喷嘴出口流速与钢带表面换热特性的CFD模拟

CFD Simulation of Flow Characteristics at Nozzle Outlet and Heat Transfer on Steel Strip Surface

以条缝喷嘴的上下冲击式速冻机为对象,建立了包括静压腔、条缝喷嘴、钢带和导风槽在内的三维数值模型进行CFD模拟,并对速冻机特征位置的风速进行了试验测试,结果验证了数值模拟的可行性。同时探讨了结构参数对喷嘴出口速度和钢带表面换热特性的影响,结果表明:沿速冻机宽度方向,喷嘴出口流速变化较大,距离压力出口越远,喷嘴出口流速越小,在速冻机中心到达最低;随着Hs增加,沿速冻机宽度方向喷嘴出口流速均匀性逐渐改善;沿速冻机宽度方向,钢带表面Nu呈现不均匀分布,当Hs=2时,换热不均匀度为33.1%;随着Hs增大,Z方向喷嘴出口流速增加,钢带表面Nu减小;根据虾仁不被吹飞的临界横向风速及虾仁表面最大换热强度确定了喷嘴出口与钢带之间的最佳Hs=10。

The three-dimensional numerical simulation CFD model,which includes the static pressure cavity,slit nozzle,steel strip and air guide groove of quick freezer was established to research the air flow characteristics and heat transfer on the steel strip surface. The velocity of the key point in the frozen area was measured to verify the feasibility of the CFD simulation. The test results show that the simulation model is reasonable. In the research it was also discussed whether the structure parameter could affect the nozzle outlet velocity and the heat transfer characteristics of the steel strip surface. The results show that the nozzle outlet velocity was greatly affected by the width direction of the quick freezer. The farther away from the pressure outlet,the smaller the velocity of the nozzle outlet,and the velocity reaches the minimum value at the quick freezer center. With the increase of Hs,the velocity uniformity of the nozzle outlet was gradually improved along the width direction of quick freezer and the nozzle outlet velocity in Z direction was increased. However,the Nu number on the steel strip surface showed non-uniform distribution. When Hs=2,the uniformity of heat transfer was 33.1%.As Hs increased,the outlet velocity at nozzle outlet in Z direction increased,Nu number on steel strip surface decreased. According to the critical lateral crossflow velocity at which the shrimp meat was not blown away and the maximum heat transfer intensity on the steel strip surface,the optimal Hs between nozzle outlet and the steel strip was 10.