Macro level mixing - Physical processing
Macro-level mixing topics covered in this category are mixing or blending times
based on several different methods. Acid-base neutralization with an indicator makes mixing or blend
time studies visible to the naked eye and allows the investigator to see the location of the
worst mixing. Mixing paints or dyes can also be used to determine mixing times, but because these
are usually opaque, the determination of the mixing time is restricted to what you can see at the
tank wall, or during the draining of the tanks contents. Other mixing studies are done with
ionic conductivity, radioactive tracers, density difference (stratified mixing layers), or
pH which are not visible. Since they require instrumentation, they should belong in the
micro-level mixing topics, but because mixing time studied based on acid-base neutralization
are so colorful and visible, all mixing and blend time studies are grouped here. Residence time
distributions of continuous processes (including continuous stirred tank reactor models, CSTR)
also belong here as well as the resulting characteristics such as back mixing,
short circuiting and dead zones. Typical reactor studies in chemical and mechanical engineering
just talk about perfect mixing and plug flow models. Studies describing imperfect mixing, which
probably describes 90% of all industrial mixing applications, belong here.
Examples:
Mixing in from the surface: Click here to see a simulation of the
mixing effects of a pitched bladed turbine. The objective is to study the blending of a miscible
fluid from the surface with the rest of the fluid in the tank. The fluid has water-like
properties. The animation is over 5000 KB large so it may take some time to download.
Mixing in from the bottom: Click here to
see a simulation of the mixing effects of a pitched bladed turbine. The objective is to study the
blending of a miscible fluid from the bottom of the tank with the rest of the fluid in the tank.
The fluid has water-like properties. The animation is over 5000 KB large so it may take some
time to download.
We are currently working on other pages of the Mixing Forum. This page will be updated shortly.
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