Cryogenic refrigeration

Cryogenic refrigeration

The power of cold for low temperature

Cryogenic refrigeration for insulated containers means using dry ice as a cooling agent.

Because it sublimates at -78.5°C, dry ice is a powerful refrigerant mainly used to transport frozen goods.

Dry ice is frozen carbon dioxide and takes its name from the fact when it evaporates it turns directly from solid to gas. Dry ice does not produce water, it sublimates.

Dry ice is used in different forms: blocks, slices, slabs, pellets, rice-grain pellets and snow.

How to determine the quantity of dry ice needed in an insulated container? Contact us and we will calculate the weight of refrigerant for you, based on the insulated contained to be used and the transport time envisaged.

Dry ice

Dry ice is a solid form of carbon dioxide that comes in blocks, slabs, sticks, pellets, etc. It has a negative temperature of -78.5°C and as it sublimates it releases frigories, without leaving any residue.

 

The cooling capacity of dry ice is much greater than that of eutectic plates.
This cooling capacity makes it the ideal refrigerant for low temperatures and frozen goods. OLIVO does not recommend the direct use of dry ice to transport chilled goods that would be degraded by freezing.

Where to place the dry ice ?

The dry ice must be placed in the top of the insulated container, if possible above the load of frozen goods.
OLIVO insulated containers can be fitted with a metal drawer (optional equipment) containing the dry ice and diffusing the cold in a homogeneous way.
OLIVO insulated containers have grooves on the inside walls that serve to optimise the natural convection and allow the cold air coming from the sublimation of the dry ice to circulate around and through the load being transported.

 

For products needing to be kept at a very low temperature such as lactic ferment, it is recommended that the dry ice be placed within the load: this is the “layer cake” technique, which alternates layers of goods with layers of dry ice.
Apart from the specific technique, we do not recommend placing dry ice directly in the load. The goods in contact with the dry ice would be unnecessarily very cold while the temperature of other parts would rise because they were poorly irrigated by the cold gas.

Quantity of dry ice

When frigories are released inside an insulated container the aim is to maintain the inner temperature for longer, namely for the duration of the transport. What weight of dry ice is needed?

 

OLIVO can provide you with a chart giving the weight of dry ice required to achieve the desired result according to the ambient temperature and the transport time. The energy input in the form of dry ice must be sufficient to compensate the heat entering the insulated container during transport.

Safety

Dry ice is neither toxic nor inflammable. It is low risk as long as you are familiar with its properties.

 

Dry ice is extremely cold (-78.5°C). If it comes into direct contact with the skin it can cause burns (frostbite). It is therefore essential to wear protective cryogenic gloves and safety glasses.

 

Dry ice is made from CO2 gas and when it vaporises it gives off CO2, which is a colourless, odourless and tasteless gas.
CO2 gas is approximately 1.5 times heavier than air. It spreads along the ground and can accumulate there. Dry ice must therefore be stored and used in a well-ventilated workspace.

 

CO2 has a narcotic effect, which means that it can cause loss of consciousness when its concentration in the air we breathe exceeds 7%. There is a risk of asphyxia above a concentration of 8%. Inhaled air contains 0.035% CO2.

 

When emptying a container refrigerated with dry ice, in a retail outlet for example, it is important to open the container in a well-ventilated place. When the container is opened, the CO2 gas produced by the sublimation of the dry ice must be able to dissipate into the atmosphere rather than stagnating in a confined, poorly ventilated space.

ADR marking

In Europe, the road transport of dangerous goods is covered by the European Agreement concerning the International Carriage of Dangerous Goods. This agreement is known as the ADR.

 

Dry ice can create a dangerous atmosphere. Insulated containers with a capacity of more than 1.3 m3 must have specific transport marking indicating the presence of dry ice. These may be BAC type insulated containers used to deliver CO2 (full load) or ROLL containers refrigerated with dry ice (refrigerating quantity).

 

The ADR marking is intended to indicate the presence of dry ice and raise transport chain users and operators’ awareness of the safety precautions.
ADR marking is required if:

  • You are using an insulated BAC to transport dry ice. In this case, the dry ice is considered as a conditioner within the meaning of the ADR.
  • You are using a ROLL insulated container refrigerated by dry ice. In this case, the dry ice is considered as a coolant within the meaning of the ADR.

You can download OLIVO’s summary on the ADR marking requirements.
Remember that you will need to check what the marking requirements specific to your country are. The text of the ADR can be downloaded from the UNECE website.

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