Steam osmosis[1]Vapor permeation refers to the phenomenon that water vapor molecules permeate and diffuse from the side with high partial pressure to the side with low partial pressure when there is a water vapor partial pressure difference on both sides of the enclosure structure.The amount of steam penetration is directly proportional to the air permeability of the materials of the enclosure structure and the differential pressure of steam on both sides, and inversely proportional to the thickness of the structure.
Chinese name
Steam osmosis
Foreign name
vapor permeation
Conditions
There is water vapor partial pressure difference on both sides of the enclosure structure
Steam penetration
Inversely proportional to the thickness of the structure
In the natural environment, building structures are often affected by heat and humidity.There is a large amount of water in the external environment of the building. As time goes by, the water will soak into the interior of the building envelope through various ways.Both too high and too low humidity will affect the comfort of users, the service life of buildings, and reduce the service quality of buildings.At the same time, the durability andheat preservationThermal insulation is not conducive to building energy conservation.It also leads to the reduction of the strength of the building envelope, the peeling off of the veneer, deformation and other phenomena, so it is meaningful to study the wet condition of the building envelope.
Development prospect
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Steam osmosis is a new membrane separation process for vapor phase dehydration. It uses steam feed to realize mixture separation by taking advantage of the difference in solubility and diffusion performance of each component in the membrane under the promotion of the pressure difference of each component in the mixture.The application of steam osmosis technology in the separation of near boiling point, constant boiling point and isomers has its unique advantages. It can also be coupled with biological and chemical reactions to continuously remove reaction products, which significantly improves the reaction conversion rate. Its technical and economic advantages are obvious. It has broad application prospects in petrochemical industry, medicine, food, environmental protection and other industrial fields[2]。
Influencing factors of steam permeation
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The factors affecting the moisture condition of building envelope mainly include the moisture absorbed by the envelope from the air during use;The water in the land that penetrates into the enclosure structure, the original humidity of the materials used for the enclosure structure, and the water that enters into the enclosure structure materials during construction, etc.
summary
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Vapor permeation is a process of water vapor molecule transfer.If the water vapor content in the air on both sides of the room and the outside is different, there will be a pressure difference. The water vapor molecules with high pressure will gradually permeate through the enclosure structure to the other side. This phenomenon is usually called the steam infiltration of the enclosure structure. Not only is the water vapor migration caused by the temperature difference between the room and the outside, but also the water vapor migration caused by the partial pressure difference of water vapor,With the migration of saturated steam and liquid water, it is difficult to calculate by objective conditions.Therefore, the moisture condition of the envelope is analyzed according to the pure water vapor infiltration under the steady state condition[3]。
