Fruit cooling performance analysis within a fully loaded refrigerated container: CFD modelling and validation

Refrigerated containers (RCs) are crucial for transporting fresh produce to international markets, significantly influencing fruit quality along the cold chain. Although RCs are a mature technology, fresh produce industries report challenges relating to temperature heterogeneity and ineffective monitoring approaches. This study developed and validated a computational fluid dynamics model to characterise airflow and heat transfer inside an RC packed with standard ventilated packaging for South African citrus fruit. The model was implemented with an accurate representation of a refrigeration unit, incorporating the presence of fans and evaporator coils based on experimental characterisations. Air speed and cooling validations showed good agreement with the models. Simulations identified a vertically dominant airflow pattern, with air speeds within the pallets ranging from 0.03 m s^-1 to 0.16 m s^-1. Air velocities within the pallet regions were categorised into four zones: a turbulent air recirculation zone, a high-velocity stabilisation zone, a declining air velocity zone, and a heterogeneous air velocity zone near the door. Excessively cooled regions were identified, potentially increasing chilling injury risk, a primary concern for South African citrus exports. The study evaluated temperature monitoring, and an optimal position for hygrothermal sensors was proposed for single-device monitoring. It was further shown that air temperature data is conditionally representative of pulp temperature. The insights gained can guide industry practitioners in enhancing temperature monitoring practices and inform future research on optimising RC cooling efficiency and minimising chilling injury risks to improve fruit quality and reduce waste in the fresh produce supply chain.