Cold chain & HACCP: temperature monitoring for optimal food safety
5 November 2024 by Edina GÁLFI
Transporting temperature-sensitive goods : moving towards self-contained cold logistics
22 February 2024 by Edina GÁLFI
Self-contained cooling is a term you often hear used to talk about an independent cold source that operates without any additional energy input (mains power supply, battery, fuel, etc.).
The cold is transferred by natural convection. No fans are necessary.
Transporting temperature-sensitive goods with a self-contained cold solution means that you also need some form of insulated infrastructure in a format suited to the volume to be transported. In addition, using a passive cold/insulated container ecosystem makes it easy to avoid transporting and cooling empty volumes.
Self-contained cooling: active or passive cooling ?
Self-contained cooling refers to passive cooling as opposed to active cooling.
The latter is generated by a mechanical or electric cooling system, which cannot operate without an external energy source. Costly and energy-intensive, a ventilated active cooling system is also heavy. It adds to the weight of the goods transported themselves.
Today there are two passive cooling systems that can be used to transport temperature-sensitive goods.
The choice of which one to use will depend on the daily quantities volumes involved, the existing infrastructure and the customer’s logistics organisation.
Which cold source to use ?
Eutectic plates
Eutectic plates are rotational or injection moulded cases containing a non-toxic eutectic solution made up of water, mineral salts and cooling media. These reusable devices diffuse the cold based on the phase change principle: they change from the liquid to the solid phase when they are prepared, and the reverse occurs as they release the accumulated frigories.
This change of phase occurs when the eutectic solution reaches its melting point. The melting point of water is 0°C, while that of eutectic substances depends on the concentration of mineral salts. This concentration of mineral salts therefore varies according to the target cooling temperature.
The target temperature of eutectic plates is closely linked to the issues in foodstuff distribution and the regulations in force concerning the storage of perishable goods. The eutectic threshold will therefore be different for:
- Chilled goods: +2°C/+4°C or +2°C/+8°C
- Frozen goods: -20°C
- Ambient goods: +15°C/+25°C
Use in cold logistics: Eutectic plates are the preferred solution for small and medium-sized firms.
CO2
CO2, commonly known as dry ice, lends itself particularly well to transporting foodstuffs. Its thermal efficiency makes it the perfect ally of logistics operators in every sector. Reminder: one kilo of dry ice lowers the temperature of 10 litres of water by 15°C.
The lack of residue once the cold source has evaporated is also a noteworthy advantage in cold production. Indeed, logistics and other operators have no cold sources to handle when their goods are delivered.
Finally, solid CO2 is produced from the emissions of the chemical industry and therefore not only constitutes recycled waste but also contributes to the circular economy.
Dry ice snow
Dry ice snow is the solid form of carbon dioxide as conventional snow is that of water. It is called dry ice as it contains no moisture. Unlike water, CO2 melts at -56.6°C and sublimates – i.e. turns from solid to gas – at -78.5°C.
Dry ice snow or carbon dioxide snow is therefore produced by discharging liquid CO2 stored at -20°C and 20 bar through an expansion valve. This expansion turns the CO2 in a liquid state into a solid.
Use in cold logistics: Depending on the insulation technology chosen, it is perfectly possible to use it to keep both frozen and chilled goods at the right temperature.
Dry ice snow is the cold source used by our SIBER and MINICRYO technologies.
Dry ice: blocks, sticks or pellets
Dry ice is made from carbon dioxide snow. Pellets are produced by compressing the snow in a pelletiser. They can be of different sizes depending on their use (3 mm, 5 mm, etc.), just as dry ice blocks and sticks also be made in different sizes.
Use in cold logistics: loose in a dry ice drawer or in hermetically sealed bags, dry ice is mainly used to transport frozen goods.
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