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浙江大学学报（农业与生命科学版）
Journal of Zhejiang University (Agriculture and Life Sciences)  2020, Vol. 46 Issue (1): 47-54    DOI: 10.3785/j.issn.1008-9209.2019.08.121
Research articles     
Influence of different packaging structures on forced air pre-cooling effect of blueberry
Da WANG1,2(),Xiangzheng YANG1(),Binguang JIA1,Maoyu WU1
1.Jinan Fruits Research Institute, All China Federation of Supply and Marketing Cooperatives, Jinan 250200, China
2.School of Energy and Power Engineering, Shandong University, Jinan 250061, China
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Abstract  

In order to overcome the disadvantages of the large pressure loss, temperature unevenness and slow cooling rate, a packaging system which was suitable for the small diameter fruit of pre-cooling was discussed by using computational fluid dynamics (CFD) software. The mathematical models of four types of packaging systems were established, taking the current harvesting, pre-cooling and storage boxes of blueberry as the research objects to investigate the influence of height of trapezoidal hole on the pre-cooling effect of blueberry when the opening rate was constant. The results indicated that the change trend of pre-cooling time of the four types of packaging systems was box 1 ＞ box 2 ＞ box 4 ＞ box 3, and the pre-cooling time and the height of the trapezoidal hole showed the positive correlation; the change trend of pressure loss, unevenness and plot ratio were the same, all of which were box 4 ＞ box 3 ＞ box 2 ＞ box 1, and there was negative correlation between the pressure loss, unevenness, plot ratio and the height of the trapezoidal hole. The change rate of pre-cooling time, pressure loss, unevenness and plot ratio were 6.98%, 24.10%, 28.10% and 23.30%, respectively, when the trapezoidal height increased from 20 mm to 34 mm. In general, pre-cooling time, pressure loss, unevenness and plot ratio should be comprehensive considered when the packaging systems of blueberry are chosen. Box 3 or 4 should be opted, if highly cooling rate and plot ratio are carried out. Contrarily，box 1 or 2 are a better choice，if the operators want to decrease energy consumption and increase uniformity of blueberry on pre-cooling.

Key words： forced air pre-cooling      blueberry      pre-cooling packaging system      unevenness      pressure loss     
Received: 12 August 2019      Published: 25 February 2020
CLC:  TS 255.36  
Corresponding Authors: Xiangzheng YANG     E-mail: wangda19910@163.com;yangxiangzheng318@163.com
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Da WANG
Xiangzheng YANG
Binguang JIA
Maoyu WU
Cite this article:

Da WANG,Xiangzheng YANG,Binguang JIA,Maoyu WU. Influence of different packaging structures on forced air pre-cooling effect of blueberry. Journal of Zhejiang University (Agriculture and Life Sciences), 2020, 46(1): 47-54.

URL:

http://www.zjujournals.com/agr/10.3785/j.issn.1008-9209.2019.08.121     OR     http://www.zjujournals.com/agr/Y2020/V46/I1/47


不同包装结构对蓝莓压差预冷效果的影响

针对现有小果径果蔬预冷包装压力损失大、温度不均匀、降温速度慢等问题，利用计算流体力学（computational fluid dynamics, CFD）软件，以目前通用的蓝莓采摘、预冷、贮藏包装箱为研究对象，建立4种箱体结构的数学模型，探究在相同开孔率下，梯形孔高度对蓝莓预冷效果的影响。结果表明：总开孔率一定时，梯形高度与预冷时间呈正相关关系，4种箱体预冷时间变化趋势为箱体1＞箱体2＞箱体4＞箱体3；4个箱体的压力损失、预冷不均匀度与容积率的变化趋势一致，均为箱体4＞箱体3>箱体2＞箱体1，即压力损失、不均匀度、容积率与梯形高度呈负相关关系。梯形高度从20 mm增加到34 mm时，预冷时间、压力损失、不均匀度和容积率变化率分别为6.98%、24.10%、28.10%与23.30%。总之，蓝莓预冷箱体的选择需要综合考虑预冷时间、压力损失、均匀度与容积率因素，若是想实现快速预冷和预冷过程中的高容积率，则选择箱体3或者箱体4；若是想减少压差风机的能耗，提高预冷均匀性，则选择箱体1或者箱体2。


关键词： 压差预冷,  蓝莓,  预冷箱体,  不均匀度,  压力损失 
Fig. 1 Structure of pre-cooling packaging system for blueberry
Fig. 2 Four openings of packaging boxesA. Box 1； B. Box 2； C. Box 3； D. Box 4.

名称

Name

密度Density/(kg/m3)比热容Specific heat capacity/(J/(kg?K))导热系数Thermal conductivity/(W/(m?K))
蓝莓 Blueberry1 061.9cp=5.40×10－3t2-1.51t +3 183.39λ=-5.12×10－7t2+4.33×10－4t2-0.12t +11.50

PVC 包装箱

PVC packaging box

1 0501 3400.12
空气Air1.2251 006.40.024 2
Table 1 Summary of physical parameters
Fig. 3 Arrangement of temperature measurement points
Fig. 4 Blueberry pre-cooling experimentA. Testing box of forced air pre-cooling； B. Pre-cooling packaging system for blueberry.
Fig. 5 Comparison of average temperatures for experiment and simulation
Fig. 6 Pre-cooling time of the four types of packaging systems
Fig. 7 Cooling proportionality coefficient of the four types of packaging systems under different air velocitiesA. Air velocity is 1 m/s; B. Air velocity is 2 m/s; C. Air velocity is 3 m/s.
Fig. 8 Variation of pre-cooling unevenness over time under 2 m/s
Fig. 9 Variation of pre-cooling unevenness with average temperature of blueberry under 2 m/s
Fig. 10 Velocity field in the packaging systems under 2 m/sA. Box 1； B. Box 2； C. Box 3； D. Box 4.
Fig. 11 Pressure loss of the four types of packaging systems
Fig. 12 Plot ratio of the four types of packaging systems
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