Is 740 GPH overkill?

I would think, in a small application such as CPU cooling, that GPH would have a point to where it started giving you negative effects, as in the water is rushing through too fast to have time for the heat to be transfered to the water from the block.
 
xyoufailmex said:
I would think, in a small application such as CPU cooling, that GPH would have a point to where it started giving you negative effects, as in the water is rushing through too fast to have time for the heat to be transfered to the water from the block.
Click to expand...

Since a water is in a loop, no matter how fast the water goes, it will spend the same amount of time in the waterblock.

You can get such a large pump that it transfers too much heat into the loop, though.
 
xyoufailmex said:
I would think, in a small application such as CPU cooling, that GPH would have a point to where it started giving you negative effects, as in the water is rushing through too fast to have time for the heat to be transfered to the water from the block.
Click to expand...

nope. doesn't work that way. you want the maximum temperature difference between the copper and the water. water just sitting in the block = bad. the only thing he'll really need to worry about is making sure his reservoir (assuming he's using one) is big enough to avoid having so much cavitation that air gets into the lines. other than that it's just a matter of making sure his hose clamps are tight enough. oh, and having enough room for the pump is a plus, too.
 
flak said:
nope. doesn't work that way. you want the maximum temperature difference between the copper and the water. water just sitting in the block = bad. the only thing he'll really need to worry about is making sure his reservoir (assuming he's using one) is big enough to avoid having so much cavitation that air gets into the lines. other than that it's just a matter of making sure his hose clamps are tight enough. oh, and having enough room for the pump is a plus, too.
Click to expand...


You're right about the flowrate, water doesn't need any residence time in order to soak up heat. However, cavitation is nothing to do with the water in the reservoir. It occurs when local water pressure is reduced enough to induce boiling, which creates pockets of vapor that collapse almost instantaneously. Air getting in the water can be due to water sloshing around in the reservoir, which I think is what you were getting at.
 
ya, that's it. i had too small a reservoir once and the water sloshed around so much all kinds of air was getting into the lines.
 
all i know is the faster the wind blows the colder i get... water would be even worse. :D
 
Make sure your lines are secure, that will create quite a bit of pressure in the tubes before your block, if it's very restrictive.
 
i have one cooling loop that uses the old design Rainbow Lifeguard Quiet One -- 1140gph - no probs yet. If you are worried about extra heat in the water from the pump, just kick up the size of your heat exchanger a little. :)
 
zer0signal667 said:
You're right about the flowrate, water doesn't need any residence time in order to soak up heat. However, cavitation is nothing to do with the water in the reservoir. It occurs when local water pressure is reduced enough to induce boiling, which creates pockets of vapor that collapse almost instantaneously. Air getting in the water can be due to water sloshing around in the reservoir, which I think is what you were getting at.
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Cavitation occurs in some loops where the pump is restricted on the inlet. People put reseviors before the inlet of the pump because this is naturally the least restrictive part of the loop and also serves to even out pressures when there is a little bit of air in it and helps prime the pump. I had 2 via aquas die from cavitation before I discovered this.
 
killernoodle said:
Cavitation occurs in some loops where the pump is restricted on the inlet. People put reseviors before the inlet of the pump because this is naturally the least restrictive part of the loop and also serves to even out pressures when there is a little bit of air in it and helps prime the pump. I had 2 via aquas die from cavitation before I discovered this.
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Not trying to be picky but I don't think what happens in a water cooling setup is cavitation.

cav·i·ta·tion:
n.
1. The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.

For this to happen in a w/c setup you would need a seriously powerful pump. I believe you are talking about "pockets" of air getting trapped in the pump, probably causing heat and friction buidup resulting in pump failure. This is the reason I use a T line on the inlet of my pump, so I can prime it.
 
The problem with a pump like that is, it'll be dumping all kinds of heat into your loop. So much so, that it counters the performance benifit from high flow...
 
Maximus825 said:
The problem with a pump like that is, it'll be dumping all kinds of heat into your loop. So much so, that it counters the performance benifit from high flow...
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exactly. For example comparing two different iwaki pumps the md-20 and 30. The 30 is a poor choice, even though it has better specs it puts a lot more heat into the loop which more than counteracts the advantage over the md-20, making the weaker pump the md-20 the better choice.

