Implementation of next-generation packaging systems in high cube refrigerated containers for efficient cooling and improved volume usage

The introduction of a new packaging system (design) presents the industry with a unique opportunity to utilise the refrigeration system of containers more effectively. This would enhance fruit quality preservation, reduce fuel consumption of the refrigeration unit (lower shipping costs) and enable the improved application of various temperature treatments (e.g. intermittent warming, ambient loading and cold treatments).

Before an optimal packaging system can be developed, it is necessary first to evaluate the design space (i.e. the refrigerated container). The study, therefore, developed a dynamic container CFD model, which was then validated using two container scenarios. The validated model was then used to explore both the current load-out and explorative scenarios.

The study successfully validated the container model. The primary contribution here was the development of a refrigeration unit model, which responds realistically (airflow and cooling) to whatever is loaded in the container. Simulations showed that the use of void plugs are highly beneficial to cooling performance. However, this benefit was marginal compared to the use of packaging systems that fully utilises the floor space. In this case, airflow bypass was eliminated, and the resulting air thus flowed uniformly through the packaged fruit. Detailed characterisations of the containers cooling performance were documented, which provide valuable insights into optimal packaging and ventilation designs.

For optimal cooling in a refrigerated container, pallets need to have an airflow resistance (vertical axis) lower than 2500 kg m^-4. Depending on the number of cartons in a stack (more cartons require more ventilation), this equates to about 5%, aligned, ventilated area. Additionally, ventilation resistance along the vertical axis needs to be equal to or less than that of ventilation along the horizontal axis. Finally, the use of packaging systems that fully utilise the container floor area, not only significantly improve packing density, but also drastically improve cooling performance. Practical implementation of these or similar novel pallet designs needs to be considered in light of cost/benefit analyses that consider the compatibility with current equipment and facilities

This study quantified the advantages of adopting a more optimal packaging system approach. These recommendations now need to be evaluated by industry and weighed against the practical costs and benefits of implementation.