have the same porosity but different micropore morphologies, and explores how the pore morphology affects the water vapor diffusion in the pores of porous media. The results show that: the random growth method can effectively reconstruct various porous moisture conditioning materials, and control their porosity and pore morphology; the equilibrium water vapor concentration and stabilization time of water vapor diffusion can effectively demonstrate the pore connectivity of porous media and the dynamic migration features of materials in the pores; the greater the change in the equilibrium water vapor concentration, the faster the stabilization of water vapor diffusion, and the better the pore connectivity of porous media.

PORE STRUCTURE RECONSTRUCTION AND MOISTURE MIGRATION IN POROUS MEDIA

Fractals ◽  
2014 ◽  
Vol 22 (03) ◽  
pp. 1440007 ◽  
Author(s):  
JIAYI ZHENG ◽  
XING SHI ◽  
JUAN SHI ◽  
ZHENQIAN CHEN
Keyword(s):  
Porous Media ◽  
Water Vapor ◽  
Diffusion Process ◽  
Pore Structure ◽  
Pore Size ◽  
Spectral Dimension ◽  
Anisotropic Porous Media ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion ◽  
The Impact

Three kinds of porous media (isotropic, perpendicular anisotropic and parallel anisotropic porous media) with the same porosity, different pore size distributions and fractal spectral dimensions were reconstructed by random growth method. It was aimed to theoretically study the impact of microscopic pore structure on water vapor diffusion process in porous media. The results show that pore size distribution can only denote the static characteristics of porous media but cannot effectively reflect the dynamic transport characteristics of porous media. Fractal spectral dimension can effectively analyze and reflect pores connectivity and moisture dynamic transport properties of porous media from the microscopic perspective. The pores connectivity and water vapor diffusion performance in pores of porous media get better with the increase of fractal spectral dimension of porous media. Fractal spectral dimension of parallel anisotropic porous media is more than that of perpendicular anisotropic porous media. Fractal spectral dimension of isotropic porous media is between parallel anisotropic porous media and perpendicular anisotropic porous media. Other macroscopic parameters such as equilibrium diffusion coefficient of water vapor, water vapor concentration variation at right boundary in equilibrium, the time when water vapor diffusion process reaches a stable state also can characterize the pores connectivity and water vapor diffusion properties of porous media.

scholarly journals Numerical Simulation of the Water Vapor Separation of a Moisture-Selective Hollow-Fiber Membrane for the Application in Wood Drying Processes

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 593
Author(s):  
Nasim Alikhani ◽  
Douglas W. Bousfield ◽  
Jinwu Wang ◽  
Ling Li ◽  
Mehdi Tajvidi
Keyword(s):  
Water Vapor ◽  
Constant Temperature ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Vacuum Pressure ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Fiber Membrane ◽  
Wood Drying ◽  
Air Velocity

In this study, a simplified two-dimensional axisymmetric finite element analysis (FEA) model was developed, using COMSOL Multiphysics® software, to simulate the water vapor separation in a moisture-selective hollow-fiber membrane for the application of air dehumidification in wood drying processes. The membrane material was dense polydimethylsiloxane (PDMS). A single hollow fiber membrane was modelled. The mass and momentum transfer equations were simultaneously solved to compute the water vapor concentration profile in the single hollow fiber membrane. A water vapor removal experiment was conducted by using a lab-scale PDMS hollow fiber membrane module operated at constant temperature of 35 °C. Three operation parameters of air flow rate, vacuum pressure, and initial relative humidity (RH) were set at different levels. The final RH of dehydrated air was collected and converted to water vapor concentration to validate simulated results. The simulated results were fairly consistent with the experimental data. Both experimental and simulated results revealed that the water vapor removal efficiency of the membrane system was affected by air velocity and vacuum pressure. A high water vapor removal performance was achieved at a slow air velocity and high vacuum pressure. Subsequently, the correlation of Sherwood (Sh)–Reynolds (Re)–Schmidt (Sc) numbers of the PDMS membrane was established using the validated model, which is applicable at a constant temperature of 35 °C and vacuum pressure of 77.9 kPa. This study delivers an insight into the mass transport in the moisture-selective dense PDMS hollow fiber membrane-based air dehumidification process, with the aims of providing a useful reference to the scale-up design, process optimization and module development using hollow fiber membrane materials.

Measurement and Modeling of Water-Vapor Diffusion in Elastomers with Impact in Humidity and Vacuum Measurements

2013 ◽  
Vol 34 (3) ◽  
pp. 412-423 ◽  
Author(s):  
Janez Šetina ◽  
Makfir Sefa ◽  
Bojan Erjavec ◽  
Domen Hudoklin
Keyword(s):  
Water Vapor ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion

Degradation of Solid Oxide Fuel Cell Cathodes Accelerated at a High Water Vapor Concentration

2010 ◽  
Vol 7 (2) ◽  
Author(s):  
S. H. Kim ◽  
K. B. Shim ◽  
C. S. Kim ◽  
J. T. Chou ◽  
T. Oshima ◽  
...  
Keyword(s):  
Water Vapor ◽  
Voltage Drop ◽  
Cell Voltage ◽  
High Water ◽  
Solid Oxide ◽  
Constant Current ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Oxide Fuel ◽  
Constant Current Density

The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800°C and 1000°C. Cell voltage change was negligible at 1000°C, while considerable voltage drop was observed at 800°C accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La2O3 formed on the (La0.8Sr0.2)0.98MnO3 surface, which is assumed to be the reason for a large voltage drop.

scholarly journals A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

2018 ◽  
Vol 36 (13) ◽  
pp. 2667-2674 ◽  
Author(s):  
Arun Kumar Mallik ◽  
Gerald Farrell ◽  
Dejun Liu ◽  
Vishnu Kavungal ◽  
Qiang Wu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Low Humidity

Lime Plasters Containing Waste Ceramic Powder as Partial Replacement of Siliceous Aggregates

2014 ◽  
Vol 1035 ◽  
pp. 77-82 ◽  
Author(s):  
Eva Vejmelková ◽  
Monika Čáchová ◽  
Dana Koňáková ◽  
Pavel Reiterman ◽  
Robert Černý
Keyword(s):  
Water Vapor ◽  
Bending Strength ◽  
Ceramic Powder ◽  
Point Of View ◽  
Partial Replacement ◽  
Diffusion Resistance ◽  
Vapor Diffusion ◽  
Water Vapor Diffusion ◽  
Hollow Brick ◽  
Lime Plaster

Waste materials are utilized with an increasing frequency in the building industry, during the last decades. The motivation is both environmental and economical. In this paper, waste ceramic powder produced at the grinding of hollow brick blocks used in precise-walling technologies, is applied as a partial replacement of siliceous aggregates of lime plasters. The designed plaster mixes are analyzed from the point of view of their basic physical, mechanical, hygric and thermal properties. The bulk density, matrix density, open porosity, compressive strength, bending strength, water vapor diffusion permeability, water vapor diffusion coefficient, water vapor diffusion resistance factor, thermal conductivity and specific heat capacity are the investigated parameters. A reference lime plaster is analyzed as well, for the sake of comparison. Experimental results show a remarkable enhancement of mechanical properties of the plasters with the increasing dosage of ceramic powder. Moreover, the thermal insulation properties are improved and the water vapor diffusion capability of the plasters with ceramic powder increases.

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