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

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℃.