5", Rectangular Inlet, Bellmouth Outlet with Air Straightener, Top Hat Separator

[Geezer]

Sometime earlier I posted this paragraph from a Cincinnati Fan Engineering manual regarding duct inlet spin.

Duct Inlet Spin
"A major cause of reduced fan performance is an inlet duct connection that produces a spin or pre-rotation of the air entering the fan inlet.  Inlet spin in the same direction of the fan wheel will reduce air volume and pressure ratings.  Inlet spin in the opposite direction of the fan rotation will substantially increase the motor horsepower requirements.  An ideal inlet condition is one which allows the air to enter the fan axially and evenly without spin in either direction."

Interesting to see that air rotation in any direction is detrimental to performance.

Also interesting to note entrance design losses (attached).

Appreciate all the effort you've put into testing and reporting back your findings.

[dabullseye]

just wondering if it would be better to put the straws rt on the DC since mine is mounted up on a platform and offset from the trash can

[retired2]

just wondering if it would be better to put the straws rt on the DC since mine is mounted up on a platform and offset from the trash can

I doubt that it would make much, if any, difference.  It should be beneficial either place.  My straws are 8" long, and that was totally arbitrary, so I have no idea how long is long enough, or how short is too short.

Regards,
Retired2

p.s.  My tubes were 1-1/2" diameter shipping tubes for some Krell aluminium tracks I purchased.  I thought it would be easy to buy more, but I'm starting to think sourcing this thin wall PETG tubing is going to be a major problem.  I can't find any suppliers unless I want to purchase a huge quantity.  The only tubing I can find is heavy walled stuff, and you don't want to use that because you will loose too much area and probably generate some turbulance which is exactly what you are trying to eliminate. 

[dabullseye]

check out fluorescent bulb safety cover tubes

[retired2]

check out fluorescent bulb safety cover tubes

Where?  Did a quick check of Amazon, Home Depot, Lowes, and Ace Hardware.  No luck.

[phil (admin)]

check out fluorescent bulb safety cover tubes

Where?  Did a quick check of Amazon, Home Depot, Lowes, and Ace Hardware.  No luck.

I've seen them at Lowes and HD.  They're 4 or 8' long and T-12 tubes are 1-1/4", so these might be just the ticket.  You might not find them online, you might have to travel to a store.

[retired2]

check out fluorescent bulb safety cover tubes

Where?  Did a quick check of Amazon, Home Depot, Lowes, and Ace Hardware.  No luck.

I've seen them at Lowes and HD.  They're 4 or 8' long and T-12 tubes are 1-1/4", so these might be just the ticket.  You might not find them online, you might have to travel to a store.

Thanks Phil.  Thus far, all my searching has been on-line, so I'll check out the local stores.  I did find this on-line source, but they don't have 1-1/2" diameter.  The reason I like the 1-1/2" is it works out nearly perfectly for stuffing a 5" pipe. 
 
http://www.tapplastics.com/shop/product.php?pid=274&

I tried laying out other diameter tubes in a 5" circle using paper templates, but that doesn't work because in reality the tubes get squeezed just a little into a slight elliptical shape.  If they are too big, they flatten, too small and they won't stay put, and it is hard to glue the contact lines.  So, the only way to really know how a given size will work is buy enough to try it.  In fact, I've been thinking that what might work best is a mix of more than one size.

[Rick T]

was thinking about golf club tubes and they are 1 1/2" dia and pretty robust. Here's an example. http://www.golfsmith.com/product/30032085/ztech-golf-bag-tubes

[retired2]

was thinking about golf club tubes and they are 1 1/2" dia and pretty robust. Here's an example. http://www.golfsmith.com/product/30032085/ztech-golf-bag-tubes

Since I'm a golfer, I thought about those too.  Just haven't had a chance to stop into our Golf Galaxy to check them out.  They definately are a different material, not that that matters as long as the wall thickness isn't too heavy and as long as they respond to some adhesive, preferably crazy glue.   That makes it very easy to glue the stack together. 

When I glued mine up, all the tubes were in contact with one another because they were squeezed snugly into a 5" pipe.  Then I just held the pipe so it was tilted slightly below horizontal.  Then I put a couple drops of crazy glue on each contact line.  The crazy glue would run all the way to the other end where eventually it evaporates and the tubes are welded together.  It would be nice if that worked with the golf club tubes.

[Rick T]

Golf is far to frustrating for me so it's nice to know there may be some good that can come from it. As far as gluing them together, wonder if you could use spray foam? Spray a quick shot into voids between if that's what you are thinking about. Do that at both ends since it doesn't matter what the tubes do in the mid-section. That foam is a pretty powerful adhesive.

[phil (admin)]

In fact, I've been thinking that what might work best is a mix of more than one size.

I was just at Menards where they have two different sizes, one for T-8, and another for T-12.  I didn't check the diameters, but will next time I'm there.

[DarthVader]

so according to the chart, my unflange pipe is restricting the airflow by about 90%? so just by adding a bellmouth, i can increase airflow quite a bit(hopefully 90%)? that would be awesome but seems hard to believe.

where can i get a decent bellmouth in 6"? ive only found penn states(psi), but the radius stops right at the top of where it should transition into the actual pipe. thanks in advance to all.

[retired2]

Golf is far to frustrating for me so it's nice to know there may be some good that can come from it. As far as gluing them together, wonder if you could use spray foam? Spray a quick shot into voids between if that's what you are thinking about. Do that at both ends since it doesn't matter what the tubes do in the mid-section. That foam is a pretty powerful adhesive.

I'm not familiar with this adhesive, but if it fills any air slots, even the small ones between the tubes, I wouldn't use it.  You don't want to give up anymore of the free area than is lost by the tube wall thickness.

[retired2]

so according to the chart, my unflange pipe is restricting the airflow by about 90%? so just by adding a bellmouth, i can increase airflow quite a bit(hopefully 90%)? that would be awesome but seems hard to believe.

where can i get a decent bellmouth in 6"? ive only found penn states(psi), but the radius stops right at the top of where it should transition into the actual pipe. thanks in advance to all.

No, no, no, you are not restricting airflow by 90%  You are losing what is called velocity pressure.  Velocity pressure is the amount of pressure required to get air moving to a given velocity.  As you lose velocity pressure, some static pressure is added.  That static pressure represents the loss.  Now don't ask me how to quantify that because I don't have that level of understanding.  I can only refer you to the two different sets of test data that I've posted in this thread, and you can see there clearly is a tangible benefit.  Since my second set of data included anemometer readings you can see the benefit in FPM or CFM.  I would also like to refer you to another thread that I started that explains things a little better.  That thread is titled "Bell mouth outlet pipe?", and it was started on August 4th.

I don't think PSI's bell mouth is any different than mine.  They are all very short.  You need to attach a stub pipe to them.  The thread  I mentioned in the previous paragraph has photos and dimensions of my bell mouth before and after I attached the pipe.   

[dabullseye]

i would really talk to somebody at penn state and have them give you the real size of the bellmouth, they list em as 6" but they are more like 5.5