CONSTRUCT-LFC, Department of Civil Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal.
Department of Civil Engineering, Polytechnic Institute of Viseu, Campus Politécnico de Repeses, 3504-510 Viseu, Portugal.
Sensors (Basel). 2020 Mar 17;20(6):1664. doi: 10.3390/s20061664.
Moisture is one of the major causes of problems in buildings, and it can compromise their performance. Infrared thermography (IRT) is a non-destructive testing technology that can be used to assess the humidification phenomenon and, thus, prevent some of the problems caused by moisture. The images obtained by IRT reflect the thermal patterns of the surface under study and can be evaluated using a quantitative approach, which allows not only the traditional visualization of the thermal patterns but also quantification of surface temperatures and/or their differences. The relevance of this work is related to the discussion of the strengths and weaknesses of several methods to quantitatively assess the humidification phenomenon using IRT. For that purpose, the partial humidification by the bottom surface of a lightweight concrete specimen was considered as a case study. To evaluate the thermal gradients, the evolution of the thermal imaging throughout the measurement period and the definition of the areas particularly affected by moisture, a methodology that included a pre-processing phase for data reduction, followed by a data processing phase, were implemented. In the data processing, different statistical and numerical methods were tested. The results of the statistical descriptive analysis highlighted the time variation of the surface temperature, both when considering the entire specimen and when considering only specific areas. The variability of the temperatures at certain moments of the experiment could be observed in the box-plot representation. The image subtraction proved to be an interesting technique to quantify the temperature differences if the first image was used as reference. A thermal index, TI, was proposed to assess the cooling rate. The index highlighted the initial instant when the effect of moisture on the surface temperature was detectable.
潮湿是建筑物出现问题的主要原因之一，它会影响建筑物的性能。红外热成像（IRT）是一种无损检测技术，可用于评估加湿现象，从而防止一些由潮湿引起的问题。IRT 获得的图像反映了被测表面的热图案，可以使用定量方法进行评估，该方法不仅允许对热图案进行传统的可视化，还可以对表面温度及其差异进行量化。这项工作的相关性在于讨论了使用 IRT 定量评估加湿现象的几种方法的优缺点。为此，考虑了轻混凝土试件底面的局部加湿作为案例研究。为了评估热梯度，通过在整个测量期间对热成像的演变以及定义受湿气特别影响的区域，实施了一种包括数据减少预处理阶段和数据处理阶段的方法。在数据处理中，测试了不同的统计和数值方法。统计描述性分析的结果突出了表面温度的时间变化，无论是在考虑整个试件的情况下还是仅在考虑特定区域的情况下。在实验的某些时刻，可以在箱线图表示中观察到温度的可变性。图像相减被证明是一种量化温度差异的有趣技术，如果将第一幅图像用作参考。提出了一个热指数 TI 来评估冷却速率。该指数突出了表面温度可检测到湿气影响的初始瞬间。
