CFD-based analysis of the cooling capacity of a refrigerated container as a function of produce loading temperature

The global fresh fruit market relies heavily on temperature control during long-distance transportation of produce across the globe. Refrigerated containers (reefers) keep temperature-sensitive cargo at their required temperature throughout the supply chain, playing a vital role as the carrier of the global produce trade. Significant increases in reefer freight rates have placed substantial pressure on the fruit export industry to find efficient use of reefers. This paper investigates the capacity and limitations of reefers for apple fruits. A realistic computational fluid dynamics (CFD) model of airflow and heat transfers inside a fully loaded commercial reefer was developed. The cooling dynamics of the refrigeration unit were incorporated into the model realistically. The model also incorporated the ambient conditions and the respiration heat generation of the produce. Fruit quality attributes were also measured before loading and after unloading at the end of the experiment. Temperature data obtained from a full-scale reefer experiment with apple fruit were used for model validation. The airflow distribution showed significant spatial variation. Pallets close to the cooling unit side had higher airflows, while pallets at the door side had lower airflows. The middle air gap between pallet rows is characterised by high airflows, leading to an undesirable short-circuiting airflow. The steady-state simulation was used as an initial condition for the transient simulation. The result of the transient simulation showed the highest and lowest ambient temperatures at the door and cooling unit sides, respectively. The container was able to bring down the fruit core and pallet ambient temperatures to an average of <1.8°C (numerical) in less than 2 days of cooling for both rows. The fruit quality analysis showed acceptable quality attributes at the end of the experiment.