Fractal Mixing and Fractal Reactors
Fluid mixing is a process which involves scaling of the fluids involved (scaling from large to small) and, further, the intermingling of the fluids. In most conventional mixing, this is accomplished via turbulence. While a number of features characterize turbulence, of particular interest are the irregularity and energy dissipation characteristics. The turbulent phenomena is uncontrollable and highly non-symmetric. Turbulence dissipates as the kinetic energy is converted into internal energy by viscous shear stress.
Fractal mixers and reactors maximize symmetry and predictability
Unlike turbulence inducing equipment, ARi fractal mixers and fractal reactors are designed to maximize symmetry and minimize the unpredictable characteristics of mixing. Furthermore, the energy dissipation feature observed with turbulence is significantly reduced. Rather than using uncontrollable turbulent fluid collisions, ARi fractal mixers and fractal reactors use precise engineered channeling to accomplish both scaling and intermingling.
Note that fractal mixers have certain characteristics which are analogous to turbulence. For example, a turbulent flow consists of eddies over a wide range of length scales. In place of the eddy cascade, a fractal mixer consists of a hierarchy of channels, also over a wide range of length scales. Designing extreme symmetry into the fractal devices drastically reduces energy use, improves process efficiency, provides a much clearer understanding/analysis of the process and enables a wide variety of useful functions not possible with turbulence oriented mixers and reactors.
Fluid property distributions are controlled with the use of ARi fractals. Distributions which can be controlled favorably include velocity, temperature, concentration, eddy size, bubble size, etc. This control results in smaller and more efficient processes.
Because components to be mixed and/or reacted do not contact one another until scaling and distribution is completed, large scale process inhomogeneities, side reactions, etc. can be entirely eliminated.
Because the final fluid contact volume can be extremely small, it is possible to alter many mixing and reaction conditions (such as pH or temperature) in a near instantaneous manner.
While general uses for the devices include mixing and/or reaction of two or more fluids, there are a large variety of other processing possibilities. For example, several rapid and sequential mixing/reacting steps can easily be configured. As another example, the devices can be used for larger scale mixing prior to final small scale turbulent mixing/reaction. In this case, advantage can be taken of the beneficial smallest scale characteristics of turbulence.
Some applications for fractal reactors and mixers include:
- Liquid-liquid mixers/reactors.
- Gas-gas mixers/reactors.
- Liquid-gas mixers/reactors.
- Multi-phase reactors.
- Combustion mixers/reactors.
Because fractals are, by definition, scaling structures, fractal mixers and fractal reactors can be evaluated on a small pilot scale and reliably scaled up to any desired industrial size. ARi has designed and operated fractal mixer/reactors from lab benchtop scale to industrial devices exceeding 15 feet diameter, with input flowrates exceeding 21,000 gpm.
ARi uses a variety of computer aided techniques to design and construct fractal mixers and fractal reactors. Materials of construction are selected by the customer for application specific compatibility.