Thread: cheap hose
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Old March 15, 2013, 10:08 AM
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great_big_abyss great_big_abyss is offline
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Quote:
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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