Experimental determination of the effective thermal conductivity of Vacuum Insulation Panels at fire temperatures

In this study, the effective thermal conductivity of a commercial Vacuum Insulation Panel (VIP) at temperatures up to 900 degrees C is experimentally determined. An experimental setup, based on the Heat Flow Meter Apparatus (HFMA) method, is designed and realized. Two commercially available VIPs (each 20mm thick) are joined together to form a specimen, which is subjected to fire conditions from one side, while the other side is at ambient conditions. The temperatures on both sides of the specimen and the heat flux on the unexposed side are recorded. The experimental data are coupled with a numerical model, which takes into account the one dimensional steady state heat transfer through the thickness of the specimen and the detailed heat transfer mechanisms for the effective thermal conductivity of the VIP. Gas, solid and radiation conduction mechanisms are considered and their parameters are defined through an optimization technique. The defined optimized values are found to lie between the respective values reported in the literature. The contribution of each heat transfer mechanism to the overall effective thermal conductivity is also discussed. The paper provides a generalized methodology for the estimation of the effective thermal conductivity of VIPs from ambient to fire temperatures. Copyright (c) 2016 John Wiley & Sons, Ltd.