共查询到19条相似文献,搜索用时 78 毫秒
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搅拌槽内粘稠物系的混合过程 总被引:5,自引:0,他引:5
以发酵罐中通气搅拌下的混合为背景,考察了搅拌形式,物系流变性质及通气速率等因素,对搅拌槽内粘稠物质系中混合过程的影响,轴向流翼型混合效率高于涡轮桨,通气有助于改善粘稠物系中的混合粘度变化主要改变槽内流动状态和桨叶泵送能力,从而改变混合效率,当物系为中等粘度假塑性流体时,混合速率由桨叶泵送流动的流量和形态所决定,多层搅拌下分区现象限制了混合速率。 相似文献
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在直径0.48 m的立式搅拌槽内研究了4种组合式螺带搅拌桨的粉体混合性能,考察了搅拌转速、粉体物料装填高度和搅拌桨型对粉体混合性能的影响,分析了径向与轴向上的粉体混合情况. 结果表明,搅拌转速是影响粉体混合的重要因素,增加搅拌转速能明显缩短混合时间,转速44.0 r/min时的混合因子π3比转速8.7及26.5 r/min时下降50%及30%以上;在搅拌桨内部附加较小的内桨使功率略有增加,但可显著缩短混合时间,转速44.0 r/min时能使π3下降50%,提高混合效率. 相似文献
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新型组合桨混合特性研究 总被引:3,自引:0,他引:3
根据聚合反应的特定工艺过程要求,提出了一种新型搅拌桨,对其混合性能进行了研究并与常规桨型进行对比。结果表明,该桨在高粘度流体内混合时间、排液量、混合效率等方面较常规桨型好,能在较短的时间内实现全罐的均匀混合。 相似文献
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多层CBY组合桨搅拌槽内混合特性的研究 总被引:2,自引:0,他引:2
在直径为0.5m的搅拌釜内,采用酸碱中和法测定了多层桨搅拌过渡区的混合时间,应用电导率法测定了湍流区的混合时间,研究了桨叶安放角,桨径,层间距,搅拌雷诺数,桨型对混合特性的影响规律。 相似文献
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针对高固含量木质纤维素同步糖化与发酵生产燃料乙醇过程,研究了螺带型搅拌槽内层流流动条件下少量低粘低密度液体(a)加入大量高粘高密度主体液体(b)中的混合性能,考察了转速、两种液体体积比(Va/Vb)、粘度比(mb/ma)、密度差等影响因素. 结果表明,当Va/Vb>1%时,异物性物系混合时间远高于相同物性液体混合时间,可延长2~5倍;Va/Vb对混合时间影响最显著,Va/Vb=0.2%~3.7%范围内,无量纲混合时间Ntm随体积比增大先降低后升高存在一最小值;当Va/Vb≥2%,单位主体液体密度之差Dr/rb>0.2时,Ntm随着Va/Vb, Dr/rb增加线性增大;Ntm随着mb/ma增大而减小;加入相加在主体液体内所得混合时间比加在液体表面时短;Va/Vb>2%时,混合工况可分为Re数控制区(桨叶控制)及Ri数控制区(重力控制). 相似文献
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采用单个悬浮粒子法和脱色法分别测定了多种不同几何尺寸的螺带式搅拌器的循环时间分布以及混合时间。得到同频度C_5值和混合时间C_1计算式。考察了流体的弹性对循环时间分布和循环流量的影响。 相似文献
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内外单螺带式搅拌器的Metzner常数 总被引:1,自引:0,他引:1
对11种不同向何尺寸的内外单累带搅拌器(IO-HR),在66中不同流动行为指数(n=0.37-1)的幂律流体中的剪切特性进行了实验研究。发现内外单螺带 的Metzner常数,Ks与流动行为指数n、桨的几何尺寸均相关。提出改进的数据处理方法来求算Ks,并详细分析了桨的几何尺寸和流体剪切稀化特性对Ks的影响。最后的对包括经典的Metzner方法在内的不同求解Ks的方法做了分析比较。 相似文献
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The optimal design of close clearance impellers requires the knowledge of the power demand of the mixing equipment. In non‐Newtonian mixing, this can be readily obtained using the Metzner and Otto concept [1]. In this work, this concept and the determination of the Ks value for an atypical helical agitator (PARAVISC system from Ekato firm) have been revised in the case of shear‐thinning fluids and a shear‐thickening fluid. For poor shear‐thinning fluids, it has been shown that for our mixing system the Ks value does not vary strongly with the flow behavior index, and may be regarded as a constant for the mixing purpose design. By contrast, for the shear‐thickening fluid, power consumption measurements indicate that the relationship between the Ks values and the flow behavior index is much more complex due to a partial solidification of the product around the impeller. 相似文献
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A commercial CFD package was used to simulate the 3D flow field generated in a cylindrical tank by a helical ribbon impeller. The study was carried out using a pseudoplastic fluid with yield stress in the laminar mixing region. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure xanthan gum velocity. From flow field calculations and tracer homogenization simulations, power consumption and mixing time results were obtained. The torque and power characteristics remain the same for upward and downward pumping of the impeller, but the mixing times are considerably longer for the downward pumping mode. Overall, the numerical results showed good agreement with experimental results and correlations developed by other researchers. From the power and mixing time results, two efficiency criteria were utilized to determine the best pumping mode of the impeller. 相似文献
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R. P. Chhabra L. Bouvier G. Delaplace G. Cuvelier S. Domenek C. André 《化学工程与技术》2007,30(12):1686-1691
New results on mixing times for viscous Newtonian and non‐Newtonian fluids being homogenized with a helical ribbon impeller are presented. In particular, a recently developed technique to determine the macromixing kinetics of an impeller in a transparent vessel was applied to investigate the effects of rheological properties on mixing times. Significant differences were observed in the mixing times for viscous Newtonian and non‐Newtonian fluids. Based on the new data obtained in this work, a correlation incorporating the elastic effects is proposed in terms of a Weissenberg number for predicting the mixing time as a function of the Reynolds number and the system geometry. 相似文献
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