The Effect of Fiber, Opacifier Ratios and Compression Pressure on the Thermal Conductivity of Fumed Silica Based Vacuum Insulation Panels

Davraz M., Bayrakci H. C., YUSUFOGLU Y.

ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING, vol.41, no.11, pp.4263-4272, 2016 (SCI-Expanded) identifier identifier


Vacuum insulation panels (VIPs) provide high thermal resistances properties that can enhance the energy efficiency of the insulating systems and provide savings in energy consumption. They are generally made with porous core materials wrapped, under vacuum, in airtight barrier films. The properties of the core materials have big effect on the thermal insulation performance and mechanical properties of the VIPs. In this study, a novel VIP core formulation was developed by using a nano-powder, fiber and opacifier at different ratios. The VIP samples at various compression pressures with different vacuum levels were produced by using the obtained core formulations. Moreover, the relationship between compression pressure and density of VIP core samples was investigated; thermal conductivities of the samples were measured according to heat flow meter method at atmospheric and 0.1 mbar pressure levels. The findings were analyzed by using Datafit 7.1 software. As a result, the optimum fiber and opacifier ratio were determined as 13-20 and 15 %, respectively, for VIP prototypes obtained by using fumed silica (220 ), glass fiber (avg. diameter; ) and silicon carbide (575 ). Furthermore, the effect of fiber and opacifier ratios on the VIP core densities was investigated and various equations were developed to estimate the thermal conductivity values of VIPs at atmospheric and 0.1 mbar pressure levels.