含有初始饱和度的毛细吸水过程的解析模型研究

Analytical Model Study of Capillary Absorption Process with Initial Saturation

建筑围护结构中的液态水传递对建筑能耗及建筑耐久性有着重要影响。准确描述液态水在毛细作用下的自发渗吸过程可以用于评估液态水对建筑体的影响。以典型天然建筑多孔材料Bentheimer砂岩为研究对象,基于理论分析,推导了含有初始饱和度的多孔材料自发渗吸过程的解析模型,并预测了初始含水饱和度为3%~15%下的毛细吸水系数和内部饱和度分布,同时,我们通过标准毛细吸水实验对模拟结果进行验证。实验结果表明,随着初始饱和度的增加,材料的毛细吸水系数从(0.339±0.03) kg/(m^(2)·s^(0.5))降低到(0.253±0.02) kg/(m^(2)·s^(0.5)),与模拟结果吻合。同时,实验测得最终含水饱和度为0.510±0.007,与模型预测结果0.515±0.023相差在1%以内,证明模型具有一定的准确性,可以为建筑热工设计提供指导。

The liquid water transfer in building envelope plays an essential role in energy efficiency and durability. It is necessary to describe the spontaneous imbibition for evaluating the influence of liquid transfer in the porous media driven by capillary pressure. An analytical model is established to describe the process of spontaneous imbibition and study the capillary water absorption coefficient and saturation profile for nature building material Bentheimer sandstone with different initial saturation like 3%~15%. Then, we verified the model by standard capillary absorption test. According to the experimental result, the capillary water absorption coefficient decreases from(0.339±0.03) kg/(m^(2)·s^(0.5)) to(0.253±0.02) kg/(m^(2)·s^(0.5)) with the increase of the initial saturation, which matches the result of the model well. Meanwhile, the predicted final saturation of the model is 0.515±0.023 which has around 1% deviation compared with the result of the experiment 0.510±0.017. It means this model could be used to guide structure design.