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Impellers large tanks

Large tanks tend to develop a recirculation pattern from the impeller through the tank back to the impeller. This results in a behavior similar to that for a number of tanks in a series. The net result is that the mean circulation time is increased over what woiild be pre-dic ted from the impeller pumping capacity. This also increases the standard deviation of the circulation times around the mean. [Pg.1625]

The shear stress in the fluid is much higher near the impeller than it is near the tank wall. The difference is greater in large tanks than in small ones. [Pg.1629]

The fluidfoil impellers in large tanks require only two baffles, but three are usually used to provide better flow pattern asymmetiy. These fluidfoil impellers provide a true axial flow pattern, almost as though there was a draft tube around the impeller. Two or three or more impellers are used if tanks with high D/T ratios are involved. The fluidfoil impellers do not vortex vigorously even at relatively low coverage so that if gases or solids are to Be incorporated at the surface, the axial-flow turbine is often required and can be used in combination with the fluidfoil impellers also on the same shaft. [Pg.1631]

Similarly, that is true for the rotational speed of large tank, which is related to a small tank with the ratio of impeller diameter of large and small tanks to the power of 2/3. [Pg.288]

FIGURE 15 Schematic illustration of the increase in maximum impeller zone macroscale shear rate and a decrease of average impeller zone macroscale shear rate as tank size is increased, illustrating a wider distribution of shear rates in a large tank than in a small tank. The figure is based on a constant power/volume ratio and geometric similarity between the two tanks. [Pg.288]

Substituting the impeller diameter in meters gives 107.2 r/min for the large tank and 146.8 r/min for each small tank. The Reynolds numbers... [Pg.164]


See other pages where Impellers large tanks is mentioned: [Pg.336]    [Pg.425]    [Pg.230]    [Pg.1631]    [Pg.563]    [Pg.291]    [Pg.311]    [Pg.177]    [Pg.46]    [Pg.83]    [Pg.98]    [Pg.549]    [Pg.65]    [Pg.253]    [Pg.177]    [Pg.288]    [Pg.295]    [Pg.563]    [Pg.449]    [Pg.164]    [Pg.336]    [Pg.1452]    [Pg.1776]    [Pg.1949]    [Pg.14]    [Pg.336]    [Pg.90]    [Pg.188]    [Pg.1770]    [Pg.1937]    [Pg.549]   


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