果汁等温结晶过程冰晶生长的相场法模拟

Phase-field modeling of isothermal crystallization process in juice crystal growth

针对冷冻浓缩过程冰晶夹带造成果汁可溶性固形物损失而限制其推广使用的问题,采用国内外描述相变微观结构的相场模型,将果汁体系视为水和溶质二元系统,从微观上模拟冰晶生长的演变过程。探讨扰动对晶体二次分枝生长的影响,修正各向异性的模数,并通过改变各向异性强度系数,获得冰晶模拟的各向异性强度系数合适取值,进一步分析结晶模拟时间对模拟结果的影响,与试验结果进行验证。结果表明:扰动通过诱发侧向分枝的生长,从而影响晶体形貌;各向异性会影响冰晶生长形貌,各向异性强度系数太小,分枝不明显,太大,会造成冰晶非对称生长;模拟结果与试验结果两者吻合较好。

In order to simulate the evolution of ice crystal growth from the microscopic, regarding juice as water and solute in binary system, the phase-field model theory which had been widely used in the Phase transition of the microscopic structure at home and abroad was used to stimulate the ice growth. The influence of disturbance on crystal growth of lateral branch was discussed. By modifying anisotropic modulus and changing the anisotropic strength parameters,the suitable scope of the anisotropic strength parameters were to obtain to further study the effect of different crystallized time on the evolution of ice crystal growth. Results showed that the disturbance would influence the results of the growth of lateral branch, the growth of lateral branch wouldn＇t appear without disturbance; when the crystal anisotropic modulus valued 6, a hexagonal crystal structure could be simulated; the value of the Anisotropic strength parameter range was about 0.02 to get right simulation results of ice crystal growth evolution,too small or too big value would get unsatisfactory growth results. It validated the simulation results coincided well with experiment.