Analyzing and optimizing refrigerated hypobaric storage chambers for lime fruit via multiphysics modeling

Storing fresh produce refrigerated under controlled atmosphere in which the oxygen concentration is reduced, can drastically extend the storability of the product. Within low pressure or hypobaric storage, a controlled atmosphere is created by lowering the total pressure of the air. Previous research on lab-scale has demonstrated significant advantages of hypobaric storage on the quality maintenance of several products. Currently, storage chambers of 750 L are being optimized to apply the technique commercially in a convenient way. However, maintaining uniform temperatures within closed, airtight storage chambers is rather challenging, and quality issues have been encountered during storage because of local hotspots or humidity problems. In this research, the storage of lime fruit inside hypobaric chambers was studied numerically using physics-based modeling. The study sought to 1) understand and analyze the cooling of fruit by mapping the developed temperature gradients inside the chamber, and 2) optimize the design and operation of the chamber to ensure more uniform thermal conditions. At reference storage conditions (30 kPa and 10 °C), temperatures up to 12.5 °C developed inside the chamber. The cooling inside the chamber mainly occurred via conduction. By lowering the storage temperature or operating pressure, the temperature gradients were strongly reduced. To further reduce the temperature heterogeneity within the chamber, additional aluminum plates (“fins”) were introduced within the chamber. Such cooling fins were shown to be effective in lowering the temperature gradients by 70 %. The insights obtained in this study can also be used to optimize the storage of other crops.