The impact of food type, wall-loading of pallets, and chute length on cargo temperature heterogeneity of refrigerated trailers

Refrigerated transport of food products in trailers is a crucial part of the cold chain. The main challenge is to keep the products within the desired temperature range to maintain their salability and ensure food safety. Pallets are typically positioned against the wall, affecting airflow and cooling efficiency, leading to suboptimal storage temperatures. We use physics-based simulations and computational fluid dynamics to explore how non-wall-loading, semi-wall-loading, and wall-loading affect the temperature distribution within the cargo. We examine three cases: packaged lettuce, cooled chocolate, and frozen meat, and the effects of a full, half-length, and no chute. Results indicate that alternating pallet arrangements significantly improve airflow uniformity and cooling performance, reducing average temperatures after 72 h by over 0.8 °C for lettuce and 0.2 °C for chocolate compared to non-wall and wall-loading configurations. Lettuce is least affected by wall loading, while chocolate shows localized warm areas with 15 °C near the wall when supply air is at 14 °C, due to low thermal conductivity. Frozen meat is most susceptible to warming, with near-wall temperatures exceeding −18 °C, influenced by low pallet height, low thermal diffusivity, and a by factor two higher external-internal temperature gradient than the other cases. A shortened chute increases temperature heterogeneity and raises mean trailer door-end pallet row temperature by up to 3 °C. Despite better cooling with alternating pallet arrangements, wall contact should be minimized to avoid local warmer spots. Our results advocate avoiding wall loading to enhance temperature uniformity and cold chain effectiveness.