Conference Editor
Jianshun Zhang; Edward Bogucz; Cliff Davidson; Elizabeth Krietmeyer
Keywords:
Air pressure, Water absorption, Numerical analysis, Gamma-ray attenuation
Location
Syracuse, NY
Event Website
http://ibpc2018.org/
Start Date
24-9-2018 1:30 PM
End Date
24-9-2018 3:00 PM
Description
The effect of air pressure on moisture transfer inside porous building materials cannot be ignored in cases in which air cannot escape through the surfaces of the materials; in such cases, the air is compressed by the movement of the moisture. Therefore, in a situation in which most surfaces of a specimen are sealed or treated with surface-protecting materials (a situation that is often encountered in typical water-absorption tests), the experimental results may differ from those without sealed or treated surfaces. In the present study, the influence of air pressure on moisture transfer was investigated quantitatively. First, the following water-absorption test was conducted. Water infiltrated into a brick through its top surface, whereas the side surfaces were sealed to prevent the transfer of moisture and air. The bottom surface was exposed to the ambient air. The water content was measured twodimensionally during the experiment using gamma-ray attenuation. Next, to investigate how air pressure affects water infiltration, another experiment was conducted after sealing the bottom surface. The air inside the brick was expected to be compressed by the infiltrating water when the bottom surface was sealed. A water-absorption test was then performed after a small hole was made in a side surface of the bottom-sealed brick to reduce the interior air pressure. Finally, we analyzed the experiments numerically using a three-dimensional calculation model for simultaneous air and moisture transfer, assessing the validity of the model by comparing the calculated and measured water contents. The experimental and numerical results show that water infiltration is slowed by higher air pressure inside the specimen when it is difficult for air to escape. It is also shown that the hole in the side surface helped limit the rise in air pressure to some extent.
Recommended Citation
Fukui, Iba, Hokoi, and Ogura 'Effect of Air Pressure on Moisture Transfer inside Porous Building Materials Three-dimensional Behavior of Moisture and Air In Healthy, Intelligent, and Resilient Buildings and Urban Environments, Syracuse, NY: International Building Physics Association, 2018.
DOI
https://doi.org/10.14305/ibpc.2018.be-4.01
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Effect of Air Pressure on Moisture Transfer inside Porous Building Materials Three-dimensional Behavior of Moisture and Air
Syracuse, NY
The effect of air pressure on moisture transfer inside porous building materials cannot be ignored in cases in which air cannot escape through the surfaces of the materials; in such cases, the air is compressed by the movement of the moisture. Therefore, in a situation in which most surfaces of a specimen are sealed or treated with surface-protecting materials (a situation that is often encountered in typical water-absorption tests), the experimental results may differ from those without sealed or treated surfaces. In the present study, the influence of air pressure on moisture transfer was investigated quantitatively. First, the following water-absorption test was conducted. Water infiltrated into a brick through its top surface, whereas the side surfaces were sealed to prevent the transfer of moisture and air. The bottom surface was exposed to the ambient air. The water content was measured twodimensionally during the experiment using gamma-ray attenuation. Next, to investigate how air pressure affects water infiltration, another experiment was conducted after sealing the bottom surface. The air inside the brick was expected to be compressed by the infiltrating water when the bottom surface was sealed. A water-absorption test was then performed after a small hole was made in a side surface of the bottom-sealed brick to reduce the interior air pressure. Finally, we analyzed the experiments numerically using a three-dimensional calculation model for simultaneous air and moisture transfer, assessing the validity of the model by comparing the calculated and measured water contents. The experimental and numerical results show that water infiltration is slowed by higher air pressure inside the specimen when it is difficult for air to escape. It is also shown that the hole in the side surface helped limit the rise in air pressure to some extent.
https://surface.syr.edu/ibpc/2018/BE4/1
Comments
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