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1.
本文研究了层流区域有较大叶片截面积的特型双螺带──锚桨叶在高粘弹性和非弹性流体中的搅拌功率,测定了K_p和K_s,采用广义二阶流体本构方程导出搅拌功率计算式参数f_s和F_(1ac)由实验数据确定。该式适用于牛顿型流体、假塑性和粘弹性流体的功率消耗计算。  相似文献   

2.
The influence of the stirrer type and of the geometrical parameters of both tank and agitator (clearance of an impeller from tank bottom, impeller diameter, draft tube and geometry of the tank bottom) on power consumption and mixing time in liquid phase under turbulent regime conditions (Re > 104) have been studied. Different types of agitators have been used, namely Rushton turbine, 45° pitched‐blade turbine, MIXEL TT and TTP propellers and 1‐stage or 2‐stage EKATO‐INTERMIG propellers. All these stirrers were tested with the same power consumption per unit mass of liquid. On the basis of measured power consumption per unit mass, which is required to achieve the same degree of mixing, the results obtained in the present work show that the TTP propeller is the most efficient in liquid phase. Recommendations on the optimum geometric configuration have been made for each type of stirrer.  相似文献   

3.
The dependence of power consumption on impeller spacing in unaerated and aerated gas‐liquid contactors agitated by dual Rushton turbine systems was studied, and the gas flow rate and viscosity effects were measured in relation to these parameters. The experiments were carried out in a 0.19 m i.d. vessel stirred by two Rushton turbines with a diameter d = 0.10 m; with blade length and blade height 0.25 d and 0.2 d, respectively. In tap water the impellers acted independently for spacings greater than 1.65 d, while in glycerol solutions the two impellers already acted independently at an impeller spacing equal to 1.2 d. In aerated systems, a notable increase in the power consumption with increasing impeller spacing could be detected for small gas flow rates and low viscosities, while a decrease in the Newton number with increasing Froude number could be observed at constant impeller spacing. The Newton number was not affected by flow number at high viscosity values.  相似文献   

4.
The influence of impellers and baffles on the mixing of gas‐liquid floating particles in agitated vessels was investigated. Fifty‐two kinds of impeller combinations and twelve types of baffle arrangements were used. The associated power, gas holdup and solids concentration at the vessel bottom were measured. It is concluded that the mixing characteristics of three‐stage impellers were superior to those of two‐stage impellers for aspect ratios larger than 1.6. The optimal combination of impellers and baffles was proposed. The correlations of the relative power and the gas holdup for the optimal combination of impellers under all types of baffles were obtained.  相似文献   

5.
A melt‐phase polymerization reactor with the novel geometry of two helical solid‐tube impellers rotating within a tank, consisting of two intersecting cylinders, was designed and constructed. In order to evaluate the performance of the system, mixing times and power consumption were measured using a viscous Newtonian model fluid (glucose syrup) in place of the polymer melt. The mixing regime was laminar in all runs. The mixing time at various impeller speeds was estimated by injection of a tracer dye (crystal violet), followed by fluid sampling and visible spectrophotometric analysis. A dimensionless mixing time of km = 104 ± 36 was obtained. The power draw required to move each impeller through the fluid at various impeller speeds was measured, and a power constant of kp = 1156 ± 70 was obtained. The system appeared to outperform the conventional single helical ribbon impeller in terms of mixing time, but was less energy‐efficient, as indicated by the larger power constant. The power constant value lies between values previously reported in the literature for conventional helical impellers and values reported for other types of polymerization reactors with different geometries.  相似文献   

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An organocatalytic quadruple domino reaction initiated by a Friedel–Crafts‐type reaction of electron‐rich arenes is described. The procedure involving up to three different Michael acceptors afforded highly functionalized cyclohexenecarbaldehydes bearing an aniline moiety, which are of great pharmaceutical and agricultural interest. This diphenylprolinol trimethylsilyl ether‐catalyzed reaction also generates up to 4 contiguous stereocenters. It could be shown that various functional groups are tolerated and all products were obtained with very good diastereo‐ and excellent enantioselectivity.  相似文献   

9.
Feeding ewes a diet high in n‐6 in late gestation can affect fatty acid concentrations in the newborn lamb. The effect of feeding ewes a high n‐6 diet prior to conception and in early gestation on lamb n‐6 and n‐3 status has not previously been examined. The aim of the current study was to determine whether the concentration of n‐6 was higher and n‐3 was lower in lamb red blood cells (RBC) and plasma when Merino dams were fed a diet high in n‐6 either pre‐conception only or both pre‐conception and in early gestation. Dams were fed a diet low (silage) or high (oats/CSM) in n‐6 for either 6 weeks pre‐mating only or 6 weeks pre‐mating and 17 days post‐mating. The fatty acid status of lamb RBC and plasma was determined following birth and compared with dam fatty acids around parturition. The concentration of lamb RBC and plasma n‐3 was lower (p < 0.05) when dams received the high n‐6 compared with low‐n‐6 diet around mating, independent of the length of time of feeding. The concentration of n‐3 in lamb plasma was also higher when lambs were assessed as being likely rather than unlikely to have suckled prior to blood collection. Lamb RBC and plasma n‐3 fatty acids were lower when dams were fed the high compared with the low n‐6 diet for only a short time around mating. Transfer of fatty acids via the placenta and milk may account for the differences.  相似文献   

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