Cold Chain Design for Frozen Products

A successful cold chain company knows how to efficiently transport frozen products from the source to the destination while complying with all standards. In cold chain applications, maintaining the required temperature is the most important challenge.  Without that assurance the the quality of the product can be damaged.

In order to transport temperature sensitive products and maintain their integrity, supply chain solution providers should have well designed and documented processes from pre-shipment preparation to final verification and delivery to destination. The design of an efficient cold chain packing process should contain three steps.

Identify the appropriate cold chain materials. The most used refrigerant for passive cold chain packing systems are the water-based ones, however this is not a good solution to keep the product temperature under 0°C. This is because any small temperature variance within the container can cause the product to rise above 0°C. To keep the item temperature below 0°C, a different type of refrigerant should be used. Basically the product category will dictate the material to be used, however there is one to rule to follow when testing the refrigerant and that is to precondition them at least 10°C below the phase point.  For example most designs for transport that take less than two days will use expanded polystyrene (EPS) containers. Two or three day transports will use polyurethane (PUR) containers. For durations beyond three days you should consider using Vacuum Insulated Panels (VIP).

Identify the optimal configuration. In the majority of cases the most efficient design is to place frozen refrigerants below and above the products. It is important to have more gel packs above the payload because the cold dense air created by the refrigerant will always flow down. Another important design aspect is the air flow within the packing configuration. You must ensure that cold air from the top frozen gels can circulate to the product load below.

Test and document the successful solution. Although you must test the cold chain shipping configuration in both summer and winter conditions, usually the tests are not done in the winter if the summer tests were successful. One important aspect of testing is to place the temperature measurement probes on the top corners of the package because this area will always be the location of the highest product temperatures at the end of the thermal test.

Deciding upon the best container material (whether EPS, PUR or VIP) and identifying the suitable amount of refrigerant is vital in creating a successful packing configuration. When assessing a cold chain design for frozen products, it is best to focus the temperature measurement on the top corners of the product load. In order to maximize the phase change of the PCMs from solid to liquid and therefore keeping the product load in the required temperature range attention needs to be given to the container’s thermodynamics.

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