In the world of watercooling pumps bigger does not mean better.
 
Anything much over 350 GPH and 9' head is getting to the point of diminishing returns and like these guys are saying, only addes extra heat to the water. There is also the possibility of cavitation if the pump is powerful enough. (although, in a watercooling loop, this is debatable as there has been no conclusive testing that I've seen confirming or dispelling this) Your best bet is keeping it under 400 GPH and between 5' - 9' of head.
 
Gotta side with plywood99 on this one.

Cavitation only comes into play when you're doing some serious work on the fluid.

eg.
Submarine propellers have some issues with cavtation.
Steam turbine blades @ the power plant also suffer from cavitation effects.

--
--
I've sucked some air bubbles into a pump, and they make all kinds of noise.. you can even get a mini whirl-pool going on if you're not careful... this is not cavitation.
 
Cavitation is not only limited to large propellors and such. It is only a product of pressure really, the pressure at the front of a pump can be so low that the impellor cavitates (basically creates its own air bubbles with no air to make bubbles from) on itself. You can achieve the same effect if you take your arm and move it rapidly through water.You will notice that you will leave an air pocket following your arm, but there is no air to get in there. That is cavitation.
 
Jason711 said:
all i know is the faster the wind blows the colder i get... water would be even worse. :D
Click to expand...
This works with people but not anything else. Wind Chill does not effect metal. If it's 40F and the wind is blowing 10 mph, the wind chill will make it feel like it's 34F. It isn't 34F it just feels 34F. So no matter how fast the water is moving it will still be the same temperature, all other things being equal.

The formula for figuring out wind chill is:
Wind Chill(F) = 33.74 + 0.6215T - 33.75(V^0.16) + 0.4275T(V^0.16)
where T = air temperature in F and V = wind speed in mph
​
 
I have this pump upgraded from a 1300. all i can say is that my temps dropped 6c at load I'm a happy man. but you have to get size converters to get it to take 1/2 or 3/8. do the sound mod then seal that sucker quick leaks like a sieve I used plumbers goop. worked like a charm
 
WheresWaldo said:
This works with people but not anything else. Wind Chill does not effect metal. If it's 40F and the wind is blowing 10 mph, the wind chill will make it feel like it's 34F. It isn't 34F it just feels 34F. So no matter how fast the water is moving it will still be the same temperature, all other things being equal.

The formula for figuring out wind chill is:
Wind Chill(F) = 33.74 + 0.6215T - 33.75(V^0.16) + 0.4275T(V^0.16)
where T = air temperature in F and V = wind speed in mph
​
Click to expand...


Regardless of wind chill, heat transfer increases as fluid velocity increases.
 
thewhiteguy said:
Make sure your lines are secure, that will create quite a bit of pressure in the tubes before your block, if it's very restrictive.
Click to expand...

it will also cause quite a bit of pressure in the tubes themselves. Make sure the tubes can withstand the amount of pressure
 
killernoodle said:
Cavitation is not only limited to large propellors and such. It is only a product of pressure really, the pressure at the front of a pump can be so low that the impellor cavitates (basically creates its own air bubbles with no air to make bubbles from) on itself. You can achieve the same effect if you take your arm and move it rapidly through water.You will notice that you will leave an air pocket following your arm, but there is no air to get in there. That is cavitation.
Click to expand...


In a closed loop system such as pc water cooling cavitation is not the culprit. If that was the case then it would not be advisable to shut off your pump, since turning it back on would cause a sudden decrees in back pressure, aka "cavitation" , and as you said in a prior post causing pump failure.

You would need tremendous head pressure in a w/c to cause true cavitation. By tremendous I mean much more than the pressure put out by typical pc/aquarium/pond pumps.
 
Way to go!

http://en.wikipedia.org/wiki/Cavitation

It can happen in any manner of pumps, all that it needs is a partial or total blockage of the inlet of the impellor and the impellor to "suck air from nowhere". If your pump does this, it is cavitating. There is no other explanation for it.

