[Fatalmistake]

guy i hope you can put this question to rest for me. i heard (and i cant remember where or when but it has been a while) that having a water pump that is two fast is just as bad as having a water pump that is two slow. something about it pumping the water to fast to be cooled or it not being on the water clock long enough to cool the PC. any idea if im just dumb or is this true?

 

[Chunky_Chimp]

Nope, it's not true. Water cannot be pumped so quickly that it does not transfer heat.

 

[Rian]

Quote:

Originally Posted by Chunky_Chimp Nope, it's not true. Water cannot be pumped so quickly that it does not transfer heat.

my pump is quite fast, when it comes out the rad and into the res you can hear and see the water hitting the glass, not sure if this is mormal but its coolling fine and id say its going pretty fast.

 

[koooowweeee]

if its fast it going to get back to the rad quicker and keep on doing so. quicker the better

 

[Chunky_Chimp]

Quote:

Originally Posted by Rian my pump is quite fast, when it comes out the rad and into the res you can hear and see the water hitting the glass, not sure if this is mormal but its coolling fine and id say its going pretty fast.

Right. I'll elaborate just for kicks, though;

Assuming you've filled and bled air from the loop, the water running through the tubes is a solid stream of thermally conductive liquid. However fast it runs, it will transfer heat to the radiator (for the fans to blow away) just as well slow as it would be fast; it all depends on restriction in the blocks. If it flows too slowly through the blocks, naturally this isn't a good thing. But moving too quickly isn't an issue, because it's the same solid stream; temps will not change above a certain flowrate (and this differs between each config so I can't tell you what that is).

An analogy you could use is a computer's CD player... you can spin the CD as fast as you want, but it won't play the music any faster unless you speed it up with software. Spin it too slow, though, and it won't play well if at all. This is because the laser knows how to adjust for the rotation speed; of course this is different as the flowrate in a water loop doesn't need to adjust according to temperature (although it is possible). Below a certain point, though, the laser is unable to adjust and playback suffers and eventually stops. Same deal with a water loop; too slow and temps suffer. But too fast and you won't actually notice how fast it's going because it won't be more efficient. This is why head matters more when selecting a pump for restrictive loops; it needs to get the water through the block(s) and radiator(s), and as long as it does that efficiently, the actual flowrate becomes a non-issue.

There's a better way to put this, but it's quite late and I'm about to fall asleep where I sit; I'm sure someone can detail it better.

 

[voigts]

With the types of pumps that we would use in PC watercooling, having too high of a flowrate is usually not an issue. One pump of the DDC/MCP kind are not going to run into any kind of issues.

It is possible however to have multiple pump setups that run into issues. Flowrates above 1.5gpm offer very little performance increases. What can happen when using multiple pumps is that the increased heat dump counters the only slightly better cooling at very high flow rates which can result in a slight drop in performance (think around 3gpm +). I have seen this happen with people that have tried to use 2 x MCP355 pumps in a very low restriction system, or 3 x MCP355 pumps in a higher restriction system. They could remove one pump and their temps would actually improve a bit. Briefly, this is because there is only a marginal increase above 1.5gpm, and the effective heat dump countered the only slighter temp decrease that a really high flow rate offers.

 

[tilldeathdoesmein]

Heat dumps this, and flow rates that.... No offense intended, but your all complicating what could be a simple matter OR over simplifying a SERIOUSLY complex equation.

You can either set up a loop with good parts and have confidence in your loop, or you can open up a liquid flow CAD program and spend countless hours calculating drag, resistance, force, flow rate, heat exchange, thermal conductance, thermal insulation, and so on and so on and so on.

Multiple (identical) pumps will increase head pressure (only calculable with a quadratic equation, it's NOT a linear formula), very minutely increase flow rate, increase thermal seepage (from the additional pump) which again is only minute, and finally increase your total power consumption.

 

[Chunky_Chimp]

I see what you're getting at, but this is a somewhat old topic and I think the point was already made. Good for explaining it better, though, like I'd said I was sure it could be.

 

[tilldeathdoesmein]

I was not attempting to correct you or anyone aside from Voigts, multiple pumps ARE a viable solution for those who 1.have multiple reservoirs 2.have high head-travel lines 3.decided to cheap out with low head pressure pumps.

 

[Chunky_Chimp]

Yeah, I know. It's a good point to make when that XSPC X2O 750 has become so popular when its pump only has a third of the head pressure of a D5.

 

[tilldeathdoesmein]

Precisely.

 

[ira-k]

Pump heat dump is your main concern, after a point any extra flow is negated by the pump heat dump. Most newer blocks and rad's really don't need high flow to perform well.

I try to stay under 50W or so pump dump.

How much pump is enough? How much is too much?

 

[Lievyon]

First off don't take my word for it go here and look at some actual data:

http://skinneelabs.com/i7-blocks-2.html

Now, while to high a flow rate isn't as bad as too low there still is a point where more is actually worse. The reason for this is because all water blocks attempt to create a certain amount of turbulence inside them. This increase the cooling performace. If flow rate is too high, it actually reduces the amount of turbulence created and lowers cooling.

Skinnee has stated this quite a bit, it looks like about 1.5 gallons/min is optimal with a good margin for error.

I think voigts said it best though. With a 1 pump loop with a few water blocks most people are going to be in the ball park. It's the very restrictive loops and multi-pump loops you need to run a few test on before you install them in your PC.