Messed up my loop

R B Customs · 19 May 2006 at 21:24

Ladforce said:
as long as the loop is closed the pressure at any point will be the same as liquid is incompressible.

i was goign to make that point but you have beaten me to it

. i will add though that 'gravity doesnt exist' in watercooling either,its common belief that it is easier to pump water DOWN ( asin with gravity) then it is to push water UP ( against gravity) - WRONG. the pump doesnt just PUSH water, it also PULLS it with equal force, because of this theres no low spots in pressure. the only thign that varies is the SPEED of the water as it passes through thinner / thicker walled tubing / barbs. but that doesnt have much to do with anything

good Point
think of it as a Waltzer at a fair ground... one cart cannot speed up nor slow down as theres carts beind it and infront. the flow of the carts are always the same and never gain / lose power at any point of the ride
Rick

Ladforce · 19 May 2006 at 21:46

R B CUSTOMS said:
i was goign to make that point but you have beaten me to it . i will add though that 'gravity doesnt exist' in watercooling either,its common belief that it is easier to pump water DOWN ( asin with gravity) then it is to push water UP ( against gravity) - WRONG. the pump doesnt just PUSH water, it also PULLS it with equal force, because of this theres no low spots in pressure. the only thign that varies is the SPEED of the water as it passes through thinner / thicker walled tubing / barbs. but that doesnt have much to do with anything
good Point
think of it as a Waltzer at a fair ground... one cart cannot speed up nor slow down as theres carts beind it and infront. the flow of the carts are always the same and never gain / lose power at any point of the ride
Rick

what degree did you do mate?

sablabra · 19 May 2006 at 23:31

Ladforce said:
what degree did you do mate?

I think he might passed elementary school, although that is questionable

But seriously, try making a loop with ten feets off pipes straight up, then down again. I'll bet a penny the flow will be BAD, if the water goes around at all, that is...

***F1ZZY*** · 20 May 2006 at 08:24

Ladforce said:
as long as the loop is closed the pressure at any point will be the same as liquid is incompressible.

Water is not compressible true, but the tubes are very flexible.

You guys never heard the terms "pressure drop" when reading watercooling reviews about blocks?

Are you telling me that the pressure before the pump and after the pump are the same?

RB CUSTOMS even says it pulls one side and pushes the other.

1 Flow rate is constant throughout the loop
2 Velocity varies depending upon tube/vessel/waterchannel etc cross sectional area (diameter)
3 Pressure most certainly differs around the loop.

As a real world example, I have a res before my pump and a fill line connected to the res. Fill line is 3/8 and loop is 1/2". When I start the pump the fill line water level drops about 1 inch and returns when the pump stops.

Where does this water temporarily go?

(HINT - I have an RBX high resistance (read: pressure drop) block immediately after the pump and FLEXIBLE tygon tubing)

For all elimentary grads and subscribers to mythology, have a read of THIS

***F1ZZY*** · 20 May 2006 at 09:01

I have always thought of the watercooling loop similar to a DC circuit.

With interchangeable terms

Battery = Pump
Amps = Flowrate
Volts = Pressure

In a DC circuit, amps are constant and voltage drops each time resistance is encountered.

In water cooling, flowrate is constant and pressure drops each time resistance is encountered.

Just found THIS to confirm my thoughts over the last few years.

iraiguana · 20 May 2006 at 09:20

changes in volume are explained by the fact u have a liquid and a heat source, which is different to ambient would be a major factor for your total volume of liquid changing. IF it was a perfect liquid it would also undergo no compression under pressure, but its not its water! (h-bonding etc etc) with random crap in.

//edit: not saying blocks do not affect flow here, just comments as to volume changes should be seen. //

Ladforce · 20 May 2006 at 10:38

***F1ZZY*** said:
Water is not compressible true, but the tubes are very flexible.

You guys never heard the terms "pressure drop" when reading watercooling reviews about blocks?

