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Ask the Produce Docs (General)

How can I calculate the amount of dry ice needed to keep my product frozen in transport?

Category
  • Cold Chain
  • Transportation
Question

We are being asked to airship about 500 Kg of a frozen item.  Is there any information publication that talks about how much dry ice will keep the product frozen?  There are recent limitations on dry ice usage so I wonder if this will be a problem. The flight itself is only about 1.5 hours but let's assume cargo has to be brought to the airport 4 hours before, and it takes another 4 hours to get out, so assume 10-12 hours is the time needed from freezer to freezer. (C.)

Answer

It is possible to estimate the amount of dry ice needed.  One Kg of dry ice produces 614 kJ of cooling effect as it sublimates.  The amount of dry ice needed will be equal to the amount of heat that penetrates the package.  This will be an estimate based on product temperature, outside temperature and humidity, time the box is exposed directly to the sun, and insulation level of box (insulation is recommended). 

Another option is to set up an experiment.  Pack a typical box with product and a generous amount of dry ice. Weigh the ice just before packing.  Then put the box in an environment that simulates the extreme conditions that may be encountered in a commercial trip and leave it there for the duration of a typical trip.  Weigh the remaining dry ice at the end of the simulated trip. The difference in weight is the amount of dry ice needed.

Jim Thompson

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