Vacuum Insulation Panel Production with Ultralow Thermal Conductivity—A Review

Vacuum insulation panel (VIP) is becoming the main resource of thermal insulation material, which has been widely applied in the recent decades. Varies of core material and sealing method have been developed for VIP applications, typically achieving thermal conductivity below 5 mW/mK. To further decrease the thermal conductivity of VIP, the in-depth understanding of the heat transfer mechanism via different components (e.g. core material conduction, gaseous conduction and thermal radiation) is highly necessary. There are reported experimental and modeling works focusing on individual components involved in VIP, but a comprehensive and summative study combining different factors is still missing. Furthermore, most of researches on VIP study the long-term performance evolvement, while initial conductivity, especially in ultralow conductivity region, is less studied but more scientifically interesting. In this work, the existing works on the analytic model of VIP are reviewed and the quantitative comparison between the different contributions to the overall thermal conductivity is presented. This work aims at the low initial conductivity condition and discusses the possible technical routes to further decrease the initial conductivity. The tools provided here will contribute to the future VIP design using novel core materials and manufacturing techniques, to achieve ultralow thermal conductivity.