Are you telling me that the pressure before the pump and after the pump are the same?

RB CUSTOMS even says it pulls one side and pushes the other.

1 Flow rate is constant throughout the loop
2 Velocity varies depending upon tube/vessel/waterchannel etc cross sectional area (diameter)
3 Pressure most certainly differs around the loop.

As a real world example, I have a res before my pump and a fill line connected to the res. Fill line is 3/8 and loop is 1/2". When I start the pump the fill line water level drops about 1 inch and returns when the pump stops.

Where does this water temporarily go?

(HINT - I have an RBX high resistance (read: pressure drop) block immediately after the pump and FLEXIBLE tygon tubing)

For all elimentary grads and subscribers to mythology, have a read of THIS

the pressure only drops as the pump cannot supply the force required to keep it the same when it meets resistance. if you had an infinitely powerful pump that had no drop when it meets resistance the pressure would be equal at all points in the loop.

***F1ZZY*** · 20 May 2006 at 11:23

iraiguana said:
changes in volume are explained by the fact u have a liquid and a heat source, which is different to ambient would be a major factor for your total volume of liquid changing. IF it was a perfect liquid it would also undergo no compression under pressure, but its not its water! (h-bonding etc etc) with random crap in.

//edit: not saying blocks do not affect flow here, just comments as to volume changes should be seen. //

Volume (water level) changes are 2-fold.

A quick on-off of the pump sees the volume in the fill tube go down and return to its normal point.

Running the system for a while sees as slow increase in volume due to expansion of liquid with temperature increase.

***F1ZZY*** · 20 May 2006 at 11:32

Ladforce said:
the pressure only drops as the pump cannot supply the force required to keep it the same when it meets resistance. if you had an infinitely powerful pump that had no drop when it meets resistance the pressure would be equal at all points in the loop.

Absolute fart.

An infinitely powerful pump would create a massive (infinite) pressure differential accross the resistance and thus result in massive flow rate.

[ I don't mean massive as in having lots of mass; just a figure of speach to indicate a lot, or infinite if you are that way inclined]

The reason it flows is the loop has high pressure at the pump outlet and low pressure at the inlet.

People seem to think that just because you can't compress a [perfect] liquid, that you cannot exert pressure to it.

If pressure was equal throughout your loop, then you would have NO FLOW.

Ladforce · 20 May 2006 at 11:34

***F1ZZY*** said:
Volume (water level) changes are 2-fold.

A quick on-off of the pump sees the volume in the fill tube go down and return to its normal point.

Running the system for a while sees as slow increase in volume due to expansion of liquid with temperature increase.

the on off of the pump causing the level to drop is surely just because the tubing expands slightly when under pressure?

***F1ZZY*** · 20 May 2006 at 11:36

Ladforce said:
the on off of the pump causing the level to drop is surely just because the tubing expands slightly when under pressure?

WHAHOO.... gold star time.

Ladforce · 20 May 2006 at 11:36

***F1ZZY*** said:
Absolute fart.

An infinitely powerful pump would create a massive (infinite) pressure differential accross the resistance and thus result in massive flow rate.

[ I don't mean massive as in having lots of mass; just a figure of speach to indicate a lot, or infinite if you are that way inclined]

The reason it flows is the loop has high pressure at the pump outlet and low pressure at the inlet.

People seem to think that just because you can't compress a [perfect] liquid, that you cannot exert pressure to it.

If pressure was equal throughout your loop, then you would have NO FLOW.

when i say infinitely i mean it does not drop in pressure due to resistance rather than it actually having an incredible pressure on the water.

Ladforce · 20 May 2006 at 11:56

ok i think we are getting confused...just realised..when i said about the pressure drop in the loop i mean a loop of tubing will have equal pressure throughout as the velocity will remain constant, not taking into account friction with the wall.

you are correct that the pressure will drop over the block as the velocity increases and due to the conservation of energy obviously the pressure will drop. however, when the water gets to the other side of the block and into the tube again, it will have the same pressure and velocity as it did when it entered the block (again negating the effect of friction). this also assumes the gravitational potential energy is not taken into account as the gpe in a closed loop has gpe = 0.

