Study On Static Moisture Absorption And Desorption Characteristic Of Three Indoor Surface Materials And Their Surface Mass Transfer Coefficient

Studied have shown that,indoor surface materials can absorb one-third of the humidity produced in the room.In order to accurately analyze the influence of indoor surface materials on the indoor wet environment,it is necessary to study the moisture absorption and desorption characteristics of the material surface.In the view of the above problems,this thesis focuses on the moisture absorption and desorption process on the surface of the material and uses a combination of theoretical analysis and experimental methods to conduct research.The experiment obtains the moisture absorption and desorption capacity of the material surface to analyze the moisture absorption and desorption characteristics of the material.The research conclusions can be used to solve the same type of heat and mass transfer equation,the convective mass transfer coefficient of the material surface can provide a reference for the calculation of the mass transfer equation,and the rate of moisture absorption and desorption of diatom ooze can be a data reference used for the research and development of humidity control materials.First of all,the heat and moisture transfer mechanism of the material surface and the heat and moisture coupling transfer model of the material are analyzed in this thesis.According to the research purpose,the partial pressure of water vapor is taken as the only driving potential,and a suitable surface moisture absorption and desorption process is adopted for the heat and moisture coupling transfer model.Next,the rate of moisture absorption and desorption is used to reflect the moisture absorption and desorption characteristics of the material surface.The static moisture absorption and desorption experiment is carried out for three common surface materials which are basswood,tile and tile covered with diatom ooze in the buildings.This experiment obtains the rate of moisture absorption and desorption of the three surface materials,and analyzes the moisture absorption and desorption characteristics of the surfaces of the three materials.Finally,using the sublimation process of the naphthalene specimen,the test method of the surface convective mass transfer coefficient is obtained through theoretical deduction.And the convective mass transfer coefficient of the material surface,and the steps of obtaining the mass transfer coefficient are simplified.Using the relevant data obtained in the naphthalene sublimation experiment,the surface convective mass transfer coefficients of the three materials are calculated through the simplified steps of the mass transfer coefficients.The test of static moisture absorption and desorption results of three indoor surface materials show that the rate of moisture absorption and desorption of basswood and tile covered with diatom ooze are relatively similar and have higher values.The rate of moisture absorption and desorption of the two materials are relatively high.Both are more than twice that of tile,indicating that the two materials have better moisture absorption and desorption properties than tile.In an air-conditioned environment,that is,when the indoor relative humidity is 50%,the moisture absorption rate of the diatom ooze is 1.02 times that of the basswood,and the rate of moisture desorption of the basswood is 1.12 times that of the diatom ooze.The performance of the basswood is better than the diatom ooze when the indoor relative humidity is maintained at 50%.When the air conditioning is off,outdoor air with high relative humidity(similar to the temperature of indoor air)enters the room and increases the relative humidity of indoor air environment.From the comparison of the rate of moisture absorption between the diatom ooze and the basswood,it can be seen that the basswood has a faster rate of moisture absorption and can stabilize the indoor wet environment faster.But in indoor air relative humidity is 80%,the rate of moisture desorption of basswood only 52%of the rate of moisture absorption,and the rate of moisture desorption of diatom ooze only 88%of the rate of moisture absorption,when indoor relative humidity decreased from high humidity to low humidity,diatom ooze can quickly absorb the moisture content of the release,diatom ooze than basswood under the environment of high relative humidity can better regulate indoor wet environment.The test method of surface convection mass transfer coefficient is obtained through theoretical deduction,and the results show that,the average surface mass transfer coefficient of basswood in the process of moisture absorption and desorption are 1.904 × 10-5m/s and 1.451×10-5 m/s,tile in the moisture absorption and desorption process average surface to spread coefficient are 1.352×10-5m/s and 1.351 × 10-5m/s,tile covered with diatom ooze in moisture absorption and desorption process of average surface to spread coefficient were 1.758×10-5m/s and 1.388×10-5m/s.