I wrote the following to try and help with some of the theoretical considerations going into pipe flow and assist in loop configs here for people. I bow down to B-negatives knowledge of realworld materials and the plumbing practice (I claim no knowledge in this area and he is awesome!) What I have written more is to address theory and maybe clear up reasoning behind a decision you want to make about a loop, how many bends, sections, etc.
1. Ocean engineer from #1 program in the United states (top 10 engineering school for all other programs)
2. I've had 4 classes directly addressing closed and open fluid flow, and all other classes involved fluids in some way (3.45/4 gpa)
3. Will be working for EMAS AMC as Subsea pipeline systems engineer starting in June 2013
I tell you this not to brag or any such thing, simply to validate the things I have written were done by someone not completely speaking from thin air and no background
Hey guys love the thread but just some insights from an ocean engineer....
1. pipe bends will add to pipe restriction (but not by much). The entrance and exit points for pipe sections add the most restrictions for flow. The math is done with coeffieceints and a bend gets around .15 while and entrance and exit is around a 1 in restriction coefficients math when added up to make pressure calculations. THEREFORE when piping keep the sections/segments (which transaltes to exits/entrances) of pipe to a minimum but realistically make as many bends as you need it won't matter unless changing direction 90 degrees or more, or having an obscene amount of bends. almost 7 bends = one exit/entrance point
2. placing double pipes (tandem) will not offer any increased amount of fluid flow if you use those "y" fittings. the reason for this being that the flow rate Q will be choked down at the consolidation point which is those fittings. if you can have two pressured tubes run from something like say a res to another res then the flow rate will be more or dual pumps into one y fitting, but if you have to consolidate down to one tube or fitting at some point then NO your flow rate or "amount of fluid moved per unit of time" in something like liters per minute or gpm will not be increased at all beyond the flow rate through the single tubed sections.
SO any one who wants to do this for aesthetics, rock on it will look sick!
BUT you will get ZERO performance upgrade or higher flow to components because obviously to flow through a pc block there's only one channel right? gpu blocks are the same, so unless its a multiple input/ output block with multiple channels then you will see no gains and will see resistance (pump head) increase due to multiple restrictions introduced into the loop
the only way this will help is because there is more fluid in the system, which will give you more thermal overhead initially but once all the fluid is heated up to the same levels it wont matter much and the difference might become negligible (this is why WC has not evolved to include massive reservoirs, once the system is at a thermal equilibrium it doesn't matter how much fluid is in it, its closed, the only thing taking away heat is the dissipation in the radiators)
in addition when thinking about larger diameter tubes anticipating more flow. The flow you will get in your loop will never exceed the pumps movement amounts (which i figure everyone knows) but to clarify larger od will move fluid slower than smaller od in relation to the od for the in/out at the pumps.
ie: if the pump has 10 gpm (made up number) with od out of 1/2" then you increase the od of the pipe in the loop to 3/4" the flow rate at any point in the 3/4 tube will not be the same speed as leaving the 10 gpm pump and for every point that the flow profile diameter (pipe diameter gets larger or smaller it will cause restriction to flow (no matter bigger or smaller) think of it like getting smaller the pump must work harder to move same amount of water through the pipe and larger causes the pipe to require more fluid volume per inch to fill and causes more work for the pump at the interface change.
let me be clear IF the pump is rated at 10 gpm, then it will deliver 10 gpm....but it is only moving that parcel of water and nothing more or less if set at that speed. all you are doing with larger od is keeping the speed at a given point in a loop slower because the fluid parcel is spread over a larger diameter as it moves (per unit force being put out by the pump its only going to move so much volume so far and larger od makes the volume per inch larger and more energy needed to move the same distance hence slower.... smaller od is like a rocket engine it will move faster through a pipe due to the same principle in reverse.
roughness factor of copper vs. acrylic vs. stainless etc. should not really matter for loops this small in a pc to where it really would govern the pipe choice (most pc WC pumps are overkill and won't be affected by a slightly more ore less rough pipe material
AND difference between smaller and larger diameter pipes why or why not? if you have a larger spread of a loop where you need speed to keep momentum to make it to everything and lots of restrictions id say go smaller.....if you have a really heavy duty loop (lots of things needing heat disipation) then I'd say go for more OD because the slower moving loop will absorb more heat as it moves and take it away from the components (this should be done withing reason though, too slow is obviously bad as it wont dissipate fast enough.
WC is 100% about a balance between contact surface area of water per a unit of time ( how long it is in contact) which is directly related to the speed of a loop and amount of water moved. So a super fast loop will not do much for you, or a super slow loop will not do well either. variable pumps will help with this balance but another way of slowing or speeding a loop involves the choice of OD of your pipes.
VERTICAL distances also matter, I won't go into it but hydro-statically (weight of water) this translates directly into pump head which is what will affect your loop the most as it is what the pump is fighting to overcome.
Is this important at all? depends
the small variations in OD relatively (3/8-3/4") and small variations of loop length ( 6ft-10ft) these concepts obviously apply and they are scalable (they work the same at massive pipe levels or small. but given the over engineering that goes into enthusiast WC pumps most use on OCN....it may or may not be of interest to make all these considerations. I'd say realistically it may only be the difference between 3-5C or more Conservatively 2-3C if you make the right optimizations. But for anyone looking to push machines to the absolute limits or find that balance of fan noise they making these choices could make the difference for you...
I wrote this to try and HELP! not to hurt any ones feelings or degrade your decisions! I think everyone's work here is great and I hope to join the club sometime this year when i get a chance and the time. Knowledge is power so I'm just trying to spread the love a bit and see if it helps anyone here.
If you read the whole thing then cheers! and hope you found it worth the read and relevant Edited by oats2012 - 3/31/13 at 2:15am