***F1ZZY*** · 20 May 2006 at 11:58

Ladforce said:
when i say infinitely i mean it does not drop in pressure due to resistance rather than it actually having an incredible pressure on the water.

That's not possible. You cannot ignore resistance just if you add a more powerful pump.

A more powerful pump will increase flowrate for the given resistance of the loop, it will not have zero pressure drop.

Got me thinking though, what if pump was infinite and resistance was a theoretical zero. Water velocity would be infinite too....pump explodes I think.

Ladforce · 20 May 2006 at 12:00

***F1ZZY*** said:
That's not possible. You cannot ignore resistance just if you add a more powerful pump.

A more powerful pump will increase flowrate for the given resistance of the loop, it will not have zero pressure drop.

Got me thinking though, what if pump was infinite and resistance was a theoretical zero. Water velocity would be infinite too....pump explodes I think.

i stand corrected about the pump

***F1ZZY*** · 20 May 2006 at 12:09

Ladforce said:
ok i think we are getting confused...just realised..when i said about the pressure drop in the loop i mean a loop of tubing will have equal pressure throughout as the velocity will remain constant, not taking into account friction with the wall.

you are correct that the pressure will drop over the block as the velocity increases and due to the conservation of energy obviously the pressure will drop. however, when the water gets to the other side of the block and into the tube again, it will have the same pressure and velocity as it did when it entered the block (again negating the effect of friction). this also assumes the gravitational potential energy is not taken into account as the gpe in a closed loop has gpe = 0.

For you first scenario, yes I think that MIGHT work. IF zero resistance in the loop. It would start (when pump switched on) with no flow and create high pressure at the outlet and low at the inlet. Water would accelerate. We would get EQUAL pressure (I think) once terminal velocity had been reached (dictated by rotor speed of the motor)and there was no resistance.

Your 2nd statement is totally wrong. Pressure drop at block, what gives it more pressure after to make it the same as before??? you have another pump here???

/takes gold star back/

***F1ZZY*** · 20 May 2006 at 12:30

Assuming your block has resistance and less cross sectional area (like most do)

Pressure before the block will be high.

Flow rate will be equal before, during and after.

Velocity will be at its highest in the block.

Pressure after the block will be lower.
---------------------------------------------------------------------------
Water cooling loops have resistance.
Pumps create a pressure differential.
Water flows from high to low.

Ladforce · 20 May 2006 at 14:00

***F1ZZY*** said:
Assuming your block has resistance and less cross sectional area (like most do)

Pressure before the block will be high.

Flow rate will be equal before, during and after.

Velocity will be at its highest in the block.

Pressure after the block will be lower.
---------------------------------------------------------------------------
Water cooling loops have resistance.
Pumps create a pressure differential.
Water flows from high to low.

for the pressure after the block to be lower, the velocity must be higher than when it entered the block..is this the case?

***F1ZZY*** · 20 May 2006 at 15:24

Wrong.

Flow rate is equal anywhere in a loop.

Since the tubing into the block and out of the block is the same (CSA), then the velocity is the same (in the tubes).

Since area in the block is less, velocity is higher there.

This is exaggerated for impingement blocks (like the Storm in the OP ; sorry for going off on one too, but you did ask

)

I'm struggling for an analogy here......... but think of a syringe, 1/2" diam plunger and a normal needle nozzle. You squeeze like hell and exert a lot of pressure in the plunger tube and can get the water jet shooting 10 feet. You are a good shot and shoot this jet into a funnel which is connected to a 1/2" diam pipe.

The flow rate is the same anywhere.
The velocity is way higher during the needle section.

Confine all this into a loop and have a "rotary plunger" then that's a WC loop.