A CFD study of adapting on-off cooling cycles in apple cold stores for energy saving.

Cooling during long-term storage of apples is a costly endeavour where electricity costs contribute up to 60% of the total variable costs at the end of storage. Here, the effect of controlling on-off cooling cycles on temperature and quality change uniformity and energy consumption is investigated with transient CFD models. The quality change of apples during the storage season as a function of position in the room is calculated with a firmness model using the FRISBEE tool. The on-off cooling cycle is regulated based on three different cooling differentials (0.4, 0.5 and 0.7°C). Temperature fluctuations were large near the edges of the stack. A
larger cooling differential led to larger fluctuations in the middle of the stack compared to the smaller differentials. Although off-cooling cycles were longer with larger differential, overall this strategy consumed more energy. Differences in apple firmness changes between the three cooling differentials are found insignificant. The smaller cooling differential resulted in a better overall performance.