干冰喷射进出口位置对草莓速冻过程的影响

Influence of inlet and outlet position of dry ice spray on strawberry quick-freezing process

该文围绕干冰喷射掠过草莓,使草莓快速降温冻结的特性,提出了多种不同干冰入口和出口位置的草莓速冻间模型,分析干冰不同进出口位置的草莓速冻间模型对草莓的中心温度、表面温度、速度场的影响。结果表明,在入口半径25 mm,出口半径50 mm,搁板厚度5 mm,所有草莓表面温度降到-35℃及以下,草莓中心温度降到-18℃及以下时,模型a所有草莓的中心温度最高和最低相差仅为6.2℃。模型c所有草莓的中心温度最高和最低相差较小为9.9℃,模型c草莓表面温度均匀,速冻时间最少,干冰流线分布规则,可以实现流速和传热的最佳耦合,高效速冻草莓,满足草莓速冻生产的需求。对优化的结果(模型c和模型f)进行实验验证,草莓表面温度和中心温度达到标准时,误差分别为2.10%、5.79%和3.93%、5.71%。草莓干冰速冻前后的品质指标均优于草莓速冻标准。

This paper focuses on the characteristics of dry ice spraying over strawberries to make them cool down and freeze quickly.Several models of strawberry quick-freezing room with different positions of dry ice inlet and outlet were presented.The effects of strawberry quick-freezing room models with different dry ice entry and exit positions on center temperature and surface temperature of strawberry,velocity field were analyzed.The results showed that,when the inlet radius was 25 mm,the outlet radius was 50 mm,the shelf thickness was 5 mm,the surface temperature of all strawberries dropped to-35℃or below and the center temperature of strawberries dropped to-18℃or below.The inlet was on the same side and arranged symmetrically,and the difference between the highest and lowest center temperatures of all strawberries was only 6.2℃(model a).Besides,the difference between the highest and lowest center temperature of all strawberries was 9.9℃(model c).Furthermore,the best coupling of flow velocity and heat transfer of the model c could be achieved by uniform surface temperature,minimum quick-freezing time and regular distribution of dry ice streamline.It could freeze strawberries efficiently and meet the demand of strawberry quick-frozen production.The results were verified and the errors between experiment and simulation were 2.10%and 5.79%(model c)3.93%and 5.71%(model f)respectively when the surface temperature and the center temperature reached the standard of quick-frozen strawberry.The physical and chemical properties of strawberries before and after quick-freezing with dry ice were better than the standard of quick-frozen strawberries.The results obtained lay a foundation for the further development of energy-saving and environment-friendly dry strawberry devices.