冷库内空气参数对食品冻结的影响研究

The Influence of Air Parameters in Cold Storage on Food Freezing

冷库中空气参数分布的不均匀会导致不同位置食品的冻结过程差异,本文提出了一个模拟冷库在完整食品冻结周期内各参数变化的动态模型,基于各子系统间的传热传质平衡而建立。对分散在库房空间中的冻结食品,利用CFD模拟得到其冻结条件的数值分布,根据其冻结条件对该库房内的食品冻结过程进行分段集中模拟。结果表明,在冻结过程初期,食品的负荷是主要负荷,随着冻结过程的进行,食品负荷逐渐减小,而风机等其他负荷所占比重逐渐增大。库房内空气参数分布存在局部差异,风速分布比温度分布差异性更大,导致食品冻结过程存在差异,最快和最慢完成冻结的时间相差11.5 h。在冻结前期,库房温度波动对食品降温过程影响不大,而在冻结后期库房温度波动会使食品温度产生波动,影响食品冻结质量。

The inhomogeneous distribution of air parameters in cold storage leads to local differences of food freezing at different loca-tions. A dynamic simulation on parameter changes during a complete freezing process in cold storage was presented based on the heat and mass balance between subsystems. CFD method was employed to calculate the distribution of freezing condition for foods distributed in storage room. Then all foods were separated into several groups and modeled based on the freezing condition. Results show that during the initial stage of freezing process, heat release of food is the main source of cooling load, which decreases as the freezing process goes on. The importance of other loads increases gradually. Because of the inhomogeneous distribution of air parameters in cold storage, the freez-ing process and freezing time varies from each other and shows a time difference as big as 11. 5 hours between the fastest and slowest freez-ing processes. The fluctuation of air temperature in storage room has no effects on food freezing at earlier stage, which causes some fluctu-ations of food temperature at later stage of freezing process.