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Characteristics of turbulence energy dissipation and liquid-liquid dispersions in an agitated tank.

机译：搅拌槽中湍流能量耗散和液-液分散的特征。

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This thesis covers two major fields in mixing: turbulence energy dissipation and liquid-liquid dispersions in agitated tanks. The main objective of the thesis was to examine the effect of tank and impeller geometry on these variables.; The average turbulence energy dissipation in the impeller regions was investigated for three impellers (the Rushton turbine (RT), the pitched blade turbine (PBT) and the fluidfoil turbine (A310)) using the macroscopic mechanical energy equation. The majority of the input power is dissipated in the small volume of the impeller region for all three impellers. Analysis of the distribution of energy between convective and turbulent flow shows that the A310 is the most efficient at generating convective flow; the RT generates the most turbulence kinetic energy and the PBT derives a large portion of its energy from the return flow.; The equation ({dollar}varepsilon{dollar}=Av{dollar}sp3{dollar}/L), used to estimate the local turbulence energy dissipation rate, was verified by comparing local and integral methods. Here v is a fluctuating velocity; A is a constant and L is macroscale length. The effect of rank geometry (number of baffles (N{dollar}sb{lcub}rm f{rcub}{dollar}), impeller diameter (D), and off bottom clearance (C or C/D)) on {dollar}varepsilonsb{lcub}rm max{rcub}{dollar} was investigated using three factorial designs for four impellers (PBT, A310, HE3 and RT). The dominant variable was shown to be the impeller diameter. This effect is in addition to the expected scaling with D{dollar}sp2.{dollar} Clearance is also an important variable, which is best quantified by its dimensionless form, C/D. The number of baffles has no significant effect on {dollar}varepsilonsb{lcub}rm max{rcub}.{dollar}; Silicone oil/water dispersions were also studied with varying tank geometries. The shape of the drop size distribution changes with rotational speed (N). Four characteristic distributions were found; in order of increasing N: long tail, double peak, skew, and skew-normal distribution. Two normal distributions can be combined to represent the last three distributions. The Kolmogoroff length scale ({dollar}eta{dollar}) cannot be used as an estimate of the minimum drop size present in the dispersions investigated. The cumulative number probability density less than {dollar}eta{dollar} is negatively correlated with {dollar}varepsilonsb{lcub}rm max{rcub}.{dollar} The Sauter mean diameter (d{dollar}sb{lcub}32{rcub}){dollar} is more closely correlated to {dollar}varepsilonsb{lcub}rm max{rcub}{dollar} and the interaction of {dollar}varepsilonsb{lcub}rm max{rcub}{dollar} with the mean flow than to P/{dollar}rho{dollar}V{dollar}sb{lcub}rm T{rcub}.{dollar} A new correlation for d{dollar}sb{lcub}32{rcub}{dollar} is proposed.
机译：本文涵盖了搅拌的两个主要领域：湍流能量耗散和搅拌槽中的液-液分散。本文的主要目的是研究罐和叶轮几何形状对这些变量的影响。使用宏观机械能方程研究了三个叶轮（Rushton涡轮机（RT），变桨叶片涡轮机（PBT）和翼型涡轮机（A310））在叶轮区域中的平均湍流能量耗散。对于所有三个叶轮，大部分输入功率消耗在叶轮区域的小体积中。分析对流和湍流之间的能量分布表明，A310是产生对流最有效的方法。 RT产生最大的湍动能，而PBT从回流中获得很大一部分能量。通过比较局部方法和积分方法，验证了用于估计局部湍流能量耗散率的方程式（$ varepsilon {dollar} = Av {dollar} sp3 {dollar} / L）。这里v是脉动速度； A为常数，L为宏观长度。等级几何形状（挡板数（N {dollar} sb {lcub} rm f {rcub} {dollar}），叶轮直径（D）和底部间隙（C或C / D））对{dollar}的影响varepsilonsb {lcub} rm max {rcub} {dollar}是针对三个叶轮（PBT，A310，HE3和RT）使用三因子设计进行研究的。主要变量显示为叶轮直径。此效果是对D {dollar} sp2的预期缩放的附加作用。间隙也是一个重要变量，最好用其无量纲形式C / D进行量化。挡板的数量对{dollar} varepsilonsb {lcub} rm max {rcub}没有明显影响。{dollar};硅油/水分散体的罐几何形状也进行了研究。液滴尺寸分布的形状随着转速（N）而变化。发现了四个特征分布。按N递增的顺序：长尾，双峰，偏斜和偏正态分布。可以组合两个正态分布以表示最后三个分布。 Kolmogoroff长度标度（{dollar} eta {dollar}）不能用作对所研究分散体中最小液滴尺寸的估计。小于{dollar} eta {dollar}的累积数概率密度与{dollar} varepsilonsb {lcub} rm max {rcub}负相关。{dollar} Sauter平均直径（d {dollar} sb {lcub} 32 {rcub }）{dollar}与{dollar} varepsilonsb {lcub} rm max {rcub} {dollar}的相关性更高，并且{dollar} varepsilonsb {lcub} rm max {rcub} {dollar}与平均流量的相互关系比与P / {rho {dollar} V {dollar} sb {lcub} rm T {rcub}。{dollar}提出了d {dollar} sb {lcub} 32 {rcub} {dollar}的新相关性。

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