送风风速对苹果差压预冷性能的影响
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“十二五”国家科技支撑计划资助项目 (2013BAD19B04) 和欧盟FP7资助项目(PIRSES-GA-2013-612659)


Effect of Air-inflow Velocity on Cooling Efficiency during Forced-air Precooling of Apples
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    摘要:

    收后果蔬的及时预冷已成为供应商一项必备的增值业务,提高其预冷均匀性及预冷速率不仅可以延长果蔬货架期、提高预冷吞吐量,整体冷链物流的经济效益也可得到直接保证与提升。以富士苹果2层瓦楞纸包装箱为研究对象,建立箱体、衬垫及果品的三维实体模型,将果品呼吸热、表面蒸发热、冷凝热及对流传热作为果品区域内部热源,利用CFD模拟预冷过程中不同送风速度下箱体内部温度分布情况,对比分析不同工况下的冷却时间、瞬时冷却速率以及瞬时冷却均匀性,从冷却时间与冷却所需能耗考虑给出较佳的预冷送风速度。研究结果表明,当送风速度超过2.5m/s时,其制冷时间、冷却速率及冷却均匀性无显著改善,通过将果品F6、S6表层、中心温度模拟值与实验值对比验证得出,温度最高偏差不大于1.5℃,其最大均方根误差与平均相对误差分别为1.179℃和13.6%。该研究为提高苹果通风包装箱内部预冷均匀性,选取较佳的送风速度,降低预冷时间及减少不必要的预冷能耗提供了理论参考。

    Abstract:

    To ensure the quality and safety, and extend storage and shelf life of horticultural products across the entire coldchain, a critical step in the postharvest cold chain is rapid precooling after harvest to remove field heat. This work established a threedimensional mathematical model of airinflow and heat transfer for analyzing the aerodynamic and thermal forcedconvection cooling of vented packages simultaneously. A direct model that uses the explicit geometry of stacked products in boxes was developed earlier and was used to study the local and average airinflow through stacks of horticultural products (the package wall, trays and apples). This study is based on an existing twolayer corrugated box for precooling fresh apples. We accounted for the heat of respiration, transpiration, condensation and convective heat flow inside the produce zone. The results show that a reasonable increasing cooling rate and uniformity are obtained with an increase in airinflow velocity to 2.5m/s; any further increase in airinflow velocity simply wastes energy because it leads to a relatively low increase in cooling rate and uniformity. The model was verified by comparing its results to those of experiments. The predicted results were consistent with the measured results. The maximum temperature deviation was less than 1.5℃, and the maximum root mean square error and average relative error for produce temperature were 1.179℃ and 13.6%, respectively. This research thus provides a reliable theoretical basis for improving air-inflow and produce-temperature uniformity and minimizing energy consumption during forcedconvection cooling of produce.

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韩佳伟,赵春江,杨信廷,钱建平,邢 斌,范蓓蕾.送风风速对苹果差压预冷性能的影响[J].农业机械学报,2015,46(11):280-289.

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  • 收稿日期:2015-07-09
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  • 在线发布日期: 2015-11-10
  • 出版日期: 2015-11-10