Axial and Radial Turbine

Axial and Radial Turbine

AXIAL TURBINE

An axial flow impeller is used to promote a downward velocity profile important
for

  1. Blending of miscible liquids
  2. Solid suspension
  3. Promotion of heat transfer
  4. Incorporating dry powders into liquids

A predominant axial velocity component results as the fluid is drawn in from
above the impeller and forced down to the bottom of the tank. From there the
baffles assist in redirecting the fluid back up the tank walls, resulting in an
efficient top-to-bottom turnover of the product with high flow rates and minimum
shearing action. The interaction between upward and downward streams inherent in
this rolling action is used to blend fluids with viscosities of up to 100,000
cP. Solid suspension is achieved when the rising velocity of the fluid is
greater than the settling rate of the solids. By knowing the particulars of your
product and process needs, Mueller can provide an efficient, economical
solution.

AXIAL TURBINE AGITATION LEVELS

 The table on the following page is based on a single axial flow turbine in a
cylindrical tank with the product height equal to the tank diameter (Z=T) and a
final product specific gravity of 1.0. Presented are possible combinations of
horsepower and shaft speed required to achieve mild, medium, and vigorous levels
of agitation for a range of tank volumes and final product viscosities. Heavier
or more viscous products and different tank volumes and geometries are easily
accommodated.

Mild Agitation – Establishes complete batch motion
with a flat fluid surface sufficient for maintaining product temperature or
blending liquids with similar viscosities and specific gravities.

Medium Agitation – The most common, it produces
surface rippling at lower viscosities, decreases blend time, blends fluids with
large differences in viscosity, and aids in heating or cooling.

Vigorous Agitation – Produces surface surging at
lower viscosities and is required when mixing time is critical or viscosity
differences are great. Often several combinations of impeller diameter and shaft
speed, which in turn determine the required horsepower, will produce the same
level of agitation in the same tank. The correct choice for a particular
application must be based on tank geometry, product characteristics, and cost
considerations.

TURBINE MIXER

The top-entering turbine mixer is the most common form of agitation equipment
used in the process industry. The turbine agitator is an open impeller that may
be thought of as a centrifugal pump without a housing. The impeller is
characterized by 4, 6, or 8 flat blades either pitched at a 45° angle (axial
turbine) or in line with the axis of the shaft (radial turbine). Mueller
incorporates these two common configurations, or any special variation that may
be required, into a system to meet your particular process needs. The flow
pattern induced by a turbine contains three distinct velocity components: axial,
radial, and tangential. The axial and radial components act parallel and normal
to the shaft, respectively. They provide the flow and turbulence necessary for
effective mixing. The tangential component produces a circular pattern or
swirling effect, and must be broken through the use of baffles or off-center
mounting of the shaft in order to provide a desirable flow pattern in the tank.
The impeller type determines the relative magnitude of each component. The type,
number, and rotational speed of the turbine(s) is selected for your particular
application and is readily adaptable to a wide variety of products, processes,
and tank geometries. Mueller will provide the engineering and the complete
agitation package and then install the system in your tank or ours—with a 100%
guarantee of process results.

RADIAL TURBINE

A radial or flat blade turbine is used to promote a velocity profile for

  1. Blending of immiscible liquids
  2. Gas dispersion
  3. Promotion of heat transfer

The fluid is drawn into the impeller area from both the top and bottom in an
axial direction and then discharged radially to the tank wall. At the wall the
fluid is directed down to the tank bottom and up to the fluid surface. The high
shearing action, which results as the flow is changed from axial to radial in
the impeller zones, is required for effective mass transfer in the processes
listed above. Because more torque is needed to deliver this shear, the radial
turbine consumes more power than an axial turbine.

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