I had 2 via aquas die form cavitation, they became noisy, then rattly, then they simply were untolerable.
 
killernoodle said:
Way to go!

http://en.wikipedia.org/wiki/Cavitation

It can happen in any manner of pumps, all that it needs is a partial or total blockage of the inlet of the impellor and the impellor to "suck air from nowhere". If your pump does this, it is cavitating. There is no other explanation for it.

I had 2 via aquas die form cavitation, they became noisy, then rattly, then they simply were untolerable.
Click to expand...

Via Aquas are notorious for being noisy, unless you do the super-glue the impeller to the shaft trick.
Also in your link, they spoke of physical damage appearing on the impeller, I quote: An impeller that has been operating under a suction cavitation condition has large chunks of material removed from its face causing premature failure of the pump." Were your impellers physically damaged?

This, again, sounds like far more powerful pumps than are used in computers.

I believe your pump problems came from the very pump you chose to use, Via Aquas. I've read on other forums of them having SIDS, er that is SPDS, sudden pump death syndrome. :D
 
Because of the materials used in a pump and its low power, the effect of cavitation can range from noise that never ends to premature pump failure, but is usually not very widespread.

Read.

There is no difference between the physics of a small and the physics of a large pump. The same rules of pressure, velocity, and temperature apply in smaller sizes. Even the amount of submersion is applicable too, as you can test this theory in a kitchen sink. If you bring a powerful water pump close to the surface, it will create a vortex and begin to suck in air. If you block the impellor it will usually begin to cavitate, even if you cant see it. You can usually hear it though if it is a powerful pump.
 
killernoodle said:
test this theory in a kitchen sink. If you bring a powerful water pump close to the surface, it will create a vortex and begin to suck in air. If you block the impellor it will usually begin to cavitate, even if you cant see it. You can usually hear it though if it is a powerful pump.
Click to expand...

By creating the vortex, you are allowing air to enter the pump. So the pump is choking on an air pocket, not cavitation.

Also, many submersible pumps come with a flow adjuster on the inlet side. Why would they do this if restricting flow would cause cavitation and then pump failure??

Nevertheless, this is my last post on the subject.
 
Throttle the outlet (throttling the inlet leads to cavitation, cavitation leads to message board hate, hate leads to the dark side). Or, even better, buy a pump of the right strength.
 
The main consideration is how much heat a pump dumps into the system. At some point, (over 50 watts) the amount of heat a pump generates negates any benefit higher output brings. Where that point is depends on the rad/fan combo used. Check out this thread, the best testing I've ever seen, as well as input from the guys that actually design WCing systems for a living:

http://forums.procooling.com/vbb/showthread.php?t=10825&page=1&pp=25
 
Jonsey said:
The main consideration is how much heat a pump dumps into the system. At some point, (over 50 watts) the amount of heat a pump generates negates any benefit higher output brings. Where that point is depends on the rad/fan combo used. Check out this thread, the best testing I've ever seen, as well as input from the guys that actually design WCing systems for a living:

http://forums.procooling.com/vbb/showthread.php?t=10825&page=1&pp=25
Click to expand...


Now the question remains, where in America can you get an Iwaki RD-30.
 
mwarps said:
Now the question remains, where in America can you get an Iwaki RD-30.
Click to expand...

From the link above:

+20.7C => Iwaki RD-30 @ 18.0v
+20.8C => 2 x Swiftech MCP600 @ 13.8v (series)
+20.9C => Swiftech MCP600 @ 13.8v
+21.1C => Iwaki MD-20RZ @ 60Hz
+21.1C => 2 x Swiftech MCP600 @ 12.0v (series)
+21.2C => Iwaki MD-20RZ @ 50Hz
+21.4C => Swiftech MCP600 @ 12.0v
+21.4C => 2 x Eheim 1048 (series)
+21.5C => Iwaki MD-15R @ 60Hz
+21.6C => Swiftech MCP650 @ 12.0v
+21.6C => Iwaki MD-30RZ @ 50Hz
+21.7C => Iwaki MD-30RZ @ 60Hz
+21.9C => Eheim 1250
+22.1C => Laing DDC @ 12.0v
+22.3C => Eheim 1048
+23.3C => Eheim 1046

Not a whole lot of performance difference between the top contenders. I would come down to price/availbility for me.
 
