Characterising airflow and heat transfer within a multi-package of horticultural produce using a validated CFD model

• A validated CFD model analysed heat transfer and airflow within a tray filled with airtight clamshells. • Uneven airflow in trays caused cooling heterogeneity, with edge regions poorly ventilated. • Clamshell sealing edges act as barriers, limiting vertical diffusion of airflow. • Additional vent holes to the tray, when optimized, improved cooling uniformity and reduced pressure loss. Modified Atmosphere Packaging (MAP) is extensively used for highly perishable items to extend their shelf life by reducing their physiological activity. However, this solution involves non-ventilated packaging materials which hinder direct contact of cooling air with the product, thereby affecting the cooling rate of MAPs when packaged in ventilated trays. This research developed a Computational Fluid Dynamics (CFD) model to predict airflow within a half layer of a strawberry-ventilated pallet, consisting of two trays with 16 airtight clamshells (AC) each, representing modified atmosphere packaging. Within the ACs, the internal domain was modelled as an equivalent solid block representing both air and strawberries. Three tray designs were compared to assess the impact of vent holes and their positions on airflow behaviour and cooling rate. The model was validated using experimental data, showing a good agreement for air velocities and cooling characteristics. The analysis revealed that in the current tray design (TD 1) with a single main trapezoidal orifice on the longitudinal surface, airflow was uneven, with 24% traversing the headspace and 76% through the channels between ACs. This design caused recirculation near the tray's edge and poor ventilation within the channels of this area, leading to heterogenous cooling among ACs. This heterogeneity in cooling resulted in differences of up to 2 h in Half Cooling Time. Numerical simulations indicated that adding ventholes to the tray does not guarantee an improved cooling rate and uniformity. The effectiveness of vent holes depended on their placement relative to ACs arrangement.