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View Full Version : Flow restriction question/Fluid Dynamics



sconisbee
02-23-2008, 05:41 PM
I have a part im intending on making (for personal non business use before i get flamed), Basicly it has a hose barb one end, and a Hozelock style quickrelease the other end, has to be stainless and will be from solid bar, but thats not the problem, so calling all math/fluid dynamics gurus....

Say i have water at around 20*c and at a supply pressure of 50psi and i want to restrict its flow to around about 8 liters per minute can be less, but certainly no more than 9 liters per minute..... what size hole/bore/orrafice would i be looking at in this part? or alternativly anyone know a program that handles that kind of problem?

because its in stainless i'm planning on drilling through the part to within 5mm of the other end then that only leaves me with a 5mm depth to drill the restriction orrafice through.

Drawing to follow if necisarry.

barts
02-23-2008, 06:23 PM
http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm#calc

says .3 cm orifice in a 1 cm bore will do what you want if I got it right....

Clear cookies for the site if they want you to register, and try again :-).

These sorts of things are very empirical; I'd certainly start on the small
side and sneak up to it, as flow rates are dependent on a lot of small
details such as sharpness of hole edges, etc.

- Bart

aostling
02-23-2008, 06:30 PM
There is an orifice plate calculator at http://www.flowmeterdirectory.com/flowmeter_orifice_calc.html.

Using some English units -- assuming a 1" diameter tube, water density (62.4 lbm/ft3), water kinematic viscosity at 20˚C (0.0378 ft2/hr), deltaP (50 psi), the calculator shows that an orifice of 0.125" diameter will give flow of .456 m3/hour, which is 7.7 liter/min.

PaulF
02-23-2008, 06:36 PM
SB,
Why not use a metering valve in line than you can adjust to what ever flow from 0-Max.
PaulF

sconisbee
02-23-2008, 07:16 PM
now thats why i love this place, i spent hours looking for stuff earlier, not sure how i missed the efunda site tho, thankyou! something to play with tommorow.

Paulf, thats kinda how im doing it at the moment however wheres its going to be installed theres not going to be much room for a valve, other than the main on/off control valve. Its part of a filtering system feeding a couple of tanks that contain some very very rare fish, and the carbon filters have a flow rate max on them of 9 liters a minute, thus somewhere around 7 or 8 liters a minute gives me room for any water pressure fluxuation.

aostling: now thats a sweet page, gives me a chance to learn (or try at least) the math behind it too! thankyou.

Thanks all for the help!

andy_b
02-23-2008, 11:05 PM
Its part of a filtering system feeding a couple of tanks that contain some very very rare fish

are you allowed to say what kind of fish? since i was about 7 years old i've had an aquarium of one type or another around (sometimes several). i understand if you don't want to say for various reasons.

andy b.

sconisbee
02-24-2008, 06:29 AM
are you allowed to say what kind of fish? since i was about 7 years old i've had an aquarium of one type or another around (sometimes several). i understand if you don't want to say for various reasons.
andy b.

oh i dont mind at all, I've got one of the first ever tank bred Synodontis Granulosus, and a male and female Synodontis Ornatipinnis which are the real rare ones, there are others but im too lazy to look up spelling and they arn't as rare:D
oh yea got a bunch of C. wietzmani's too in a different tank. I did have an absolutly perfect specimin of L25/Scarlet Plec but i've had a run of bad luck and one of the others for no reason at all decided to kill it last week (which is wierd cause its been in the same tank with the same fish for over 2 years now):mad:
I currently stand at around 1100 liters of tank space, and water changes with buckets is getting on my nerves!:D :rolleyes:

John Stevenson
02-24-2008, 06:45 AM
http://www.planetcatfish.com/images/full/mochokidae/synodontis/ornatipinnis/1.jpghttp://www.planetcatfish.com/images/full/mochokidae/synodontis/ornatipinnis/1.jpghttp://homepage.ntlworld.com/stevenson.engineers/lsteve/files/1.jpg

Ugly little bastard isn't it ?


.

sconisbee
02-24-2008, 08:54 AM
LMAO! whats that old saying...Beauty is in the eye of the beholder or somethin like that!:D They dont look like that when older but similar.

