Could someone please aid me in a flowrate discussion at another forum?

[Giblet Plus!]

Near the bottom:

http://genmay.net/showthread.php?s=&postid=6360626#post6360626

[9mmCensor]

If the block is .0000000000001 inch higher than the pump, you will not get any flow. ummm no, thats not how it works.

Yes. You said you understand that flowrate is constant. So how does changing the tubing change the flow rate?

The only way you can change the flow rate is by changing the waterblock, no it still doesn't. NM

no quite either.

Don't arrgue with those who refuse to listen to reason.

[CeleronDude]

Originally posted by 9mmCensor
Tool.

// Explain? Read my assumption that if the pump has almost no pressure. That means any head height will not give you any flow.


Super Tool.

Don't arrgue with those who refuse to listen to reason.

don't insult me without logic, please explain your point of view

wow, i can't believe you pulled me over here to argue with more people. One is enough.

[Cathar]

Let's make it simple shall we.

CD (CeleronDude) - do you agree that thinner tubing is more difficult to push water through than thicker tubing? You must, because such is evident all around us.

Secondly, waterpump pressure is not constant with respect to flow resistance (otherwise known as back-pressure). Pumps have what's known as PQ (pressure-flow) curves, which maps the flow rate that the pump can provide given a certain back-pressure.

For example (Eheim 1046-1250):

http://www.employees.org/~slf/images/eheimpq.jpg

Now if we're pushing say 5LPM (litres per minute) through 1/4" tubing, and then we put 1/2" tubing on there, the 1/2" tubing offers less flow resistance than 1/4" tubing (roughly 4x less).

Because the resistance is less, the pump will push more flow until the back-pressure provided by the tubing matches up with the pumping pressure that the pump can provide at the new/higher flow rate.

[Cathar]

I should add that flow resistance is generally proportional to the flow rate squared.

[CeleronDude]

Originally posted by Cathar
Let's make it simple shall we.

CD (CeleronDude) - do you agree that thinner tubing is more difficult to push water through than thicker tubing? You must, because such is evident all around us.

Secondly, waterpump pressure is not constant with respect to flow resistance (otherwise known as back-pressure). Pumps have what's known as PQ (pressure-flow) curves, which maps the flow rate that the pump can provide given a certain back-pressure.

For example (Eheim 1046-1250):

http://www.employees.org/~slf/images/eheimpq.jpg

Now if we're pushing say 5LPM (litres per minute) through 1/4" tubing, and then we put 1/2" tubing on there, the 1/2" tubing offers less flow resistance than 1/4" tubing (roughly 4x less).

Because the resistance is less, the pump will push more flow until the back-pressure provided by the tubing matches up with the pumping pressure that the pump can provide at the new/higher flow rate.

Ok, i guess by thin tubings you mean larger diameter tubings. This is true.

Unless your pump is really weak, tubing size doesn't matter.

But like my first post on the page over genmay says, if your pump has enough pressure such that backpressure will not hinder the performance of the pump, then tubing size makes no difference. That is why we can't just use 1/16" tubing because the back pressure would be too great. Hover, if the pump is strong enough that it can overcome the backpressure and still remains relatively stable in terms of rated output, then we can still use 1/16" tubing.

If you read my posts, i've pretty much assumed constant pressure from the pump. Obviously that isn't true because this is the real world.

[Cathar]

Originally posted by CeleronDude

Ok, i guess by thin tubings you mean larger diameter tubings. This is true.


Yes. That's what I meant. I was just repeating the terminology that Giblet used. Thin = small diameter. Thick = larger diameter.

Originally posted by CeleronDude

But like my first post on the page over genmay says, if your pump has enough such that backpressure will not hinder the performance of the pump, then tubing size makes no difference. That is why we can't just use 1/16" tubing because the back pressure would be too great. Hover, if the pump is strong enough that it can overcome the backpressure and still remains relatively stable in terms of rated output, then we can still use 1/16" tubing.

Well here's where we need to land back into the realm of reality. For your statement to make sense, you need to provide evidence that such a pump is in fact available and in common use.

There are pumps that will do what you say. They are known as positive displacement pumps whereby they will just keep on increasing the pressure (to quite fantastic levels - as in many thousands of PSI) in order to sustain a constant flow rate against increased back pressure.

Such pumps are commonly found with extremely large and strong motors attached (rated in kilowatts, not handfuls of watts that us computer coolers use), and really it must be said, given the choice between using a mega-powerful pump to sustain flow through small-ID tubing, as opposed to just using a cheap/weak pump to give the same flow-rate through large-ID tubing, one would clearly choose the latter, as beefing up the pump just to overcome the flow restriction of the tubing is just an exercise in futility.

[Giblet Plus!]

Thanks cathar. :)

[eobard]

Originally posted by CeleronDude

wow, i can't believe you pulled me over here to argue with more people. One is enough.
Me either. Arguments are best kept for places that aren't here. We had a place for arguments in these forums, it was called "Debates" and it caused more problems than it solved. Now I'm not saying people can't have differing views, but we do not need this place to turn into one great big s[H]outing area.

Originally posted by Giblet Plus!
Go argue at procooling.com or the overclockers.com forums.
Please don't make that recommendation again. :mad:

btw: for those who want to continue the "argument", take it back to General [M]ayhem. *click*