通风包装的开孔设计是影响果蔬采后品质的重要因素之一。以开孔均匀性为研究对象,利用计算流体力学(computational fluid dynamics, CFD)建立了2种内含3层果品的三维差压预冷模型,分别是新型均匀开孔(uniform vents, UV)模型与非均匀开孔(non-uniform vents, NV)模型。保持初始与边界条件一致,从箱内气流场、果品温度分布、冷却时间、速率以及均匀度等方面对比2种模型。结果表明:首先2种模型中的番茄冷却温度均沿冷气流方向由低到高呈梯度分布;其次受重力因素影响,UV内每层间番茄冷却温度存在较明显温差,NV在预冷前期表现出较好的效果而在后期收效甚微,即NV的1/2预冷时间较UV缩短了10.41%,但NV的7/8预冷时间却比UV增加了6.01%;最后,预冷结束后UV的均匀性比NV提高了14.1%。综合比较,在预冷环节中UV模型优于NV,研究为冷链通风包装的评估与设计提供了理论参考。
The hole design of ventilation packaging is one of the important factors for the postharvest quality of fruits and vegetables. This work took the hole uniformity as the research object and established two three-dimensional forced-air-cooling (FAC) models using computational fluid dynamics (CFD). The two models were named as uniform vents (UV) model and non-uniform vents (NV) model. By comparing with the temperature and velocity field distribution, cooling time, cooling rate, and cooling uniform of two packages under the same initial and boundary conditions, the following conclusions were drawn. Firstly, the cooling temperature of tomatoes in two models presented a gradient distribution from low to high along the direction of cold airflow. Secondly, due to the influence of gravity, there was a significant difference in cooling temperature between tomatoes in each layer of the UV model. Moreover, NV showed a good effect in the early stage of precooling, but little effect in the later stage. In addition, the half cooling time of NV was 10.41% shorter than that of UV, but the seven-eight cooling time of NV was 6.01% longer than that of UV. Finally, the uniformity of UV after precooling was 14.1% higher than that of NV. It showed that the UV package was superior to NV in the precooling process. This study provides a theoretical reference for the evaluation and design of cold chain ventilation packaging.
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