顶入式与侧入式搅拌槽内混合特性的比较

应用计算流体动力学方法(CFD)对顶入式与侧入式搅拌槽内的流型特征、混合过程进行了数值模拟。计算采用标准k-ε湍流模型、多重参考系法和滑移网格法研究了2种形式搅拌槽的混合效率,分析了不同槽高径比H/T及桨型对侧入式搅拌槽混合性能的影响,并使用文献数据与碘一硫代硫酸钠褪色法对模拟进行了验证。结果表明:四斜叶开启涡轮桨(PBTD45)运行下顶入式与侧入式搅拌槽内主体循环均是轴向循环流;在H/T=1的搅拌槽中相同功耗情况下,顶入式搅拌的混合效率比侧入式搅拌的高,混合时间减少了约28.2%;侧入式搅拌在较低H/T比的搅拌槽内的混合效率较高,当H/T=0.6左右时侧入式搅拌的混合效率与顶入式(H/T=1)接近。PBTD6030桨与FE-4桨较适合侧入式搅拌槽中的混合操作。

Mixing performance comparison between top entry impeller and side entry impeller in stirred tanks

Computational fluid dynamics(CFD) method was used to study the flow field and mixing process in stirred tanks equipped with top entry impeller and side entry impellers.The standard k-εturbulent model,multi-reference frame and sliding grid methods were used in the simulation.The mixing performances of top entry impeller and side entry impellers were analyzed.Simulation results were validated by the fade method for iodine-sodium thiosulfate and reference data.The effect of tank height-diameter ratio, H/T,and impeller type on mixing time in side entry stirred tank were investigated.It was found that the main circulation loops in both the top entry and side entry stirred tanks equipped with pitched blade agitators(PBTD45 ) were axial loops.In the stirred tanks(H/T=1 ),the mixing performance of top entry mixer was better than that of the side entry on the same power consumption and the mixing time reduced about 28.2%.For the side entry mixer,the mixing performance was better when H/T was lower.The mixing efficiency was the same as that of top entry mixer(H/T = 1 ) when H/T ratio of side entry stirred tank was approximately 0.6.The PBTD6030 and FE-4 impellers were suitable for the mixing operation in side entry stirred tanks.