测量多孔材料含水/含冰量的热线法

Application of Hot-wire Technique to Measure Liquid Water and Ice Content within Porous Materials

保温材料的多孔特性使其在高湿环境下极易吸收大量的水分。保温材料中的水分将导致隔热隔音性能下降,并诱使发霉、腐蚀等现象。迄今,仍缺少一种针对多孔材料中水分含量的简单、廉价、快速、准确的无损伤在线检测方法。本文提出了一种基于瞬态热线法的水分检测方法,通过测量多孔材料吸水前后容积热容量的变化来反映材料中的含水量,容积热容量为导热系数与热扩散率的比值。将该方法应用于测量常温海绵中的液态含水量以及低温下的含冰量,实验结果表明热线法测得的含水量与高精度电子天平称出的实际含水量高度吻合,水分含量偏差在4%以内。

The porous insulation materials can easily acquire moisture once they are exposed to high humidity conditions. The acquired moisture may cause degradation of insulation performance, mould or bacteria growth,corrosion, etc. Currently, there is lack of an accurate, simple and inexpensive method for in-situ, nondestructive and rapid measurement of moisture content in porous materials. This investigation proposes to measure the moisture content by means of volumetric heat capacity using the transient hot-wire technique. The moisture content is calculated from the change of the volumetric heat capacity before and after the moisture acquirement, which is the ratio of the thermal conductivity with the thermal diffusivity. The proposed method was applied to determine both liquid water and ice contents in sponge blocks. The results show that the discrepancy of the measured moisture contents is within ±4%between the proposed method and the benchmark gravimetric method by a precision balance.