中强脉冲电场叉指式平板处理室的多物理场仿真与试验

Multi-physical field simulation and experiments of parallel treatment chamber with interdigital structure under moderate intensity pulsed electric fields

关键词:  平板式处理室  杀菌  叉指结构  中强脉冲电场  COMSOL Multiphysics

Key words:  parallel treatment chamber  sterilization  interdigital structure  moderate intensity pulsed electric field  COMSOL Multiphysics

摘要:

处理室是脉冲电场系统的关键部件，为改善处理室的结构和性能，设计并优化一种在中强脉冲电场下的处理室。运用COMSOL Multiphysics软件对优化前后处理室的电场、流场和温度场进行分析，测定物料出口温度和杀菌效果对优化效果进行实际评价，基于优化后的处理室对比中强脉冲电场处理和巴氏杀菌处理对蓝莓果汁的品质影响。结果表明:1)研究得到的直角型叉指式平板处理室，除电极拐角处存在电场尖峰外，其他区域的电场强度分布均匀，均为2 kV/cm，与理论值相同，优化后的圆角型叉指式平板处理室在拐角处消除了电场尖峰，电场强度峰值由22.7 kV/cm降低至2.64 kV/cm，电场强度分布更加均匀，物料出口温度降低了4.3 ℃，温度和流速分布均得到改善；2)基于叉指式平板处理室搭建的中强脉冲电场处理系统具有显著的杀菌效果，电场强度大于2 kV/cm时，直角型和圆角型叉指式平板处理室均使大肠杆菌菌落数下降了3 lg(CFU/mL)以上，但圆角型叉指式平板处理室的物料温度升高幅度显著降低，效果更好，与仿真结果一致；3)与热处理相比，中强脉冲电场处理更好地保持了蓝莓果汁的pH、颜色、花色苷和抗氧化能力。本研究研发的叉指式平板处理室具有良好的杀菌效果，优化后物料温升更小，能够较好地保持蓝莓果汁的品质。

Abstract:

Treatment chamber is the key equipment of the pulsed electric field system. To develop the structure and performance of the treatment chamber, a type of treatment chamber under moderate intensity pulsed electric fields(MIPEF)was designed and optimized. COMSOL Multiphysics software was used to analyze the electric field, flow field, and temperature field of the treatment chamber before and after optimization. The practical effects were evaluated by measuring material outlet temperature and sterilization effect. Based on the optimized treatment chamber, the effects between MIPEF treatment and pasteurization treatment on the quality of blueberry juice were compared. The results showed that in the right-angled type of interdigital parallel treatment chamber obtained by this study, except for the sharp electric fields at the corners of the electrodes, the electric intensity distribution was uniform in other areas with the theoretical value of 2 kV/cm. The corner-filleted type of interdigital parallel chamber after optimized showed a more uniform electric intensity distribution that the peak electric intensity was declined from 22. 7 kV/cm to 2. 64 kV/cm with the sharp electric fields eliminated around the corners, and the material temperature at the exit was reduced by 4. 3 ℃ with the temperature and velocity distributions improved. Significant sterilization effects were obtained by the MIPEF processing systems built with the interdigital parallel treatment chambers, and more than 3 lg(CFU/mL)reduction of E. coli was observed when the electric intensity was more than 2 kV/cm both in the right-angled and the corner-filleted type of interdigital parallel treatment chambers. However, a better effect was observed that a smaller increment of material temperature was acquired in the corner-filleted type of interdigital parallel chamber, which was consistent with the simulation results. Compared to heat treatment, MIPEF treatment better kept the pH, color, anthocyanin, and antioxidant capability of blueberry juice. Therefore, the interdigital parallel treatment chambers display a good performance on sterilization, and it has a lower temperature rise and efficient preservation of the quality of fresh blueberry juice after optimization.