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Old 01/10/2008, 06:56 PM   #26
NanoReefWanabe
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i am curious why they say that valving the pump will save on hydro though...i thought increasing head pressure would increase power consumption which in this case would be wasted as heat...i could see if you actually changed the power to the pump to slow it down then i could see how that would reduce flow and save power...


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Old 01/10/2008, 06:57 PM   #27
kgross
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The weight of the water does not effect head pressure at all. The pipes and pump hold up the actual wight of the water. The only thing about the weight that effects the pump flow is the PSI at the pump output or vertical head.

The sudden increase in size or decrease in size does effect flow (normally not a very noticeable amount. The reason it does effect the flow is that the water has inertia and any change in the pipe causes the water to change direction or velocity, so it has to overcome the inertia. Just coupling 2 pipes together effects the flow rate via the same means that going to a larger pipe effects the flow.

Nano reef wanabe, before you say don't need to know any engineering you need to try the experiment out. You can blow the water up the same height, no matter what diameter the pipe is (unless you consider capillary movement ). Get a few feet of clear hose so you can see what you are doing. Put the hose in a U with the U down and see how far you can raise the water level in one side of the U. Try this with lots of different sizes of tube. You will find that the size of the tube does not make any difference.

Kim


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Old 01/10/2008, 07:02 PM   #28
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Nano, this is why you need to understand how stuff works before you post about how it works. The pump "does work" when it moves water. The more water it moves the work is done. The more work that is done, the more power is needed. The pump is actually creating the same " pressure" no matter how much water moves, the amount of pressure that the pump creates determines how much water is moved. If there is lots of static head pressure, the pump has less pressure to overcome the dynamic head pressure (friction loss) to move water. So when you reduce the friction, there is more pressue left to allow a higher velocity of water to use up the pressure that is left.

Kim


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Old 01/10/2008, 07:45 PM   #29
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Quote:
Originally posted by NanoReefWanabe
3000GPH would be about 10X turnover for his setup...not including skimmer volume sump volume refuge volume...i dont think that is too far out of the question...most i think aim for about 5 times turn over through their sumps...i bet he would be pretty close to that after everything is added up...
I run a manifold around the top of my tank with 9 outlets on it.. so you divy up 3000 x 9 outlets gets me about 300 gph out of each . see pic in the link below.
http://smg.photobucket.com/albums/v6...ifold1inch.jpg

the picture is of an old manifold I made up first .. but you get the idea. bumped the diameter of it up to 1.5" piping


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Old 01/10/2008, 07:50 PM   #30
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Quote:
Originally posted by not_sponsored
If you're pumping 1200 gph in the pipe, the difference between a 1.5" pipe and a 3" pipe is 2.5 feet of head per 100 feet of pipe. In this case you'll be working with less than 10 feet of pipe or .25 feet less head by switching from a 1.5" pipe to a 3" pipe, TWICE THE DIAMETER.

http://www.engineeringtoolbox.com/pr...pes-d_404.html

On the other hand, lets say we have 5 90 degree fittings, for 1.5" pipe that would add 4 feet of head for every 90, or 20 feet of head.

Using 3" pipe we would add 7.9 feet of head for every 90 or 39.5 feet of head.
http://www.engineeringtoolbox.com/pv...ngs-d_801.html

This is a difference of 19.5 feet for the different sized pipes, for MINOR head loss. Compare this with the .25 feet of head loss caused by decreasing the pipe size in MAJOR head loss.
Sorry to say but you are rading the equivalent lenght of fittings table wrong.
The table of equivalents will give you the equivalent in lenght of stright pipe not of feet of head loss.

A 3" 90* elbow is equivalent to 7.9 feet of stright 3"pipe and a 2" 90* elbow is equivalent to 5.7 feet of stright 2" pipe, a 11/2" 90* elbow is equivalent to 4 feet of stright 11/2" and so on.

