increasing flow efficiency through a manifold.

[ctenophors rule]

If flow into a manifold and out of a manifold is turbulent then attempting to create equal flow through each output opening via ball valves would be impossible. right or wrong?

If the flow exiting the manifold were laminar, or even transitional, flow would be much easier to equalise. correct?

considering these two statements, if valid, how could one calculate the neccesary diamater of manifold out put pipes to create laminar flow from a turbulent source?

if wrong, how would one go about creating equal (laminar) flow in a manifold when its feed is turbuent?

thanks

Tommy

 

[dots]

http://www.advancedaquarist.com/issues/jan2003/featurejp.htm

http://www.advancedaquarist.com/issues/sept2003/short.htm

Your understanding of "turbulent" and "laminar" flow is a little off by how it is effecting the system. Most of the time we are going to be dealing with turbulent flow.

Turbulent flow is defined by the Reynolds number above 4000.

What does this mean? A larger friction loss per foot of pipe that increases with a higher and higher Reynolds number.

To create a manifold with equal flows at each of the exits, all must have the same energy loss. So that Q1=Q2=Q3 (Q=Area*Velocity)

Which means, the loss from the point the flow is split to the farthest exit will be the greatest loss to friction. It should be no suprise that the one closest would be the least.

Ball valves artificially add more static head exponetially as they are closed. To compound this, it increases the TDH that the return pump sees on the system. Adding multiple ball valves and "playing submarine" with them, moves the duty points of the system and creates a poorly matched/ineffecient pump application.

What these ball valves are doing is like runners that are staged unequally on a track or a bracket race in drag racing. The faster car has to wait and let the slower car get down the track to in theory they end up at the finish line at the same time.

The exit closest would be closed the most, with each successive valve being closed less and less, to where the last one would be fully open.

Just be aware, in the end you may have plenty of "flow" but no velocity once it exits to create that "chaotic" flow in the display you are trying to create.

 

[teesquare]

The balancing of flow volume - vs- flow pressure has always been the fun/frustrating part.
And I agree with Doug. Once plumbing layout is achieved, and headloss calcs. are done - then look for pump curve which best fall in the range you are looking for.

A basic rule I like to use when at all possible is to upsize the pipe diameter, and then valve down near the exit point (usually near a bulkhead) in order to "tune" the effect of the flow I need to achieve in the aquarium.

Just one thing to remember - regardless of how well you configure the system when it is initally set up, the needs will change as corals grow, as they will deflect, and adsorb much more energy from the flow pattern than most consider when setting up a tank.
T

 

[ChadTheSpike]

"playing submarine"

Sorry to go OT, but I have to say, I get it and I love it.

 

[neoalchemist74]

Would'nt gate valves be better than ball valves in regards to loss of velocity

 

[dots]

Sorry to go OT, but I have to say, I get it and I love it.

This usually goes with it......

I just don't like how ball valves are liberally used and disregarded on how they effect the system curve when there are countless threads arguing about the efficiency of one pump versus another.

 

[teesquare]

Agreed...well sort of...
Used judiciously, and appropriately, valving is a good thing. It can make for a better system due to the feasability they bring. The ability to shut down one area, remove a pump, clean, etc. is invaluable in larger systems. I cannot imagine not having valves for these purposes. Also, as above to "trim" flows in a given use, - would not do it any other way - too many variables to base the life of the system ( which coral growth, re-arrangment of aquascaping and so on WILL change the impact of flow) on a one time set of calcs. Thes are not fixed, or static tanks as in an industrial or waste management scenario.

But the joke aspect of your picture post is well taken. I have seen many systems that had so many ill placed, and un-necessary valving on a lot of aquariums out there, without consideration of their impact on total flow .
T

 

[dots]

....its all in good fun/elaboration in the effort to help...

Gate valves are a more precise control for flow control and are the preferred method for doing so. Gate valves tend to have a higher "minor loss" than a ball valve, as seen in table 5, at wide open.

http://www.advancedaquarist.com/issues/jan2003/featurejp.htm

So with respect to the "minor loss" due to friction as the fluid passes through a fully open ball valve versus a gate valve, the ball valve has less frictional loss. This is pretty easily seen by looking through each....pretend your water, which one makes you move more to get through....gate valve



Historically, ball valves were only used for being "on" or "off". After a ton of searching, I found the friction factor (K)for a ball valve fully open (K=.05), 1/3 closed (K=5.5), and 2/3 closed (K=210).....and its an obvious exponetial increase.

For our applications, the flows we are dealing with a ball valve may be used but only then for slight adjustments of up to 10% or so...... We need to know what they really doing to the system duty points....which is what I soap box on commonly. (I find it so perplexing that pump selection commonly occurs before plumbing design, which is totally 100% backwards.)

In all instances, I would try to design the system without valving to have a rock solid duty point for a pump to be matched with.....and only use them if needed, as in the case for the OP's manifold....not to solve a poor pump selection.

 

[teesquare]

Well put Doug! Excellent explanation.
T

 

[ChadTheSpike]

This usually goes with it......

The memories that this brings back...

A "flow balance" is such a PIA...