多孔介质湿物理性质预测方法综述

Review of Prediction Methods for the Hygric Properties of Porous Media

多孔建筑材料的湿物理性质是分析建筑围护结构热湿传递的重要基本参数。自20世纪80年代开始,欧美发达国家已针对常见建筑材料的湿物理性质开展多个大型测试项目,建立了涵盖上百种多孔建筑材料湿物理性质的基础数据库。我国学者从20世纪60年代开始研究多孔建筑材料的湿物理性质,至今已有一定积累,但在湿物理性质研究的广度和深度上尚需进一步探索;近年来,我国许多学者积极开展多孔建筑材料湿物理性质的研究工作,并取得明显进展。由于原材料及工艺等方面的差别,国际上的湿物理性质数据库在我国并非完全适用。因此,针对我国常见建筑材料,需要建立自主、完备、可靠的数据库。为获得材料的湿物理性质,最常用的是实验测试方法,但部分测试方法存在耗时长、操作复杂、仪器昂贵等问题。例如,等温吸放湿曲线可能需要数月甚至数年才能完成测试,压力平板实验操作流程复杂且对压力控制精度要求较高,而用于液态水扩散系数测试的X射线仪或核磁共振仪等设备价格较高,不利于常规实验室普及。多孔建筑材料与土壤、纤维、岩石、食品等都属于多孔介质,并且湿分的储存和传递性质都是其研究的关键参数。例如,保水曲线是研究旱地土壤的必要指标,湿扩散系数是评价织物热舒适度的重要参数,湿渗透系数影响石油的开采效率,等温吸放湿曲线决定食物的保鲜时长。为快速、准确获得土壤、纤维、岩石、食品等多孔介质的湿物理性质,学者们开展了大量运用已知物理性质预测未知湿物理性质的方法研究。本文总结了多孔介质湿物理性质的预测方法,归纳其优缺点,探讨将其运用于多孔建筑材料上的可能性,以期预测方法能与测试方法互为补充,为高效获得多孔建筑材料的湿物理性质提供帮助。

The hygric properties of porous building materials are indispensable in the analysis of heat and moisture transfer in building envelopes. Since the 1980s, European and American countries have carried out a number of large-scale test projects for the hygric properties of typical buil-ding materials. These projects established basic databases covering hundreds of building materials’ hygric properties. Chinese scholars began to study the hygric properties of porous building materials in the 1960s, but further exploration is still needed. In recent years, the research of buil-ding materials’ hygric properties has been actively carried out by Chinese scholars and noticeable progress has been made. Due to the differences in raw materials and manufacturing processes, the international databases are not fully applicable in China. Therefore, it is necessary to establish an independent, complete and reliable database for typical building materials in China. In order to obtain the hygric properties, the most commonly used method is through experiments. Some test methods, however, are time and energy consuming. For example, it may take months or even years to complete the measurement on sorption isotherms. The operation process of pressure plate test is complex and requires high accuracy in pressure control. Meanwhile, the X-ray or nuclear magnetic resonance instrument used to test the liquid diffusivity is expensive and not suitable for laboratory popularization. Similar to most building materials, soil, fiber, rock and food are all porous media, and their hygric properties are the key parameters to study the storage and transfer of moisture. For example, the water retention curve is a necessary index for studying dryland soil;diffusivity is an important parameter for evaluating the thermal comfort of fabrics;permeability affects the efficiency of oil extraction;and sorption isotherms determine the preservation time of food. In order to quickly and accurately obtain their hygric properties, scholars have carried out a lot of research on the method of using known physical properties to predict the unknown hygric properties of soil, fiber, rock and food. This paper reviews the prediction methods for the hygric properties of such porous media, summarizes their pros and cons, and discusses their application possibility on porous building materials. The target is to combine experiments with prediction methods, in order to effectively obtain the hygric properties of porous building materials.