真空槽内不同装载率对真空预冷效果的影响

当真空预冷设备结构一定时，预冷工艺过程主要由预冷果蔬品种及装载率决定。通过分析预冷过程中槽内压力的动态变化过程，讨论了质交换系数及装载率对槽内压力的影响．在此基础上，进行了多棵白菜、单棵白菜、生菜及蘑菇的真空预冷试验，装载率分别为53．6％、3.76％、11．2％和20．5％．试验结果表明，装载率较大时，槽内压力能保持在一个较高的值，从而防止预冷果蔬表面结冰现象；对于质传递系数较大的果蔬，装载率可以低一些，从而缩小预冷时间。因此在进行真空预冷时要根据果蔬种类确定装载率。

Effect of Packed Rate in Vacuum Tank on Vacuum Pre-Cooling

The process of vacuum pre-cooling is determined by the type of vegetable or fruit and the packed rate when the vacuum pre-cooling apparatus is provided. By analyzing the dynamic change of pressure in the vacuum tank during the pre-cooling, the effects of the mass exchange coefficient and the packed rate on the pressure in the tank were discussed. And the vacuum pre-cooling experiments of Chinese cabbage, lettuce and mushroom were carded out, with packed rates of 53.6%, 3.76%, 11.2%, and 20.5%, respectively. The results show that when the packed rate is high, the pressure in the tank is great and the frozen phenomenon can be prevented. As for the vegetable or the fruit with a greater mass exchange coefficient, the packed rate can be lower for shortening the pre-cooling time. So in the process of vacuum pre-cooling, the packed rate should be decided by the type of fruits and vegetables.