Evaluating different loading scenarios in a refrigerated container for space utilisation and cooling

The ineffective utilisation of a 40-ft refrigerated container has been identified as a critical problem in the South African fruit industry. The positive trend of increasing demand and supply of Mediterranean fruit supports the need to optimise the space utilisation of a refrigerated container. The aim of this study was to evaluate different loading scenarios of standard packing systems (STD A, STD B, STD C) for container utilisation and cooling performance. The performance of the three loading scenarios was evaluated using a multi-parameter approach in a fully loaded refrigerated container. STD A and B design use 87.7% of the refrigerated container floor area while loading 20 pallets, while STD C design enables loading of 21 pallets using 92.1% of the refrigerated container floor area. This study used numerical simulations to characterise the packaging system’s airflow distribution and cooling performance in a fully loaded refrigerated container. The different standard packaging designs show similar airflow distribution with varying indices of heterogeneity. In the STD A design, 9 out of the 20 loaded pallet stacks receive low air velocity, primarily due to the bypass of airflow at the freestream region between the pallet stack and door. There was up to a 95% decrease in the average velocity from the pallet stack near the refrigeration unit (P1) to the pallet stack near the door unit (P9, P11). About 50% of the loaded pallet stack in the standard B design receives low air velocities. For STD C design, there was up to 97% decrease in the average velocity from P1 to P11, and 11 out of 21 loaded pallets received low airflow velocities. The nonlinear decrease in airflow rate in the standard packaging systems will lead to the development of warm spots in areas of low ventilation and thus accelerate the deterioration of fruit quality.