不同送风和载物方式作用下冲击式速冻设备中虾仁冻结过程的比较

Comparison of freezing processes of shrimp in impingement quick-freezing equipment in different air supply and load modes

摘要:

以明虾虾仁为研究对象，利用数值模拟结合实验验证的方法，研究两种送风方式（单侧送风和双侧送风）和两种载物方式（板带载物和网带载物）对虾仁冻结过程的影响，找到使虾仁冻结时间最短的送风和载物方式。研究发现：对于虾仁冻结来说，采用双侧送风+网带载物可以使虾仁表面流场流速更大，有利于提高换热效率，减少虾仁冻结时间，相对于其他送风方式和载物方式来说可缩短虾仁冻结时间的14%~25%；双侧送风有助于低速侧形成提高虾仁下表面流速的涡流，而网带载物可以避免在虾仁下侧面与网带交界处以及虾仁头部形成射流“真空区”，上述均有助于提高虾仁表面风速，缩短虾仁冻结时长；但是冻结速度越快，虾仁冻结均匀性则越差。在本次实验中，虾仁内外最大温差出现在实验组D（双侧送风+网带载物），最大温差可达13.02℃。

Abstract:

The impingement quick-freezing equipment has higher freezing speed and lower dry loss, but its high speed impinging jet also makes the flow field in the heat transfer zone of the equipment uneven and the energy efficiency of the equipment relatively low. This paper took shrimps as the research object, using the method of numerical simulation combined with experimental verification. The effects of two air supply modes (unilateral air supply and bilateral air supply) and two load modes (plate load and net load) on the freezing process of shrimps were studied, and the air supply and load mode which made the shrimp freezing process shortest was found. It was found that for shrimp freezing, the flow field velocity on the surface of shrimp can be increased by bilateral air supply and net belt load, which was beneficial to improve the heat transfer efficiency and reduce the freezing time of shrimp. Compared with other air supply and loading methods, the freezing time of shrimp can be shortened by 14% to 25%. The bilateral air supply was helpful to form an eddy current to increase the flow velocity on the lower surface of shrimp at the weak side of the air supply. The net load can avoid the formation of jet "vacuum area" at the junction between the lower side of the shrimp and the net belt and the head of the shrimp. Both of them are helpful to increase the surface air speed of shrimp and shorten the freezing time of shrimp. The faster the freezing speed, the worse the freezing uniformity of shrimp. In this experiment, the maximum temperature difference between inside and outside shrimp appeared in experimental group D (bilateral air supply + net load), and the maximum temperature difference was 13.02℃.