First Watercooled system build, few questions.

[QuietIce]

... and does the volume that the pump can circulate (lph) make a difference in temps?

Yes - and no.

Up to about 1 GPM the pump flow makes a big difference. Between 1-1.5 GPM there are differences but they get smaller as the flow gets larger. Once you're over ~1.5 GPM there is very little difference.

Note: Those GPMs are for a full loop, not the unrestricted pump flow that a quick spec sheet will give you ...

 

[SnoopDoug]

how would u not have a full loop?
so ur saying look for a 1 gpm pump then?

 

[BobbyBubblehead]

I can maybe source some facts and formulas on fluid dynamics... friend of mine was a civil engineer.

curious because I judge on fish pump experience (lots of) but to calculate things would be more enlightening I guess.

 

[QuietIce]

how would u not have a full loop?
so ur saying look for a 1 gpm pump then?

All pumps have an associated PQ curve with them and this curve is different for every pump. A quick sheet spec might say a pump is rated at 500 lph - but that's based on no load, no resistance. Since any loop has some resistance, then the amount the pump will move will be less than it's rating. As the resistance increases the amount of water moved will decrease:

In this chart the pressure is measured in mH20 (meters of water) or just m. At ~4.3 m the pump flow stops - that's the "head" or maximum "head pressure" of the pump. On the other end is the unrestricted flow rate, ~500 lph @ 0.0 m. Somewhere in between (we hope!) is where the loop resistance falls, and the lph will change accordingly. By adding up all the resistances in a full loop we can get close to where on the chart a given loop will fall.


That's why we usually suggest less restrictive blocks and shorter tubing runs - the less resistance, the more water is moved. Each block has a similar type curve showing how much resistance it has depending on the flow. (Notice this flow is in gpm instead of lph. 100 lph ~ 0.44 gpm or 1.0 gpm ~ 227 lph)

So how do you know if a pump is enough for your loop? While one block is easy to calculate (overlay the curves on one graph), mutliple blocks get complicated fast. There are ways to calculate it all out but the bottom line answer is simple, experience ...

 

[SnoopDoug]

sounds like the only way to find out is to just do 'er, dumb question if i dont have enough rad. then my temps will just be high right?

 

[BobbyBubblehead]

well it all happens in degrees in both senses. Wouldnt worry no one heres gonna plug you a race horse and it turn out to be a donkey.

 

[QuietIce]

sounds like the only way to find out is to just do 'er, dumb question if i dont have enough rad. then my temps will just be high right?

Yep, that's the bottom line ...