| Civil Engineering, Transportation Engineering |
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| Transient determination of water vapor diffusion coefficient of porous building materials |
| YI Si yang1,JIN Hong qing1,FAN Li wu1,XU Xu2,YU Zi tao1,GE Jian3 |
| 1. Institute of Thermal Science and Power Systems,Zhejiang University,Hangzhou 310027,China；2. College of Metrological and Measurement Engineering,China Jiliang University,Hangzhou 310018,China；3. Institute of Architectural Technology,Zhejiang University,Hangzhou 310058,China |
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Abstract A transient method was proposed based on solving an inverse problem of transient one dimensional mass diffusion in order to shorten the measurement time for determination of the water vapor diffusion coefficient of porous building materials. A typical porous building material was taken as an example by choosing the type B04 autoclaved aerated concrete. The proposed transient method was implemented by dynamically monitoring the relative humidity distribution inside the sample with a set of capacitor based hygrometers. The water vapor diffusion coefficient was finally acquired via the solution of the inverse problem of transient one dimensional mass diffusion. Results showed that the transient results accorded with those measured by the steady state method with a maximum relative deviation being less than 30%. The proposed transient method only took several days to accomplish compared to the steady state method that lasted for more than 2 months. The significantly improved measurement efficiency was due to the fact that the variation of water vapor diffusion coefficient as a function of relative humidity can be determined by a single experiment．
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Published: 31 March 2016
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多孔建筑材料水蒸气扩散系数的瞬态测试方法
为了缩短多孔建筑材料水蒸气扩散系数的测试时间,提出基于求解瞬态一维质扩散反问题的瞬态测试方法.以典型的多孔建筑材料B04型加气混凝土为例,采用电容式相对湿度传感器对试样内部的相对湿度分布进行动态监测,以实现该瞬态测试方法,由瞬态一维质扩散反问题的解得到加气混凝土试样的水蒸气扩散系数.结果表明,瞬态测量值与通过稳态法测试得到的相同相对湿度下的值吻合度较高,最大偏差在30%以内.与耗时长达2个月以上的稳态法相比,该瞬态测试方法耗时仅需数天,可以仅由一次测试获得水蒸气扩散系数随相对湿度的变化规律曲线,极大地提高了测试效率.
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