The storage and transport of COVID-19 vaccines has to be managed in a cold chain, with the first approved vaccine by Pfizer-BioNtech requiring storage temperatures of -70 C. Besides using dry ice (solid carbon dioxide at -75.8 C), Vacuum Insulated Panels and vacuum insulation have become attractive solutions.
Picture 1: COVID-19 vaccine production. Source: https://www.pfizer.de/covid-19-spezial
Vacuum Insulated Panels for Transport of COVID-19 Vaccine
Thermal packaging containers for medical equipment use evacuated double-walled panels. At pressures below 1 mbar, the convection and heat conduction of the residual gas becomes very low. The double-walled casing has to be leak-tight and can be made of metal or metallised plastic. The metallisation reduces heat emission — which is similar to what occurs in thermos flasks.
For mechanical stability under vacuum, a filling is required. Often, this filler is made of small Perlite spheres, which is a material produced from volcanic rock with a very low thermal conductivity. These special getter materials can help keep the vacuum functioning for decades. In combination with low vacuum pressure, thermal conductivity of the Vacuum Insulated Panel becomes as low as 0.006 W·m−1·K−1. This improves insulation by 10 to 20 times, and is more efficient than other materials, such as polystyrene foam.
Picture 2: Example of an international shipping container for temperature-sensitive medical equipment. Courtesy of va-Q-tec AG, Wuerzburg, Germany. https://va-q-tec.com
The evacuation in large-scale production is typically done by dry compressing screw pumps in combination with roots pumps. Dry screw pumps are preferred as they can tolerate the small amounts of Perlite powder (which could be entrained into the vacuum pump). In oil-sealed pumps, the oil would have its lubrication properties degraded by the powder.
Related: For further information on screw pumps and oil-sealed pumps, we’ve created a comprehensive resource that explores the science behind vacuum pumps.
Picture 3: Series production of Vacuum Insulated Panels. Courtesy of va-Q-Tec AG, Germany.
Besides healthcare and logistics, Vacuum Insulated Panels are also used in the food industry and for the thermal insulation of buildings. In building construction, the Vacuum Insulated Panels are applied in low-energy buildings and for renovations where there isn’t enough space for conventional insulation.
For further information on Vacuum Insulated Panels and how they help with the storage and transport of COVID-19 vaccines, please contact us.
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