Can you explain a question about the Thien baffle?

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Forum topic by JerryinCreek posted 07-30-2014 06:06 PM 982 views 1 time favorited 2 replies Add to Favorites Watch
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211 posts in 1835 days

07-30-2014 06:06 PM

I’m about to begin my build of a chip separator with a Thien baffle. I’ve done quite a bit research to satisfy my design needs, but I’m still left with a question. I can’t figure out why the vacuum from the center connection doesn’t just directly suck up the dust coming out of the input elbow?

(Guess they call it a baffle because it baffles me!)

-- Jerry, Johnson Creek, WI "If it was meant to be different it would be."

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4030 posts in 2965 days

#1 posted 07-30-2014 07:39 PM

In both a Thein Baffle system and a true cyclone the dust and air enters through an elbow that directs the flow against, and tangent to, the outside circumference of the container.

In a true cyclone the diameter of the circumference starts to get smaller as the flow goes down the wall of the cone. Gravity causes the flow to travel down the container wall and centrifugal force holds the flow against the container wall. The flow increases speed as the cone circumference gets smaller and at the bottom of the cyclone the flow drops below the bottom of the cone and into the larger dust container where the centrifugal force keeps the dust against the walls of the dust container while the spinning vortex of air tightens up and travels up the center of the cyclone and exits through the center tube. Because the vortex gets smaller and smaller the speed gets to be so high the dust can not keep up with the much lighter air. Think of an ice skater spinning that pulls their arms in close to their body; their speed increases. Then they spread their arms out and the speed decreases.
The body of the skater is the air flow and the arms act like the dust. When the dust spreads out into the larger container it slows down while the air continues to accelerate in an ever tighter circle.

In the Thein Baffle system, the baffle serves the same function as the bottom of the cone where the flow enters the dust hopper. The spinning flow is pushed against the walls of the container and has to speed up to squeeze through the relatively small slot. After passing through the slot the flow is in the dust container section and the air flow has to continue to spin in a tighter circle to get back to the center and exit up the center tube. The high speed spinning is what keeps the dust from getting back to the center of the vortex. It is just too heavy to spin that fast so it drops to the bottom of the hopper.

This principle is used in lots of processes to separate different size and weight of particles.

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211 posts in 1835 days

#2 posted 07-30-2014 07:44 PM

Thank you very much! I knew somebody out there would have the answer. Much appreciated!

-- Jerry, Johnson Creek, WI "If it was meant to be different it would be."

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