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Determination of Optimum Drying Condition of VIP Core Material by Wet Method

Li, Cheng-Dong, Chen, Zhao-Feng, Boafo, Fred Edmond, Chen, Qing, Zhang, Juan, Zhou, Jie-Ming, Ye, Xin-Li, Li, Chen-Yang
Drying technology 2013 v.31 no.10 pp. 1084-1090
drying, fiberglass, insulating materials, microstructure, thermal conductivity, thermogravimetry
Vacuum insulation panel (VIP) core materials were successfully fabricated by wet method. The phase composition, microstructure, and thermal conductivity of VIP core materials were investigated. The density of VIP core materials was 176 kg/m³, while the mean thermal conductivity of VIP core materials was about 31 mW/(m · K). The mean thermal conductivities of VIPs were 2.78 mW/(m · K), 2.62 mW/(m · K), 2.47 mW/(m · K), 2.5 mW/(m · K), and 2.4 mW/(m · K), which correlated to VIP core materials that had been dried at 150°C for 30 min, 60 min, 90 min, and at 170°C for 30 min and 60 min, respectively. However, the mean thermal conductivity evaluated for VIPs with core material that had not been dried was 3.0 mW/(m · K). The thermal conductivity of VIPs with core material that had been dried reached a maximum on the third day and tended to be a steady value with time, whereas the one with core material that had not been dried recorded a high thermal conductivity value and continued to rise in a fluctuating pattern with time. According to the result of the thermogravimetric curve, drying at 150°C for 60 min showed characteristics of complete drying. In addition, the thermal conductivity of VIPs at this drying condition was low and stable. Theoretical and experimental analysis showed that the optimum drying condition for fiberglass VIP core materials was drying at 150°C for 60 min.