Simultaneous test and visual identification of heat and moisture transport in several types of thermal insulation

• Published in: Energy (Oxford) Vol. 197; p. 117137
• Main Authors: Guo, Haijin, Cai, Shanshan, Li, Kun, Liu, Zhongming, Xia, Lizhi, Xiong, Jiazhuang
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.04.2020; Elsevier BV
• Subjects: Aerogel blanket; Aerogels; Building envelopes; Cooling effects; Envelopes; Foams; Heat conductivity; Heat transfer; Hygrothermal properties; Identification methods; Insulation; Magnetic resonance imaging; Moisture content; Organic foam; Phenolic compounds; Phenols; Pinholes; Plastic foam; Scanning electron microscopy; Simultaneous test; Thermal conductivity; Thermal insulation; Thermal utilization; Transport path; Variation; Visual identification; Water content; Aerogel blanket; Transport path; Simultaneous test; Hygrothermal properties; Visual identification; Organic foam
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2020.117137

The utilization of thermal insulation is one of the most effective methods to reduce the heating and cooling loss through building envelopes. However, moisture ingress driven by the pressure gradient across the insulation may lead to a variation of the effective thermal conductivity, which highly deteriorates the thermal performance of building envelopes. In order to investigate moisture transport mechanism and its impact on the heat transfer procedure, a novel simultaneous test method based on the modified guarded hot box is proposed to investigate the variations of the moisture content and the effective thermal conductivity of thermal insulation, besides, several possible visual identification methods are applied to analyze the moisture transport paths. Based on the proposed methods, both aerogel blanket and organic foam are investigated on the variations of hygrothermal properties. Results indicate that compared to the foam insulation, the moisture content has a greater impact on aerogel blankets with the thermal conductivity increase to 3 times of the initial values. Both scanning electron microscopy (SEM) combined with crystal tracer and magnetic resonance imaging (MRI) are utilized to identify the moisture transport paths of phenolic and polyisocyanurate foams. Pinholes and capillary channels are two main paths for liquid permeation into phenolic. •Propose a simultaneous test method to measure the heat and moisture transfer.•Analyze the hygrothermal performance based on the material structure.•Visualize the moisture transport paths in typical thermal insulation for the first time.•Pinholes and capillary channels are main paths for liquid water to permeate into phenolic.