Thermal Performance
Heat transfer through a volume occurs by three modes: convection, conduction and radiation. Creating a vacuum practically eliminates convection, since this relies on the presence of gas molecules able to transfer heat energy by bulk movement through the insulator. It also greatly reduces conduction, as there are far fewer collisions between adjacent gas molecules (or between gas molecules and atoms of the core material).
Since the core material of a VIP is similar in thermal characteristics to materials used in conventional insulation, VIPs therefore achieve a much lower thermal conductivity (k-value) than conventional insulation, or in other words a higher thermal resistance per unit of thickness. Typically, commercially-available VIPs achieve a thermal conductivity of 0.004 W/(m·K) across the centre of the panel, or an overall value of 0.006-0.008 W/(m·K) after allowing for thermal bridging (heat conduction across the panel edges) and the inevitable gradual loss of vacuum over time.
Read more about this topic: Vacuum Insulated Panel
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