VIPs – or vacuum insulation panels – are flat panels for optimised temperature insulation that are based on the principle of the thermos flask. These panels offer unrivaled heat insulation at minimum thickness.
The pressure-resistant core material consists of a compressed plate of micro-porous powder. The core is evacuated and sealed in a high-barrier film using a special technique. The specialist foil used in the manufacture of VIPs also offers protection against air or water intrusion.
VIPs offer ten times higher thermal insulation than traditional insulation materials of the same thickness. Example: 2 cm of VIP insulation will replace 20 cm of fibre or foam insulation. VIPs also offer a service life of up to 50 years. Fridges equipped with our VIPs use up to 50% less electricity, and containers with VIPs provide up to five days of constant temperature for heat or cold-sensitive cargo – without any external power supply. Using VIPs in new building construction or in refurbishment will significantly reduce heating costs and therefore improve the carbon footprint.
VIPs are used wherever precise heat insulation is required but the available space is limited. The innovative and eco-friendly VIPs by va-Q-tec AG are used in thermal packaging for the pharmaceutical sector, in fridges and freezers, buildings, technology and industry, and in the automotive and aviation sectors.
The life time of vacuum insulation panels depends on the characteristics of the film, the size of the pores of the core materials and on the thickness of the panel.
The film of the VIPs drastically reduces the transmission of water vapour and air. A good barrier against penetrating gases is an aluminium laminated film. This however causes heat leaks at the VIP edge and thus is only suitable for large vacuum insulation panels.
Metallized film, i.e. a very thin Al-layer within a high barrier film avoids these heat bridges. Micro-porous Silica has the smallest pore size.: smaller than 0.5 µm. Thus the thermal conduction of air is partially suppressed even at ambient gas pressures.: At a gas pressure of 100 mbar the thermal conductivity of a Silica VIP is only 0.007 W/mK. A totally aired (1000 mbar) va-Q-vip has a thermal conductivity of 0.020 W/mK, which is the worst case.
Long term investigations with 20 mm thick micro-porous Silica VIPs, which were wrapped into a metallized high barrier film, show that the gas pressure at ambient temperatures does not rise more than 1 mbar per year.(see Fig. 3)
That means the increase of the gas pressure after 50 years is about 50 mbar. This corresponds to a rise of the thermal conductivity to a maximum of 0.008 W/mK. That means, that the life time of a 20 mm thick VIP can be up to 30 years. A dry ambient condition for the VIP is very important, because high humidity can influence the film of VIPs.
Accordingly the life time of a 10mm VIP is reduced to half the time compared with a 20 mm VIP. For 40 mm VIPs the life time is doubled.
For quality control and development of advanced products it is not only necessary to know the actual gas pressure within the VIP but it is also important to measure the change of gas pressure.
Previous measurements took a long time to get reliable results. Therefore va-Q-tec has developed several methods which allow to obtain information on the increase of gas pressure within a short time and thus to perform accelerated ageing tests.
In even a shorter time it is possible to reduce the increase of gas pressure by accurate thermal conductivity measurements of a VIP-sample containing a special core material. From the known relation between the thermal conductivity and the gas pressure of the core material the gas pressure increase can be calculated. An example with VIP containing a special core material and wrapped in a metallized film cover is shown in Fig. 4. Here the measurement took just one day and a clear increase of thermal conductivity, which is proportional to the increase of gas pressure, can be seen.
These methods help va-Q-tec to control the barrier properties of delivered films, the gas pressure of any produced VIP and to develop new kinds of vacuum insulation products.