PartagerICR2011 highlights: improving insulation thanks to vacuum
Vacuum insulated panels (VIPs) are a new technology which is theoretically 5 times less conductive than classic polyurethane panels (3 times less in practice because of the various thermal bridges).
Vacuum insulated panels (VIPs) are a new technology which is theoretically 5 times less conductive than classic polyurethane panels (3 times less in practice because of the various thermal bridges).
Vacuum insulation panels are currently being launched in many insulation applications: aeronautics, marine, building, domestic/commercial refrigeration and insulated containers for the transport of heat-sensitive products such as vaccines, blood and medicines.
Conventional insulation materials rely on gas captured in very small closed cavities using a minimum amount of material (or very high porosity above 90%). The main contributor to heat transfer is the captured gas, generally air, which has a thermal conductivity of 0.025 W/m.K. Therefore the most efficient solution for reducing heat transfer is to remove the gas through a vacuum or by applying low pressure, as in the case of a Thermos flask.
A VIP has a porous core material (fibrous filler, fibreglass, open polymer foams, pellets, “pyrogenated” silica which has the advantage of a certain amount of nanoscopic pores increasing the durability, etc.) wrapped in a water-tight film. VIPs are made by sealing the core material in a barrier film under vacuum. The film is generally a polymer-aluminium-polymer multi-layer material which must prevent penetration of air components in the material, specifically nitrogen and oxygen and above all water vapour. In order to achieve and maintain low thermal conductivity, the core material, the quality of the barrier film and the vacuum level are the main parameters but are not sufficient: for instance, efficient VIP boxes can be obtained with fibreglass and silica, but for both materials, the barrier film must be carefully selected and validated, according to the core material and to the required vacuum level. (Fibreglass requires a vacuum level as low as 10-6 bar at least and hence a resistant enough barrier film). Containers should also be well designed so as to avoid thermal bridges.
VIPs can increase the thermal performance of insulated containers (up to 240 hours) and/or reduce their thickness. VIP refrigerated containers allow for controlled-temperature shipping lasting 7-10 days as their performance is 3 times better than conventional polyurethane (up to 96 hours) and consequently 4.5 times higher then that of polystyrene (48 hours). According to Kacimi and Labranque, their success requires improvements in efficiency and lower costs, for instance simply thanks to a protective layer with a resistant material. The re-use of the insulated boxes will also make them profitable and justify their high price.
Vacuum Insulated Panels (VIP) in insulated packaging, Kacimi et al.
Vacuum insulation panels are currently being launched in many insulation applications: aeronautics, marine, building, domestic/commercial refrigeration and insulated containers for the transport of heat-sensitive products such as vaccines, blood and medicines.
Conventional insulation materials rely on gas captured in very small closed cavities using a minimum amount of material (or very high porosity above 90%). The main contributor to heat transfer is the captured gas, generally air, which has a thermal conductivity of 0.025 W/m.K. Therefore the most efficient solution for reducing heat transfer is to remove the gas through a vacuum or by applying low pressure, as in the case of a Thermos flask.
A VIP has a porous core material (fibrous filler, fibreglass, open polymer foams, pellets, “pyrogenated” silica which has the advantage of a certain amount of nanoscopic pores increasing the durability, etc.) wrapped in a water-tight film. VIPs are made by sealing the core material in a barrier film under vacuum. The film is generally a polymer-aluminium-polymer multi-layer material which must prevent penetration of air components in the material, specifically nitrogen and oxygen and above all water vapour. In order to achieve and maintain low thermal conductivity, the core material, the quality of the barrier film and the vacuum level are the main parameters but are not sufficient: for instance, efficient VIP boxes can be obtained with fibreglass and silica, but for both materials, the barrier film must be carefully selected and validated, according to the core material and to the required vacuum level. (Fibreglass requires a vacuum level as low as 10-6 bar at least and hence a resistant enough barrier film). Containers should also be well designed so as to avoid thermal bridges.
VIPs can increase the thermal performance of insulated containers (up to 240 hours) and/or reduce their thickness. VIP refrigerated containers allow for controlled-temperature shipping lasting 7-10 days as their performance is 3 times better than conventional polyurethane (up to 96 hours) and consequently 4.5 times higher then that of polystyrene (48 hours). According to Kacimi and Labranque, their success requires improvements in efficiency and lower costs, for instance simply thanks to a protective layer with a resistant material. The re-use of the insulated boxes will also make them profitable and justify their high price.
Vacuum Insulated Panels (VIP) in insulated packaging, Kacimi et al.