Experimental investigations into thermal transport phenomena in vacuum insulation panels (VIPs) using fumed silica cores

• Experimental and theoretical characterisation of VIP thermal conductivity.
• Measured effect of opacifiers on radiative thermal conductivity of VIP core.
• Manufactured VIPs achieved an overall thermal conductivity of 3.7 mW m−1 K−1.
• VIP overall thermal conductivity measured using guarded hot plate apparatus.
• Larger VIPs expected to have centre of panel thermal conductivity of 3 mW m−1 K−1.

This paper reports the experimental and theoretical evaluation of various heat exchange phenomena that occur in a vacuum insulation panel (VIP). Fumed silica and a range of IR-opacifiers were mixed in different proportions to identify the best composition that yields minimum thermal conductivity value at ambient and evacuated conditions. Three variants of carbon black (CB) and one each of silicon carbide (SiC) and titania (TiO2) were employed as opacifiers. Of all tested, CB was found to be the best opacifier based on the detailed experimental FTIR investigations performed whereby specific extinction was measured for each composition. To demonstrate the performance of the optimised samples of core materials developed four VIPs were manufactured which achieved a significantly low overall VIP thermal conductivity of <4 mW m−1 K−1 (R-value > 36.03 ft2 ̊F h/BTU in.) measured using guarded hot plate apparatus. With these thermal conductivity values the samples perform much better than most state of the art commercially offered VIPs.