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Old March 15, 2013, 09:48 AM
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Quote:
Originally Posted by great_big_abyss View Post
Shouldn't apply, since it's a closed system. Theres's the same amount of water going 'down' as there is going 'up'. The weight of the water going 'down' cancels out the weight of the water going UP, therefore head calculations don't figure into it. The only thing the pump has to overcome is the friction of the water against the tubing walls, and the pressure created by the blocks.
Certain things are always true with centrifugal pumps

pumps simply will not deliver to heights above their rated head, and delivery falls off rapidly as max head is approached. Small tubing and tight bends just add insult to injury to delivery rate.

now if were talking displacement pump (gear/vane) i agree
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Old March 15, 2013, 10:08 AM
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Originally Posted by KaptCrunch View Post
Certain things are always true with centrifugal pumps

pumps simply will not deliver to heights above their rated head, and delivery falls off rapidly as max head is approached. Small tubing and tight bends just add insult to injury to delivery rate.

now if were talking displacement pump (gear/vane) i agree

The type of pump has nothing to do with it. There are four kinds of head: Static Head, Friction Head, Pressure Head, and Velocity head. So, just to make sure we're talking about the same thing...

Static head represents the net change in height, in feet, that the pump must overcome. It applies only in open systems. In a closed loop, the static head is zero because the fluid on one side of the system pushes the fluid up the other side of the system, so the pump does not need to overcome any elevation.

Friction Head (aside from being the type that Perinium's mom is best versed in) is also called pressure drop. When fluid flows through any system component, friction results. This causes a loss in pressure. components causing friction include rads, tubing, blocks, etc. The pump must overcome this friction. Friction is usually expressed in units called 'feet of head'. A foot of friction head is equal to lifting the fluid one foot of static height.

Pressure Head exists when liquid is pumped from a vessel at one pressure to a vessel at another pressure.

Velocity Head exists when accelerating water from a standstill or low velocity at the starting point to a higher velocity at the ending point. In closed systems the starting point is the same as the ending point. Therefore beginning velocity equals the final velocity, so velocity head is not a consideration.

In a PC watercooling application, Friction Head is the only head that must be accounted for. The pump must be strong enough to overcome the friction resulting from the tubing and all the peripherals (blocks, rads, res, etc). Add more tubing (to run to a cold room) and you'll add more friction, possibly necessitating a larger or second pump.
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Old March 15, 2013, 11:56 AM
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and head shut off is inherant of centerifugal

positive pump has no shutoff head like centrifugal pumps.

with at most computer cases loop elevation max 3ft where laing ddc has 13ft of head on 3/8 barb's

now go outside of 13ft = no flow head shut-off point of pump
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Old March 15, 2013, 06:59 PM
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Originally Posted by KaptCrunch View Post
same as linar if were on same floor

so would need second pump along loop before 10ft head mark
Water exterts no pressure horizontally... only vertically dude. There might be a bit of static load but most pumps can deal with this. It also doesn't matter how big or small the container at the top or bottom is the weight of water never changes if it is above 4 degrees C. And exactly what Abyss said... what goes up must come down so it cancels out.

Water weighs .433 pounds per square inch per foot of height. You are correct about the head pressure... if you can only get 10 feet of head pressure and you have to go 11 feet you will have zero pressure. You can solve this problem by putting another pump back to back if you choose to increase head pressure or you can purchase a better pump.

If you need 10 psig to go 10 feet up and require 10psig at the top of 10 feet you need a pump that does 20psig. If you wanna get really technical you can also add in pressure reducing valves and an expansion tank and throw a bigger pump at it... hell throw in a lift check valve while your at it. :P

*had to fix my math there... I'm tired.
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Last edited by clshades; March 15, 2013 at 07:53 PM.
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Old March 15, 2013, 07:04 PM
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use a filter same with PVC tubing

You do NOT want to deal with this stuff man... Pex is a FAR better solution and much cheaper.
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Old March 16, 2013, 04:45 AM
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Pex is far more expensive than the tube I posted. Also the tube I show doesn't require any Pex fittings. It works just fine with standard water cooling fittings. And it's not actually cheap so much as inexpensive.
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Old March 16, 2013, 08:08 AM
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Quote:
Originally Posted by clshades View Post
Water exterts no pressure horizontally... only vertically dude. There might be a bit of static load but most pumps can deal with this. It also doesn't matter how big or small the container at the top or bottom is the weight of water never changes if it is above 4 degrees C. And exactly what Abyss said... what goes up must come down so it cancels out.

Water weighs .433 pounds per square inch per foot of height. You are correct about the head pressure... if you can only get 10 feet of head pressure and you have to go 11 feet you will have zero pressure. You can solve this problem by putting another pump back to back if you choose to increase head pressure or you can purchase a better pump.

If you need 10 psig to go 10 feet up and require 10psig at the top of 10 feet you need a pump that does 20psig. If you wanna get really technical you can also add in pressure reducing valves and an expansion tank and throw a bigger pump at it... hell throw in a lift check valve while your at it. :P

*had to fix my math there... I'm tired.
yes your pump is rated by kinetic energy of 10ft

that is all it can move from the rotor/impeller
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Old March 16, 2013, 05:10 PM
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Quote:
Originally Posted by Hooded View Post
Pex is far more expensive than the tube I posted. Also the tube I show doesn't require any Pex fittings. It works just fine with standard water cooling fittings. And it's not actually cheap so much as inexpensive.

LOL... dude have you EVER used that stuff on long runs? It's pure garbage. Pex isn't that expensive even the fittings are cheap. $0.30-1.00 / foot tops man. That stuff isn't as cheap as you think and it's a nightmare to work with... half the time it's flattented out when you buy it.. pex never flattens out.
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Old March 24, 2013, 11:03 AM
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I have found with water cooling that cheap is not necessarily the same as good value.
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