Jonsey said:
From the link above:

+20.7C => Iwaki RD-30 @ 18.0v
+20.8C => 2 x Swiftech MCP600 @ 13.8v (series)
+20.9C => Swiftech MCP600 @ 13.8v
+21.1C => Iwaki MD-20RZ @ 60Hz
+21.1C => 2 x Swiftech MCP600 @ 12.0v (series)
+21.2C => Iwaki MD-20RZ @ 50Hz
+21.4C => Swiftech MCP600 @ 12.0v
+21.4C => 2 x Eheim 1048 (series)
+21.5C => Iwaki MD-15R @ 60Hz
+21.6C => Swiftech MCP650 @ 12.0v
+21.6C => Iwaki MD-30RZ @ 50Hz
+21.7C => Iwaki MD-30RZ @ 60Hz
+21.9C => Eheim 1250
+22.1C => Laing DDC @ 12.0v
+22.3C => Eheim 1048
+23.3C => Eheim 1046

Not a whole lot of performance difference between the top contenders. I would come down to price/availbility for me.
Click to expand...

There is a decent amont of difference in the power consumption and noise that those top pumps make. I hear that RD-30 is absolutely silent at 18V and only uses about 30 watts or so. Also, that pump has a longer MTBF than most of the pumps on that list too. Just a little food for thought...

And if anyone knows where I can get an RD-30 in the Sates for a reasonable price (under 230... preferrably under 200) please PM me! :D
 
Jonsey said:
From the link above:

+20.7C => Iwaki RD-30 @ 18.0v
+20.8C => 2 x Swiftech MCP600 @ 13.8v (series)
+20.9C => Swiftech MCP600 @ 13.8v
+21.1C => Iwaki MD-20RZ @ 60Hz
+21.1C => 2 x Swiftech MCP600 @ 12.0v (series)
+21.2C => Iwaki MD-20RZ @ 50Hz
+21.4C => Swiftech MCP600 @ 12.0v
+21.4C => 2 x Eheim 1048 (series)
+21.5C => Iwaki MD-15R @ 60Hz
+21.6C => Swiftech MCP650 @ 12.0v
+21.6C => Iwaki MD-30RZ @ 50Hz
+21.7C => Iwaki MD-30RZ @ 60Hz
+21.9C => Eheim 1250
+22.1C => Laing DDC @ 12.0v
+22.3C => Eheim 1048
+23.3C => Eheim 1046

Not a whole lot of performance difference between the top contenders. I would come down to price/availbility for me.
Click to expand...
I would agree, if the MCP600 were still available, but it's not. The 650 seems right there with the 600, I'd say it's within the noise. I've got a month or so yet before I buy, so that gives me tiem to hunt for the Iwaki and decide.
 
mwarps said:
I would agree, if the MCP600 were still available, but it's not. The 650 seems right there with the 600, I'd say it's within the noise. I've got a month or so yet before I buy, so that gives me tiem to hunt for the Iwaki and decide.
Click to expand...

The MCP600 from swiftech is technically no longer availible, but there are some companies around that sell the same pump. Cooltechnica sells it: the AquaXtreme 50Z-DC12.
 
I don't see how some can justify spending an extra hundred bucks for that tiny bit of performance. I'm happy with the Liang D4 that I have, except for the noise. If I turn down my fans to slow speed, I can definitely hear it.
 
it works with everything, just not as dramatically. Pushing more air or water past something faster keeps the temperature difference as high as possible. Heat transfer is directly related to the difference in temperature.

WheresWaldo said:
This works with people but not anything else. Wind Chill does not effect metal. If it's 40F and the wind is blowing 10 mph, the wind chill will make it feel like it's 34F. It isn't 34F it just feels 34F. So no matter how fast the water is moving it will still be the same temperature, all other things being equal.

The formula for figuring out wind chill is:
Wind Chill(F) = 33.74 + 0.6215T - 33.75(V^0.16) + 0.4275T(V^0.16)
where T = air temperature in F and V = wind speed in mph
​
Click to expand...
 
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