Hygrothermal modeling and evaluation of freeze-thaw damage risk of masonry walls retrofitted with internal insulation
Hygrothermal modeling and evaluation of freeze-thaw damage risk of masonry walls retrofitted with internal insulation
复制标题
内保温改造砌体墙体湿热模拟及冻融破坏风险评估
DOI：
10.1016/j.buildenv.2017.08.001
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发表时间：
2017
影响因子：
7.4
通讯作者：
J. Carmeliet
中科院分区：
文献类型：
--
作者：
Xiaohai Zhou;Xiaohai Zhou;D. Derome;J. Carmeliet;J. Carmeliet
对于具有保值外观的历史建筑，内墙保温是提高建筑能源效率的唯一可能解决方案。然而，内部保温层的应用显著改变了建筑围护结构的湿热性能。对于砖石墙，这种干预可能导致砖墙的冻融破坏。在本研究中，建立了一个湿热模型。该模型考虑了多孔介质中水分和热量的传递，跟踪了孔隙大小分布和含冰量对冻融过程的影响。水在多孔介质中的冻结和融化是基于冰点下降理论实现的，因为水在多孔介质中的冻结温度取决于孔隙大小，即。小孔隙中的水在温度低于0℃时结冰。数值模拟结果与多孔介质冻结实验结果吻合较好。传统的湿热评估使用摄氏温标上过零度的次数作为冻融循环的次数。我们提出了一种方法，该方法使用实际冰生长和融化循环的数量作为更准确地说明冻融过程的指标。此外，我们还开发了一个称为FTDR指数的指数来评估冻融损害风险。我们使用两种瑞士气候条件对未隔热和内部改造的砖石墙进行了模拟。研究清楚地表明，在两种气候条件下，内部改造后的冻融循环和冰含量都有所增加。因此，内部改造后的FTDR指数增加。
For historical buildings with a worth-preserving appearance, internal wall insulation can be the only possible solution to improve the building energy efficiency. However, the application of an internal insulation layer changes significantly the hygrothermal performance of the building envelope. For masonry walls, such intervention may lead to freeze-thaw damage of the brickwork. In this study, a hygrothermal model is developed. The model takes into account moisture and heat transport in porous medium and tracks the occurrence of freezing and thawing in function of pore size distribution and as well as the ice content. Freezing and melting of water in porous medium is implemented based on the theory of freezing point depression, as freezing temperature of water in porous medium depends on pore size,i.e.water in the smaller pores freezes at temperatures lower than 0 °C. The numerical model results are compared with a porous medium freezing experiment and good agreement is found. Traditional hygrothermal assessment uses the number of zero crossings on a Celsius scale as the number of freeze-thaw cycles. We propose a method that uses the number of actual ice growth and melt cycles as an indicator more accurately accounting for the freeze-thaw process. In addition, we develop an index, called FTDR Index, to assess freeze-thaw damage risk. We perform simulations of uninsulated and internally retrofitted masonry walls using two Swiss climatic conditions. The study clearly shows increase of freeze-thaw cycles and ice content after internal retrofitting in both climates. Thus, FTDR Index increases after internal retrofitting.