Research On Coupled Heat And Moisture Transfer Characteristics Of Aerated Concrete Walls In Hot And Humid Climate

In hot and humid climate, the phenomenon that heat transfer and moisturemovement are highly coupled within the building materials is obvious. Heat andmoisture transfer through building have an important effect on the thermalperformance of building materials, the service life of building and indoor air quality.In the design of residential building envelope, a series of problems may happen whenwe solve a problem partially. For example, in some areas, in order to reduce energyconsumption, a lot of thermal insulation material is used in residential buildings,which make the building more closed. At the same, moisture indoor is hard to diffuseoutside. Too much moisture accumulation may lead to the decline of thermalperformance of the building materials, wall damage, and indoor air quality problemswhich caused by mildew.With increasing awareness of building energy saving, the use of insulation wall inhot-humid climate has received more and more attention. So we choose aeratedconcrete on behalf of the thermal insulation building materials, and EPS on behalf ofthe outside thermal insulation building materials. And then, we designed experimentsto study heat and moisture through aerated concrete wall and EPS external insulationaerated concrete wall in Changsha. The experimental results show that:(1) In aerated concrete wall, the temperature and humidity of the interfacebetween cement mortar and aerated concrete was strongly influenced by the outdoortemperature and humidity. And the temperature and humidity of the interface betweenplaster of cement and aerated concrete was strongly influenced by the indoortemperature and humidity.(2) In aerated concrete wall heat and moisture transfer were highly coupled.(3) Solar radiation has affected the temperature of the interface between cementmortar and aerated concrete more in sunny day than in rainy day. The outdoortemperature had a greater influence on the temperature of the interface betweenplaster of cement and aerated concrete in sunny day than in rainy day.(4) In rainy day, because of rainwater and more air moisture outside, the interfacebetween cement mortar and aerated concrete was soon moisture saturated. After therain, the outside humidity began to decrease, the interface has kept moisture saturation. However, due to its well-known waterproofing quality, relative humidity of theinterface between EPS and aerated concrete has increased, but was not saturat ed.(5) EPS external insulation aerated concrete wall has done well in heat insulationon a typical clear day in summer, which can largely reduce the indoor load. But in theother seasons, it didn’t work well. On the other side, relative humidity of interfacebetween EPS and aerated concrete was above80%in most time. That might lead tomold easy growing.Building materials used in experiments, such as aerated concrete, cement mortar,plaster of cement and EPS, are all porous media. This paper has introduced ahygrothermal model based on the theory of heat and mass transfer in porous media.The model was based on driving potentials of temperature and air moisture contentand has been elaborated the governing equations for moisture and energy balance. Thegoverning equations were solved by finite volume method. Comparing the simulationvalue and the experiment value, we found that the simulation value had goodagreement with the experiment value. The maximum of temperature was6.67K, themaximum of air moisture was5.36g/kg.