过冷度影响冰晶生长的相场法研究

Study on under-cooling influence on ice crystal growth using phase-field method

采用Wheeler模型对果蔬速冻保鲜工艺中的冰晶生长过程进行模拟,研究了过冷度对冰晶生长行为的影响。结果表明:模拟结果和试验结果呈现的冰晶组织特征一致,冰晶形态具有典型的六重对称性。当过冷度小于0. 45时,随着过冷度的增加,冰晶尖端生长稳态速率以二次函数形式增加,尖端曲率半径减小,冰晶生长由扩散控制;当过冷度大于0. 45时,冰晶尖端生长稳态速率以线性函数形式增加,尖端曲率半径增加,冰晶生长由动力学控制。因此,选择合适的过冷度,使冰晶尖端的曲率半径最小,从而避免大冰晶破坏细胞壁而导致解冻时汁液流失、褐变。

The Wheeler model was used to simulate ice crystal growth in fruit and vegetable quick - freezing and preserva- tion process, the effect of under - cooling on the behavior of ice crystal growth was studied. The results show that the simulation results and the experimental results are consistent with the characteristics of the ice crystal structure, and the morphology of ice crystal has a typical six - fold symmetry. When the degree of under - cooling is less than 0.45, as the degree of under -cooling increase, the steady - state tip velocities increases in a quadratic function, the tip radius of curvature decreases, and the growth of ice crystals is controlled by diffusion. When the degree of under - cooling is greater than 0.45, the steady - state tip velocities increase linearly, the tip radius of curvature increases, and ice crystal growth is controlled by dynamics. Therefore, the proper degree of under - cooling is selected so that the tip radius of curvature is minimized, so as to avoid the loss of juice and browning due to the destruction of the cell wall by the large ice crystals.