几何布置对CaCl_(2)溶液中草莓流态化速冻过程的影响

Effect of geometric arrangement on hydrofluidization quick-freezing process of strawberry in CaCl_(2) solution

冷冻液流态化速冻(hydrofluidization quick-freezing,HF)是一种新颖且前景广阔的食品速冻技术,由于传热系数极高因而加工时间短,大大提升了产品质量。借鉴常规流态化速冻原理,设计了一种HF室。利用Fluent对单个草莓在HF室内与质量分数为30%的低温CaCl_(2)溶液的传热传质进行分析,建立了合适的数值模型来描述速冻过程中CaCl_(2)溶液与草莓的传热与溶质扩散,并通过实验验证数值计算模型的准确性。研究了草莓距孔板高度H与孔板孔口直径d的比值对HF室内的流动过程、草莓冻结速率、溶质吸收等参数的影响。结果表明,H/d越大,草莓降温速率越低;当H/d小于8.88和大于26.66时,几何参数的改变对传热效果没有显著影响;草莓中溶质的吸收主要取决于降温速率,与H/d的关联不大。因此,合理设计HF室的几何布置能够最大限度地提升速冻效果,以获得更高品质的速冻产品。

Hydrofluidization quick-freezing(HF)is a novel and promising food quick-freezing technology.Due to the high heat transfer coefficient,the processing time is short and the product quality is greatly improved.Based on the principle of conventional fluidized quick freezing,an HF chamber was designed.Using Fluent to analyze the heat and mass transfer of a single strawberry in the HF chamber and the 30%low-temperature CaCl_(2) solution,a suitable numerical model was established to describe the heat transfer and solute diffusion between the CaCl_(2) solution and the strawberry during the quick-freezing process and the accuracy of the numeric calculation model was verified by experiments.The effects of the ratio of strawberry height(H)from the orifice plate to orifice diameter(d)on the flow process in the HF chamber,strawberry freezing rate,solute absorption,and other parameters were studied.Results showed that the larger the H/d,the lower the cooling rate of the strawberry.When H/d was less than 8.88 and greater than 26.66,the change of geometric parameters had no significant effect on the heat transfer effect.The absorption of solute in strawberries mainly depended on the cooling rate,and H/d had little correlation.Therefore,rationally designing the geometric layout of the HF chamber can maximize the quick-freezing effect and obtain higher-quality quick-frozen products.