A company importing pharmaceuticals requested a consultation from the HILGRUP company. Some groups of drugs require specific temperature conditions while being transported and without auto refrigerators the shipment becomes an issue. The customer had a solution in a form of a foamed polystyrene container using dry ice as cold accumulator; however, it needed to be proved effective before mass production.

HILGRUP professionals have offered a complex solution to the problem including initial calculations and modeling, trial run, and final solution optimization.

Stage 1. Initial calculations and problem detecting

Initial calculations were made considering the container’s geometry, physical properties of the materials used and thermodynamic equations. Below is the list of starting values used as initial data for the calculations considering the customer’s requirements:

  • Overall container dimensions as shown on Pic.1;
  • Material of the container: foam plastic (density 25 kg/m3, thermal conductivity 0,039 W/(m*K);
  • Required temperature range inside the container: +2…+8° С;
  • Extreme temperature range inside the container: +1…+15° С;
  • Cold source (cooling agent) – dry ice;
  • Outside temperature: + 22° С…+ 27° С;
  • Maximum load of dry ice into container – 50 grams;
  • Transportation time: 20-24 hours.^1C53CA11238D79BE293B0C66DFF771E278BA77EB90147853E7^pimgpsh_fullsize_distr

However, the very beginning of the calculations showed that with dry ice as a cooling agent it is impossible to maintain the required temperature range within required time.

It was discovered that dry ice was evaporating too quickly, leading to extreme cooling of pharmaceuticals inside the container and decrease in temperature maintenance time from required 20-24 hours to 5 hours only.

Thus another solution was needed.

Stage 2. Modeling, test calculations, and solution validation.

HILGRUP professionals have designed a thermodynamic model of the container and performed computer simulation of temperature parameters within the container with a given outside temperature using special software. A number of test calculations were performed on the model using various combinations of container’s geometry and cooling agent. In the course of analysis, a suitable cooling agent was detected, which supposedly was capable of maintaining the temperature range during the whole period of time. It turned out to be water solution of carboxymethyl cellulose (CMC, cellulose-hydroxyacetic acid, [С6Н7О2(ОН)3-x(ОСН2СООН)x]n, where х = 0,08-1,5) – a cellulose derivative with carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers .

Modified cold accumulator is shown in Pic.2


Estimated temperature diffusion pattern inside the container is shown on Pic.3.

Modeling results have shown that the required temperature can be maintained for no less than 21 hours with the outside temperature being 22° С. Considering daily temperature fluctuations, containers storage and other parameters, the temperature range could be maintained for approximately 23 hours.

Based on the calculations made, the container with selected cooling agent was produced and handed to the customer for a trial run.

The customer has carried out an inner validation of the proposed solution and theoretical estimations have generally proved to work in operation. The results of test measurements are shown in Pic. 4.


Stage 3. Container modification for performance optimization

The second stage allowed an increase of the time of autonomous temperature range maintenance by selecting a combination of a cooling agent and container’s geometry. The solution proposed was in fact viable and could be applied in operation as was shown during trial runs made by the customer. However, the solution needed further optimization to guarantee temperature range maintenance within 24 hours with outside temperature of 27° С.

Taking into account container designing and testing experience, the third stage involved construction changes (geometry change) to a computer model, and a series of calculations performed with different quantities of the cooling agent. The sample obtained has successfully passed all tests, exceeding customer’s performance requirements.

The customer was highly satisfied with the professional approach and methods used by the HILGROUP company while solving the problem. Computer modeling significantly decreased the cost of container designing process, and accuracy of a designed model allowed the detection of the cooling agent the possessed the required characteristics. The customer has launched mass production of the container designed and is using the discovered solution to transport pharmaceuticals when auto refrigerators are not available.

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