Thermal performance evaluation of Calcium Silicate and Fumed Silica composite core materials for Vacuum Insulation Panels

Vacuum Insulation Panel (VIP), an advanced thermal insulation, offers considerably lower thermal conductivity values compared to traditional thermal insulation materials. However, high cost and considerable environmental impact originating from Fumed Silica core material limits widespread use of VIPs. This research experimentally investigates the thermal performance of Calcium Silicate and Fumed Silica composite as an alternative material suitable for VIP core. In this study VIP core samples (150 × 150 mm) were prepared consisting of different mass ratios of Calcium Silicate, Fumed Silica and glass fibre along with SiC as an opacifier. Thermal conductivity of core samples was measured using Heat Flow Meter. At atmospheric pressure, the average thermal conductivity of a 70% Calcium Silicate, 15% Fumed Silica, 5% glass fibre and 10% SiC opacifier core was measured to be 0.03745 W/mk. A VIP core composed of 40% calcium silicate, 45% fumed silica, 5% glass fiber and 10% SiC opacifier achieved a thermal conductivity of 0.03046 W/mK at atmospheric pressure. When the Calcium Silicate mass ratio was decreased to 25% in the sample and Fumed Silica ratio increased to 60%, 5% glass fibre and 10% SiC opacifier average thermal conductivity of the VIP core reduced to 0.02639 W/mK at atmospheric pressure. The VIP prototype produced using a composition of 25% calcium silicate, 60% fumed silica, 5% glass fiber, and 10% SiC opacifier demonstrated a thermal conductivity of 0.01449W/mK at pressure of 4 mbar. It is anticipated that further lowering the pressure to 0.5 mbar during VIP prototype fabrication could potentially lead to an additional reduction in thermal conductivity comparable to the thermal performance of a fully Fumed Silica core-based VIP.