Mathematical modelling of cooling efficiency of ventilated packaging: Integral performance evaluation

Abstract

The current packaging designs and the efficiency of forced-air cooling (FAC) of fresh produce can be considerably improved by comprehensively comparing and evaluating the existing packaging designs. This study presents a market survey that studies samples of typical apple cartons used in China. Furthermore, by combining experiment and computational fluid dynamics (CFD) modelling, a novel integral approach is proposed to evaluate cooling rate and uniformity, energy efficiency, and fruit quality (including safety) as a result of FAC for different ventilated-packaging designs. The process uses CFD to simulate the three-dimensional spatio-temporal distributions of airflow and product temperatures during precooling. In addition, experiments on chilling injury and mass loss are also reported. The results show that the optimum fresh-fruit packaging design depends on the product size and the location of the product and tray inside the packaging. For all existing package designs, the optimal air-inflow velocity is found to lie in the range 0.4–1m/s (or 3–5Ls−1kg−1), any further increase in airflow rate simply wastes energy because it leads to a relatively low increase in cooling rate and uniformity. The level of chilling injury and mass loss per box show a different trend with increasing air-inflow velocity. The accuracy of the CFD simulations was confirmed by a good agreement with experiments. The maximum root-mean-square error and mean absolute percentage error for produce temperature are 0.727°C and 18.69%, respectively. This research unveils the advantages and disadvantages of the various existing packaging designs and provides a reliable theoretical and experimental basis for achieving an integral evaluation of the performance of FAC.