Experimental characterisation and evaluation of the thermo-physical properties of expanded perlite—Fumed silica composite for effective vacuum insulation panel (VIP) core

• Published in: Energy and buildings 2014-02, Vol.69, p.442-450
• Main Authors: Alam, M., Singh, H., Brunner, S., Naziris, C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building insulation; Buildings; Buildings. Public works; Exact sciences and technology; Expanded perlite; External envelopes; Fumed silica; Materials; Miscellaneous (including polymer concrete, repair and maintenance products, etc.); Pore size distribution; Radiative conductivity; Strength of materials (elasticity, plasticity, buckling, etc.); Structural analysis. Stresses; Thermal conductivity; Thermal insulation; Vacuum insulation panel
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2013.11.027

•Experimental characterisation of expanded perlite-fumed silica composite as cheaper VIP cores.•Measured effect of expanded perlite on opacifying properties of VIP core.•Measured thermal conductivity of VIP core at different pressures.•Measured radiative conductivity of VIP core using FTIR technique.•Measured gaseous conductivity of VIP core using pore size from mercury intrusion and N2 sorption. The thermo-physical properties of expanded perlite-fumed silica composites were experimentally investigated as an alternative lower cost material for vacuum insulation panel (VIP) core using expanded perlite as a cheaper substitute of fumed silica. Pore size analysis was carried out using nitrogen sorption technique, mercury intrusion porosimetry and transmission electron microscopy and average pore size was estimated to be in the range of 50–150nm. VIP core board samples measuring 100mm×100mm and consisting of varying proportions of expanded perlite, fumed silica, silicon carbide and polyester fibre in the composite were prepared. The centre of panel thermal conductivity of the core board containing expanded perlite mass proportion of 60% was measured as 53mWm−1K−1 at atmospheric pressure and 28mWm−1K−1 when expanded perlite content was reduced to 30%. The centre of panel thermal conductivity with 30% expanded perlite content was measured as 7.6mWm−1K−1 at 0.5mbar pressure. Radiative conductivity of the composite with expanded perlite mass of 30% was measured to be 0.3–1mWm−1K−1 at 300K and gaseous thermal conductivity 0.016mWm−1K−1 at 1mbar, a reduction of 8.3mWm−1K−1 from the value of gaseous thermal conductivity at 1atm pressure. Opacifying properties of expanded perlite were quantified and are reported. A VIP core cost reduction potential of 20% was calculated through the use of expanded perlite in VIP core.