Study On Heat And Moisture Transfer Performance Of New Type Of Prefabricated Building Wall Materials

The development of assembly building is a major change in building construction mode,an important measure to promote the structural reform of supply side and the development of new-type urbanization.New-type assembly building wallboard is an important part of assembly building.However,due to the lack of heat-moisture coupling transfer performance parameters of new type fabricated building wallboard materials,the study of wallboard performance has encountered obstacles.In this paper,the thermal and moisture transfer properties of ceramsite foam concrete wall panels and the new wall materials such as lightweight aggregate concrete slab,glass fiber reinforced concrete slab(GRC board)and fiber cement board(FC board)have been studied by theoretical analysis and physical test.1)The thermal and moisture coupling model of the wall with the moisture content and temperature as the driving force is established,and the parameters of the material’s thermal and wet properties required for the model are determined.2)The equilibrium moisture content of five kinds of wall materials under 8 different relative humidities was studied by static method test.The BET formula and Caurie formula were determined to be more reasonable and accurate fitting formula.The equilibrium moisture content of the five materials increases monotonically with the relative humidity of the air,and increases rapidly in the range of 40%~100% relative humidity.3)The thermal conductivity of five kinds of wall materials under 8 different moisture contents was studied by transient method test,and the corresponding fitting formula was obtained.The thermal conductivity increases monotonously with the equilibrium moisture content of the material,and the relative increase in the relative humidity of 88.6%~100% becomes smaller and approaches a constant.4)The water vapor diffusion coefficient of five kinds of wall materials was studied by the moisture permeable cup method,and the corresponding fitting formula was obtained.The water vapor diffusion coefficient increases with the relative humidity as a power function.In the interval of 0~50% relative humidity,the increase is small,which can be regarded as a constant.In the interval of 50%~60%,the three concrete materials still increase less.The water vapor diffusion coefficient of the two cement sheets has increased rapidly;in the interval of 80% to 100%,it increases rapidly.5)The liquid water diffusion coefficient of five kinds of wall materials was studied by partial wetting method,and the corresponding fitting formula was obtained.The liquid water diffusion coefficient increases monotonically with the equilibrium moisture content.Combined with the isothermal absorption and desorption curve,it can be found that the variation is small in the range of 0~70% relative humidity.In the interval of 70%~88.6%,the growth rate of each material is different.However,in the 88.6%~100% range,they all increased rapidly.6)On the basis of the above,two types of self-developed new prefabricated building wall panels of type II ceramsite foam concrete exterior wallboard and lightweight aggregate concrete sandwich composite wallboard are applied to the cold(B)zone of the applicable area.The heat and humidity transfer performance was analyzed.The internal temperature distribution of the wallboard and the distribution of water vapor partial pressure were studied.The analysis was carried out from the inside of the wall panel and the condensation on the inner surface.These two independent research and development wall panels are suitable for cold.(B)District.