Besides they say pets take after thier owners, and im ugly so my pets are gunna be too! LMAO:D

HTRN
02-24-2008, 02:49 PM
I currently stand at around 1100 liters of tank space, and water changes with buckets is getting on my nerves!:D :rolleyes:

Oh man, does that bring back memories.

At our peak, between my brother and me, we had 7 tanks running with fish in them at the same time. From a 125 holding some big Pacu's and a 2 foot snakehead, to a 10 gallon tank with tetras in it.

It got to be a genuine LOATHING to do water changes every week.

I still have the stand from the 125 in my basement. Mebbe I should get a new tank..:)


HTRN

sconisbee
02-24-2008, 04:47 PM
I still have the stand from the 125 in my basement. Mebbe I should get a new tank..:)
HTRN

Yes, yes you should!:D just be careful of catching the dreaded MTS and ending up with a house full of water.:rolleyes:

I run 6 tanks currently, the largest being 6 foot by 2 by 2. the flaming oscars are gunna eat me out of house and home soon! they are like pigs with fins!:rolleyes:

HTRN
02-24-2008, 05:04 PM
My "Multiple tank syndrome" is currently in remission.:D

The tank was actually my brothers, but my mom wanted the damn thing out of her house - so it was sold.. The guys who bought it though, didn't want the stand.

I imediately chimed in "Hey, don't throw it out! That would make a good work bench stand!"..:D

So it sits, waiting for another tank(This time, it's going to be a 150)..

Lately though, I've thought about building Acrylic tanks (http://www.cichlid-forum.com/articles/diy_acrylic_aquarium.php) - it's seems easy enough - build some holding fixtures and it becomes like glueing plywood.

Next time I'm up in Little falls, I'll have to check Emco's (http://www.emcoplastics.com/) scrap bin and see what they have cheap.:)


HTRN

oldtiffie
02-24-2008, 06:18 PM
There is an orifice plate calculator at http://www.flowmeterdirectory.com/flowmeter_orifice_calc.html.

Using some English units -- assuming a 1" diameter tube, water density (62.4 lbm/ft3), water kinematic viscosity at 20˚C (0.0378 ft2/hr), deltaP (50 psi), the calculator shows that an orifice of 0.125" diameter will give flow of .456 m3/hour, which is 7.7 liter/min.

Good post Allan and others.

We used to use restrictive/"rated" orifices in/for steam and hydraulics.

There were essentially just a disc with a hole in them that were placed in something like a flanged joint. But the shape of the hole had quite an effect as well as the diameter as I recall (it was a long time ago).

The pipe/tube was as large as was practical to reduce fluid velocity and friction and surface turbulence with the resultant energy losses.

The sizes of the discs were obtained either mathematically or empirically (or from experience), or from tables - and "guess-work" too. The losses varied as I recall as the square (cube??) of the increase in velocity - so the savings were very considerable in a marine environment.

A "tap" or "regulator" or "valve" if not fully open or closed will or may cause a lot of fluid resistance, turbulence and energy loss as evidenced by the high pitched "squealing". It is less so if a restrictive or "rated" disc or orifice is used.

For the skeptics - as proof - just try blowing slowly down a soft drink straw - easy ain't it? Now increase how hard you blow - the resistance really ramps up to the point where your ears will "pop" with no increase in fluid flow.

Even a 2" square security fence mesh will become almost "solid" in its resistance to wind flow rate if the wind speed is high enough - and so the fence becomes a sail or a wall and gets blown over.

This is a bit outside the topic of fluid mechanics and physics etc. but get a Structural Engineer to take you through your country's "Wind Loading Code" - especially the "gust" component. Water, fluids and gasses have tremendous energy at times that is often hidden (latent) or ignored - at your peril.

I will be interested in how the end result relates to the calculations in this thread.

sconisbee
02-24-2008, 07:27 PM
My "Multiple tank syndrome" is currently in remission.:D
HTRN

It wont last! as you know its just as bad as New tool syndrome:p

Dont even mention acyrilic tanks!!! i'm soooooooooo tempted to build a real big one, some where in the region of 1200 liters on its own (the 6foot is around 180US gal i think/700ish liters).
i have grand plans that will get me into alot of trouble if im not carefull!:D

Thanks tiffie, ill be sure to post the results of the flow restricter when i get my finger out and make it:rolleyes: Had a lazy day today and got a large backlog of work for the next few days so like the rotary broach its on the back burner