非均匀吸放湿过程对建材导热系数的影响

Influence of non-uniform moisture absorption and desorption on thermal conductivity of building materials

在针对含湿建材导热系数的研究中,预测模型一般假设材料含湿均匀,试验测量多采用均匀增湿方案,但实际使用过程中,受室内外湿度及气象条件影响,造成吸放湿过程中湿组分非均匀分布,相同含湿量下吸放湿过程中的材料导热系数存在差异。通过对孔隙特征不同的加气混凝土(AAC)、发泡水泥(FC)、红砖(RB)材料进行增减湿试验,控制试件在试验环境中的放置时间获得质量含湿量不均匀的试件,选择瞬态导热系数测量方案,通过分析含湿多孔建材增/减湿全过程导热系数变化趋势,研究非均匀湿分布材料导热系数变化特性。结果表明:AAC、FC、RB加湿过程导热系数相较干燥状态下分别增长了279%、266%、106%。增减湿过程中,含湿量相同的AAC导热系数差值范围约为-20.2%~63.4%,FC差值范围约为14.5%~53.3%,RB差值范围约为-18.0%~37.4%。

At present,for the study of the thermal conductivity of building materials containing moisture,the prediction model generally assumes that the materials containing moisture are uniform,and the experimental measurement usually adopts the uniform humidification scheme.However,the indoor and outdoor humidity and meteorological conditions influence building materials in the process of actural use,causing the non-uniform distribution of moisture components in the process of moisture absorption and desorption,and the thermal conductivity of the materials is different under the same moisture content.In this paper,the moisture content of autoclaved aerated concrete(AAC),foam cement(FC)and red brick(RB)materials with different pore characteristics were tested by analyzing the changing trend of thermal conductivity in the whole process of moisture-increasing and moisture-reducing, the changing characteristics of thermal conductivity in non-uniformmoisture-distributing materials were studied. The results show that the thermal conductivity of AAC, FC andRB in the humidification process increases by 279%, 266% and 106%, respectively, compared with that in thedry state. The difference value of thermal conductivity of ACC with the same moisture content in humidificationprocess is about -20.2%~63.4%, the difference value of FC is about 14.5%~53.3%, and the differencevaule of RB is about -18.0%~37.4%.