Agitating – Stationary deflector in flow-through mixing chamber – Curved deflector surface
Reexamination Certificate
2000-06-08
2001-12-18
Cooley, Charles E. (Department: 1723)
Agitating
Stationary deflector in flow-through mixing chamber
Curved deflector surface
C138S177000, C165S163000
Reexamination Certificate
active
06331072
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device, in particular for mixing, for heat exchange or for carrying out reactions, having one or more through-flow elements which have a center line in the direction of flow. Devices of the said type are known, specifically as continuous, chaotic convection mixers or convection heat exchangers or convection reactors for Newton and non-Newton fluids.
In addition, a multiplicity of types of mixer/heat exchanger are also known. Static mixers have stationary built-in components at which the mixing operation is accelerated. In other types of mixer (mixing vessel, agitated tubular reactor), the mixing is undertaken by movable built-in components. Chaotic mixers and heat exchangers (J. Fluid Mech., 1989, Vol. 209, pp 335-357, Experimental Thermal and Fluid Science, 1993, Vol 7, pp 333-344, Wo 94/12270) use the secondary flows induced by inertia in curved tubes or channels for the purpose of mixing.
In the case of static mixers, recirculation zones can lead to deposits on the built-in components. Furthermore, overheating of the fluid (hot spots) can occur locally in the recirculation zones. Mixing systems with moving built-in components have the disadvantage that they are of more complicated construction than static mixers. As a rule, they require a drive and a controller. In the case of complex thermal and rheological fluids, effects such as local overheating and degradation of the fluid can occur because of the high shear rates at the agitating elements. In the known chaotic mixers (WO 94/12270), separation regions can occur on the basis of the flow guidance in the case of relatively large volumetric flows. It is then possible for deposits and local overheating to occur in said recirculation zones.
SUMMARY OF THE INVENTION
It was therefore the object of the invention to find a device of the type mentioned at the beginning which requires no built-in components and can be built simply and compactly. Furthermore, the aim is to be able to achieve a good mixing and heat exchanging effect—without the disadvantages discussed above—over a wide range of viscosity and volumetric flow.
This object is achieved according to the invention by means of a device of the type mentioned at the beginning, wherein the through-flow element(s) is/are at least partially shaped or arranged such that the curve formed by the center line(s) approximately satisfies the following parametric representation:
ϑ
(
t
)
=
(
(
-
1
)
[
t
]
a
(
t
)
(
cos
(
2
π
t
)
-
1
)
c
(
t
)
t
a
(
t
)
sin
(
2
π
t
)
)
the parameters and constants having the following meaning:
∂(t) position vector in a Cartesian coordinate system,
t parameter along the curve (
9
), −∞≦t≦+∞,
[t] integral fraction of t,
a(t) a radius of curvature (
10
), where 0<|a(t)|<∞,
c(t) a spacing parameter, where 0<|c(t)|<∞.
The subject matter of the invention is thus a device, in particular for mixing, for heat exchange, or for carrying out reactions, having one or more through-flow elements which have a center line in the direction of flow, wherein the through-flow element(s) is/are at least partially shaped or arranged such that the curve formed by the center line(s) approximately satisfies the following parametric representation:
ϑ
(
t
)
=
(
(
-
1
)
[
t
]
a
(
t
)
(
cos
(
2
π
t
)
-
1
)
c
(
t
)
t
a
(
t
)
sin
(
2
π
t
)
)
the parameters and constants having the following meaning:
∂(t) position vector in a Cartesian coordinate system,
t parameter along the curve (
9
), −∞≦t≦+∞,
[t] integral fraction of t,
a(t) a radius of curvature (
10
), where 0<|a(t)|<∞,
c(t) a spacing parameter, where 0<|c(t)|<∞.
In this case, a parameter range t for a through-flow element defines a so-called loop of 360° from one whole number to the next whole number, and a double loop to the next whole number but one.
A device is preferred which is composed of several loops. Connection of the loops can be produced by means of methods known to the person skilled in the art for detachable (flanges) or undetachable (welding, soldering) connections. It is also possible for the individual loops to be interconnected via known connecting pieces, straight or curved tubes. As many different devices according to the invention as desired can be produced in this way. a(t) and c(t) can vary or be the same along the curve or from loop to loop in such a device. In a preferred embodiment, one or each through-flow element and/or one or each loop satisfies the parametric representation exactly or partially exactly or completely.
Also preferred is an embodiment in which the through-flow elements are shaped or arranged such that the curve formed by the center line(s) satisfies the parametric representation over the entire device. The through-flow elements or the loops preferably have a circular, rectangular or elliptical cross section. They do not lie in one plane in space, but are arranged in space progressively, one behind another. The center line can be a line of symmetry as regards to the cross-sectional area. In the case of symmetrical or approximately symmetrical cross sections, curves which interconnect identical sites on the circumference of individual through-flow elements in the direction of flow, for example specific comers of individual elements in the case of square elements, are to be considered as equivalent to the curve from the center lines, i.e. said curves (edges in the direction of flow) likewise satisfy the parametric representation. Slight deviations of the curves from the parametric representation, particularly within the scope of normal production and/or assembly tolerances, are not deleterious.
The device can consist of one piece or be composed of several parts. The design and production can be performed in accordance with the well-established methods. As materials, consideration is given to all metallic or nonmetallic materials familiar to the person skilled in the art, depending on the design and type of the flowing fluids: plastics, steels (stainless or acid-resistant), glass, ceramic or special materials.
The multiples of the diameter of the tube specified in German DIN 2605 T1 are preferably used as radii of curvature a(t) of the center line. A typical design consists, for example, of a tube with the outside diameter D=40 mm. Design 5 of the standard uses a bending radius of 100 mm. A lead (spacing parameters c(t)) of 100 mm per loop of 360° then proves to be advantageous. The number of loops is determined by the mixing task. A typical number of loops is 4 to 8. The wall thicknesses d are usually in the range from 0.5 to a few mm, in the case of extreme pressures up to 10 mm and more. In particular embodiments, the or each through-flow element has an outside diameter D in the range from 1 to 200 mm, preferably 5 to 100 mm, particularly preferably 10 to 50 mm, and the radius of curvature a(t) is selected from the range from 1*D to 7*D, preferably 2*D to 5*D. The spacing parameter c(t) is advantageously selected from the range from −20*D to +20*D, preferably −10*D to +10*D, particularly preferably from −5*D to +5*D, it being the case that it is always ≠0.
The advantages of the device according to the invention are to be seen essentially in that it is of simple design and easy to produce, and in that no separation regions occur in the flow guidance. A further important advantage is that a very compact design is produced on the basis of the law of formation. By contrast with static mixers with built-in components, the device according to the invention can be cleaned easily, for example using go-devils. By contrast with the chaotic mixer disclosed in WO 94/12270, the device according to t
Hein Peter
Lauschke Götz
Ott Stefan
Schierholz Wilfried
Schmidt Ulrich
Axiva GmbH
Connolly Bove & Lodge & Hutz LLP
Cooley Charles E.
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