Eventhough the equivalent straight pipe is higher the pressure loss is lower.
At a flow of 1200 gph .
7.9 feet of 3" pipe will have 0.0079 ft of head pressure drp
5.7 feet of 2" pipe will have 0.0456 ft of head pressure drop
4 feet of 11/2" pipe will have 0.104 ft of head pressure drop.

So in other words a 90* 11/2" elbow will have a head pressure loss that is 2.3 times larger than a 2" elbow.

If you drop the diameter to 1" that difference comes to that a 1" 90* elbow (2.5 ft equivalent) will have a pressure drop of 0.53 ft of head which is 11.6 times higher than the pressure drop across a 2" elbow eventhough its equivalent lenght is only 2.5 ft compared to the 5.7 feet of 2" elbow.


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Old 01/10/2008, 07:53 PM   #31
RonD
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Quote:
Originally posted by kgross
Is this pump going to be your return pump or a closed loop pump? If it is return why are you trying to do 3000 + gph through your sump?
its the Return.. and its a busy sump.. supplys my frag tank, algae tank and skimmer. it works lol


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Old 01/10/2008, 08:03 PM   #32
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That is going to be a busy sump. Personally I would suggest slowing down your overflow and using that big pump as a closed loop. System will be a lot quiter and you will get much better surface skimming going into the skimmer.

Kim


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Old 01/10/2008, 08:37 PM   #33
jdieck
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Quote:
Originally posted by NanoReefWanabe
i am curious why they say that valving the pump will save on hydro though...i thought increasing head pressure would increase power consumption which in this case would be wasted as heat...i could see if you actually changed the power to the pump to slow it down then i could see how that would reduce flow and save power...
The change in power consumption on a centrifugal pump is proportional to the change in flow and also to the change in head.

The actual formula is:
BHP = (Q x H x SG)/(3960 x % EF)
where
BHP = Break Horse Power
Q = Flow in gal per minute
H = Pressure head in feet
SG = Specific Gravity (1.0264 for salt water at 35 PPT salinity)
3960 is conversion factor foot-pounds for horsepower and weight of 1 gal of water (33,000 / 8.33)
% Eff is the efficiency of the pump

So as you can see for a given required flow increasing the head will require an increase in power and for a given head increasing the flow will require an increase in power.
When you install a valve to restrict the output of a pump you do so by increasing the head so to keep the same flow more power will be required but because you do not change the motor size the flow will drop and the drop in flow makes the power drop. It just happens that the drop in flow reduces the power more than the increase of head increases it so the net effect is an overall drop in power.

Take a look at this chart.
In indicates a typical performance curve for a centrifugal pump and charts the head vs flow (which is the one we usually get from manufacturers); the BHP vs flow (That we should get from manufacturers but our aquarium pump manufacturers do not usually provide it, I think they are afraid we find out about power consumption claims being manipulated) and finally efficiency vs flow.



Note that all centrifugal pumps are usually designed to operate optimally at certain point where a combination of flow and head will intercept with the maximum efficiency; either before or beyond that point the efficiency will drop but power will drop for before the point and will increase beyond that point.

So note that in this example a 10% increase in head (from 100 to 110%) will drop the flow from 100 to about 65%, the power from 100 to 80% and the efficiency also from 100 to 80% of the maximum efficiency.

On the other hand, an increase in flow from 100 to 120% by reducing the head from 100 to 78% will increase power consumption by about 8% (100 to 108%) but efficiency will drop from 100 to about 88%.

Hope this explanation helps in better understanding the behaviour of centrifugal pumps.


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Old 01/10/2008, 08:53 PM   #34
NanoReefWanabe
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and all of the above posts are exactly what i like to see...especially at this point in the day where i feel that i havent learned anything new...LOL thanx for the straightening guys...i always appreciate learning new stuff

BTW...i wasnt saying that is how things are, but rather was my understanding of things as i saw them....and once again appreciate my ignorance being not only highlighted...but rather...being educated...


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