C009 -- Determination of Vacuum Insulation Panel Edge-Loss and R-Value

Vacuum insulation panels (VIPs) with high thermal resistivities, RSI*, provide insulation needed for zero-energy buildings without loss of interior space. VIPs have center-of-panel thermal resistivities that routinely exceed 173 m∙K/W, the "Super-insulation" threshold. The heat flux through the core and enclosure materials due to an imposed temperature difference is the starting point for the determination of the "Effective Panel RSI-value" (panel RSI-value). The final evaluation of the Effective Panel RSI-value requires a correction for the heat flow around the edges of the panel through the relatively high thermal conductivity enclosure. The impact of the thermal properties of the enclosure and core materials on the effective R-value have been evaluated for numerous assemblies using finite element modeling. The result is a correlation for the effective panel R-value based on center-of-panel measurements. The finite element evaluation validates a simplified calculation of the ratio (Panel RSI)/(COP RSI) that can be used for a range of practical panel designs. The correlation gives (Panel RSI)/(COP RSI) as a function of the ratio of edge properties to core properties (θ). Consideration has also been given to the selection of enclosure materials, primarily the high thermal conductivity component, usually a metallic foil and the impact of heat flux transducer dimensions. The resulting correlation expedites the optimization of vacuum panel design with respect to life-time and thermal resistance. Numerical simulation results and the correlation that has been developed are discussed in this paper.

Keywords: Vacuum insulation panel (VIP); vacuum insulation panel number (VIPN); edge losses, thermal bridging; center-of-panel RSI-value; effective panel RSI-value, thermal resistance, thermal resistivity