Square or Rectangle Top Hat Inlet

[retired2]

Actually the eccentric model is the most efficient in regards to the inlet. Because here is what happens, when the incoming air is introduced into the separator with a round inlet there is something you may have not noticed. Look at the videos of Pitbull's 6" inlet/outlet that he has posted that show him demonstrate his inlet. You will see a "before" video with his inlet protruding just a bit inside the separator and as he feeds it dust, you will see the turbulence as the debris is hitting the incoming air and bouncing back through the inlet. Then watch his "after" video and you will see where he tries to cut back on the inlet material, but again, during his demonstration, there is still the turbulence. The factors involved were twofold.
First, the inlet material was protruding inside the separator causing the air and debris that is being "cycloned" to smash against it.
Second, because of the round inlet being introduced into a "cyclone" environment the outside 2 corners facing the opposite side of the inlet are causing a depression in the cyclone action.
With a eccentric transition into the inlet it prepares the incoming air for the cyclone that is happening inside of the separator by removing the corners and therefore removing the depressions in the cyclone. One of the main reasons I feel that a "scroll" method would benefit in this is because it helps introduce the incoming air and debris into the cyclone with the least amount of turbulence and therefore enhancing separation. My 2 cents.

Don,

Are we talking about the same thing?  Here is sketch of what I meant by eccentric transition.  The eccentric version has the centerline for the rectangular end offset from the circular end so that the outside wall is on the same plane.  The concentric version has a single centerline with equally converging sides.

[Don_Z]

The Rectangular port is what is connecting to the actual separator. A round inlet causes the depression/ turbulence.

[retired2]

The Rectangular port is what is connecting to the actual separator. A round inlet causes the depression/ turbulence.

I agree, but which of the two transition pieces I've drawn do you think would be better.  Both sketches go from round to rectangular where it connects to the separator.  I first thought the eccentric version might be better, but I'm no longer sure.   The reality is it might not make any difference which configuration I use.

[bumpnstump]

Not sure I'm smart enough to understand all of the science of this, but here's what I did:
-I built my separator using a scroll inlet, allowing for a 4" round inlet on the side, 2" offset scroll, with a 4" outlet in the top.  With pipe hooked straight up to the 4" round inlet, I was getting lots of bypass.
-Then, after reading thru some of Bill Pentz's articles, I decided to build a round-to-rectangular transition piece.  Following his instructions, I built a 12" long x 4" round to (in my case) a 2 3/4"w x 4 5/8" h rectangular transition.
-After installing and using it, there is very little-to-no bypass.
I'm not even sure what/if I did correct, only that it made a big difference.
Hope this is helpful.
Thanks,
Rick

[retired2]

Not sure I'm smart enough to understand all of the science of this, but here's what I did:
-I built my separator using a scroll inlet, allowing for a 4" round inlet on the side, 2" offset scroll, with a 4" outlet in the top.  With pipe hooked straight up to the 4" round inlet, I was getting lots of bypass.
-Then, after reading thru some of Bill Pentz's articles, I decided to build a round-to-rectangular transition piece.  Following his instructions, I built a 12" long x 4" round to (in my case) a 2 3/4"w x 4 5/8" h rectangular transition.
-After installing and using it, there is very little-to-no bypass.
I'm not even sure what/if I did correct, only that it made a big difference.
Hope this is helpful.
Thanks,
Rick

Thanks Rick.  Your comments are indeed helpful.  They confirm that a rectangular inlet, higher than it is wide, is the probably the best inlet port.  The discussion about eccentric vs concentric transition might have been a little hard to follow since I had a bad link to my sketch.  I've corrected that and now you can see what I was talking about above.  Was your transition piece eccentric or concentric?

Also, if you don't mind, what was the inside diameter of your separator?  I'm building a 5" inlet/outlet separator and I was planning to put it on a 20 gal Brute, but Phil was a little concerned that the resulting ID might cause some bypass.  I am now planning to use a Brute 33 gal, but that makes everything a little larger than I wanted.

Thanks

[bumpnstump]

Retired,
I built the transition eccentric, but because the dimensions at each end are close to the same, it's a bit tough to determine that it's built that way.
I built the seperator to an existing drum that I had sitting around:  ~16" diam.
Rick