不同包装结构对蓝莓压差预冷效果的影响

Influence of different packaging structures on forced air pre-cooling effect of blueberry

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。

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.