HF DC spiral collector with flow redirection

[nucww]

Copied from inline separator.
Most of the design and credit comes from the contributors of the topic:5", Rectangular Inlet, Bellmouth Outlet with Air Straightener, Top Hat Separator.
This is being used with a HF DC so the design was trying to minimize pressure drop to maximize flow.
Some of the significant differences are:
-  spiral chamber with the spiral starting ~6" before chamber entry.  The spiral lost ~2 1/4" per revolution.
-  a high narrow rectangular inlet (10"x2.25") so that entry dust is already close to the outer surface
-  Plexiglas on the top and formica for the spiral sides
-  Baffle slot was extended to ~320 degrees since the spiral design should minimize turbulent entrance.
-  a 3/4" MDF baffle with the slot edges tapered to ~1/4".
-  5" outlet pipe with a X flow straightener
-  a commercial bellmouth outlet pipe with the flat part of the rim cut off resulting in ~7.25" OD mouth for a 5" base pipe
-  flow diverters at the bottom of the wide mouth to divert the flow up rather than spinning around. Some CFD simulations show that vortex in the center is huge and is likely causing significant pressure losses.
I had a anemometer to measure airspeed to test some of the differences.
With the standard HF setup, 10' HF flex pipe and a 4" to 5" transition, the airspeed at the surface of the 5" transition was 48 mph. (airspeed with a 4" pipe was off scale max of 67 mph)  With the same piping and with the dust separator installed, the speed was 45mph.  So this design only lost 3 mph.
Installed a .5micron wynn filter, put the motor on top of the collector, patched some leaks in the impeller housing, and put a foam insulation strip between the bottom bag and the housing.  With the dust separator installed, the speed improved to 51mph with the same piping as the previous test.   So getting rid of the 5" flex pipe and adding the extra area of the wynn filter gained about 6 mph as noted by others on this web site and elsewhere giving me a net gain with the dust collector of ~3 mph .
I used hvac 5" ducts for the main line and all drops from the ceiling are 4" pipe.  I made my own wyes since the commercial ones were expensive and the cheaper hvac ones had the wrong end crimped.  The longest run of 5" was about 16'.  For all 90 degree turns, I used 2 elbows at 45 to make more gradual turns.  After installing the pipe I tested the longest run of 5" pipe and the speed was only 38 mph.  Taping all the joints made a huge difference.  The speed was now 54mph.  A gain of ~3 mph changing the 10' - 4" flex pipe with the metal duct.
I allowed a cup of flour to be sucked into the inlet to the collector and ~ 2/3 of it ended up in the trash can.  There was some visible in the chamber and the edges of the trash can.  Some made it to the bag after the impeller.
Attached is a picture that better shows what I am describing.  I will reply to this and add other pictures it seems that I can only add one of this size at a time.

[nucww]

Picture of completed system.

[nucww]

Bird's eye view.

[nucww]

A correction to the velocity with the separator installed.  I was measuring the velocity of two different 5" pipes.  The separator pipe was  made to slide inside a standard 5" pipe so its area was less.  I can't measure it now but it could be a 1/4" OD difference which would reduce the relative flow by ~10%.  I am guessing it would make the 45mph to 40.5mph.

[retired2]

I think your "spiral" design is similar or the same as what is referred to as a "scroll" inlet.  There have been a number of discussions here on the subject.  I'm not sure if anyone has done a successful build though.  You might want to do a search on "scroll inlet".  I'm not sure what you will find, but there may ge something if interest.

[AndyF]

Nice!

that's a much cleaner build than what I cobbled together:
  http://www.jpthien.com/smf/index.php?topic=1085.0

[nucww]

AndyF,
Thanks for the compliment.  I remember looking at your post and was intrigued and was a reason I incorporated the spiral design.  I did not mean to imply that the significant differences that I used were my own ideas.  The only new idea is the flow redirection below the widemouth outlet.

Some general comments for those interested.
The Plexiglas at the top has shown an interesting behavior of the fine dust.  The fine dust collects on the Plexiglas while it is running and some dust does remain there.  It appears to be there because of the static caused by the moving dust.  It has a interesting spiral pattern.  When I touch the plexiglas with my whole hand, the dust moves away from my hand.  I wonder whether the circular section could be made of metal and a voltage applied to act like a electrostatic collector to enhance fine dust collection.  Once the flow is off, the voltage could be removed to drop the dust in the collection can.

Does this occur on the top of other designs made of MDF?

[bbain]

I'm curious what you are doing to raise /lower the can (or thee tophat itself) for emptying?  I am working on a system right now and want to do a similar wood frame to hold all of the components.

[nucww]

I simply use wedges at three locations under the can.