Efficiencies Of Natural Convection In Passive Pallet Shippers
Bulk transportation of temperature sensitive pharmaceuticals and biologics has become a common practice due to complex global supply chains. This imperative has prompted pharmaceutical companies to look at more efficient and economical means of temperature controlled distribution. Passive packaging systems are one of the proven and repeatable methods for international bulk shipments of temperature sensitive products.
Currently, many bulk shipments of pharmaceutical and biological products utilize passive pallet shippers consisting of six panels assembled to form a container. Given the large size of a bulk shipping container a significant amount of product surface area is exposed to ambient conditions. Therefore, a considerable mass of refrigerants is required to maintain product temperatures within the specified criteria. Placement and quantity of refrigerants is critical to maintain stable product temperatures. The conventional approach for refrigerant placement is to position refrigerant on all six sides of the product. This would ensure that all exposed product will be protected. This approach, however, has several disadvantages:
- Difficult and inefficient packout process. Refrigerants located around the vertical walls have a tendency to tip over while loading or require expensive brackets
- Lengthy packout process which can result in out of specification refrigerant and product temperatures prior to sealing the package and excessive labor costs
- Significant refrigerant mass is required to maintain stable product temperatures resulting in high freight fees
Given the aforementioned disadvantages, an innovative approach to pallet shipper thermal design is presented. This approach utilizes convection (the flow of cool air) to provide sufficient product protection and maintain the required product criteria. This approach allows for the elimination of refrigerants located around the vertical walls of the pallet shipper and thereby greatly simplifying the packout process while minimizing costs. The packout procedure becomes less time consuming, more efficient, and drastically reduces the overall container weight.