速冻机宽度方向上流场的实验分析

Analysis of the Experiment of the Flow Field along the Width Direction of a Quick Freezing Machine

在速冻机宽度方向上,速冻机两侧的冻品冻结速率远大于速冻机中心,为解决速冻机宽度方向上冻品冻结速率不均匀的问题,通过实验分析沿速冻机宽度方向上冻结速率差别较大的原因及速冻区域内气流的稳定性。研究表明：在速冻机宽度方向上,速冻机中心流速最低,两侧流速最高;靠近压力出口,喷嘴出口流速为19.11 m/s;远离压力出口,喷嘴出口流速为14.03 m/s。测点S_1、S_2、S_3和S_4的速度不均匀度为32%、99.92%、31.81%和79.62%。速度不均匀度是引起冻结速率不同的关键因素。速冻区域内气流的不稳定性会削弱换热,降低冻结速率,测点S_1、S_2、S_3和S_4的速度极差数值反映了气流的波动性。波动性最小的是S_1点,极差最小值为0.69 m/s。

In the width direction of a quick freezing machine, the freezing rate of the frozen products at both sides of the quick freezing machine is far greater than that in the center of the machine. To solve the problem of non-uniformity of the freezing rate of frozen products along the width direction of the freezing machine, through a test, the causes for such a big difference in the freezing rate along the width direction of the freezing machine was exporatorily studied and at the same time, the stability of the gas flow in the quick frozen zones was also analyzed. It has been found that along the width direction of the quick freezing machine, the flow speed in the center of the quick freezing machine is the lowest while those at both sides are the highest. Nearing the outlet,the flow speed at the outlet of the nozzle is 19.11 m/s. At places far away from the outlet, the flow speed at the outlet of the nozzle is 14.03 m/s. The non-uniformity of the flow speeds at the measuring points SI ,Sz ,S3 and S4 are 32.00% ,99.92% ,31.81% and 79.62% respectively. The instability of the gas flow in the quickly frozen zones will weaken the heat exchange and lower the freezing rate. The value of the extreme difference of the flow speeds al the measuring points S1 ,S2 ,S3 and S4 will reflecl the fluctuation of the gas flow. The mininmm fluctuation is located at the measuring point S1 and tile minimum extreme difference is 0.69 m/s.