冻肉射频解冻过程中温度变化的模拟与测定

Simulation and Determination of Temperature Changes During Radio Frequency Thawing of Frozen Pork

摘要:

对冻肉射频解冻过程中的温度变化进行了理论模拟和实验测定。主要目的在于验证利用COMSOL Multiphysics软件来模拟冻肉射频解冻温度变化的可行性，以计算机模拟过程代替繁琐的实际测定过程，便捷地获得适宜的射频解冻条件。测定了猪肉在27 MHz频率下在-18 ℃~20 ℃范围内的介电性质，采用有限元分析方法建立了静电场-热传导双向耦合模型，研究了射频仪极板间距和肉块厚度对冻肉在射频解冻过程中温度变化的影响，并与实验测定结果进行了比较。结果表明，模型计算温度值与实验测定温度值有很好的一致性。解冻速度呈现先快（-18 ℃~-5 ℃）后慢（-5 ℃~ -1 ℃）再快（-1 ℃以上）的变化趋势。极板间距越大，肉块厚度越厚，则解冻所需时间越长。极板间距越大，肉块厚度越小，则射频解冻后肉块内温度分布越均匀。通过冻肉射频解冻过程中温度变化的模拟，建立了射频条件、物料性质与解冻效果之间的关系，使软件模拟预测解冻过程成为可能，为射频解冻技术的推广应用提供了便捷的途径。

Abstract:

Temperature changes during radio frequency thawing （RFT） of frozen pork were investigated using theoretical simulation and experimental determination. The feasibility of simulating temperature changes during RFT of frozen pork using the software COMSOL Multiphysics has been confirmed，which suggests the optimization of RFT conditions could be easily determined by software instead of time-consuming and laborious experiments. Dielectric properties of pork at 27 MHz were estimated within -18 to 20 ℃. A coupled electro-quasistatic-thermal model was established using finite element method to simulate the RFT process. The effects of temperature changes during RFT of frozen pork were studied，such as the electrodes distance and meat thickness. The simulation results showed a good consistency with the experimental determinations. Thawing rate changed from fast （-18 ℃~-5 ℃） to slow （-5 ℃~-1 ℃），and turned back to fast （>-1 ℃）. A longer thawing duration was required if the electrodes distance and meat thickness were increased，while a better temperature distribution could be received if the electrodes distance was increased but the meat thickness was decreased. The relationship of radio frequency conditions，material properties and thawing effects has been established via the simulation of temperature changes during RFT of frozen pork. The confirmation of predicting thawing process by software simulation provides a wide range of application perspective for RFT.