Abstract: Rapidly removing field heat after harvest is a key step in food cold chain logistics to ensure the good quality of fruits and vegetables and consequently extend their storage and shelf life. The internal structure of package filled with trays and products is complex, resulting in serious cooling heterogeneity. The present study focuses on the effect of tray design on the precooling process of apples and attempts to give the optimal gap width between tray and box wall. The widely-used corrugated double-layered apple packaging box in the market was chosen as the research object, a three-dimensional model was established, and the precooling process of apples was studied by using the direct computational fluid dynamics (CFD) simulation method. Results indicate that increasing the gap width is an effective way to shorten the precooling time and improve the precooling uniformity. However, the gap width can not be increased infinitely. Therefore, considering the influence of the gap width increment on both the precooling time and the uniformity of apple temperature, the optimal gap width increment between the tray and the box wall should be 7.5 mm. This results in shorter precooling time and better precooling uniformity.

Key words: forced-air precooling, direct computational fluid dynamics(CFD) simulation, tray design, precooling time, precooling uniformity