Water velocity question

zee bee · 02-14-2005, 11:21 AM

What is the effect on water velocity in a cooling loop if it is split by a "Y" splitter?

Perhaps this will help elucidate my question a little bit better:

Consider a 3 barb block like the RBX or WW. Is the water exiting each of the two outlet barbs with the same velocity as the inlet barb? Or is it exiting with half of the original velocity through one tube and half through the other.

The latter is a point a friend of mine brought up in a discussion of loops running in parallel with blocks, such as impingement blocks, that benefit from high water velocity. It doesn't make much sense to me. I think the velocity is constant throughout the whole loop.

Any thoughts?

Butcher · 02-14-2005, 11:43 AM

Velocity will be halved - think about it.

zee bee · 02-14-2005, 11:52 AM

Right, then following that logic, the velocity would only be halved IF each branch of tubing were to have equal flow resistence. So in a parallel loop, the line with less resistance would have greater flow.

I think I am beginning to understand, yes?

JamesAvery22 · 02-14-2005, 11:56 AM

Quote:

Originally Posted by zee bee

Right, then following that logic, the velocity would only be halved IF each branch of tubing were to have equal flow resistence. So in a parallel loop, the line with less resistance would have greater flow.

I think I am beginning to understand, yes?

Correct. Thats why putting your CPU block and NB block in parrallel is usually a bad idea as the NB block will usually have the least resistance, giving your CPU block pretty bad flow. Usually

killernoodle · 02-14-2005, 01:14 PM

Well, halving the flow is never a good way to start off feeding a waterblock anyways

JWFokker · 02-14-2005, 05:15 PM

Flow would halve, definitely, but you could maintain velocity if you used a smaller ID tubing.

Long Haired Git · 02-14-2005, 10:05 PM

What does "velocity" mean to you?
The flow, in litres per minute is constant from the outlet of the pump to the inlet of the pump. The velocity of the liquid, expressed as meters per second, changes constantly in order to keep the flow (LPM) constant despite changes in diameter and the parallel paths possible.
Eg: In a radiator there may be 5 parallel tubes, so assuming equal resistance, each tube gets 1/5th the overall flow rate (assuming all liquid goes through the radiator). Each tube may be only 1/10th the overall cross sectional area of the tubing in use though, in which case the velocity of the coolant will increase to be twice as fast as it is in the tubing.

Kobuchi · 02-14-2005, 11:56 PM

This is all true, but friction does take its toll on velocity. Friction in a "Y". More pipe surface, more friction. You can subdivide and subdivide, but at some point all those little pipes will be passing less water than tear membranes.*

You can get a better handle on this, zee bee, by figuring what the pressure is at a given section, and then how that pressure causes flow.

*

Valentine's Day and wife is out of town.

02-14-2005, 11:21 AM	#1
zee bee Cooling Neophyte Join Date: Nov 2004 Location: Florida Posts: 14	Water velocity question What is the effect on water velocity in a cooling loop if it is split by a "Y" splitter? Perhaps this will help elucidate my question a little bit better: Consider a 3 barb block like the RBX or WW. Is the water exiting each of the two outlet barbs with the same velocity as the inlet barb? Or is it exiting with half of the original velocity through one tube and half through the other. The latter is a point a friend of mine brought up in a discussion of loops running in parallel with blocks, such as impingement blocks, that benefit from high water velocity. It doesn't make much sense to me. I think the velocity is constant throughout the whole loop. Any thoughts?

02-14-2005, 11:43 AM	#2
Butcher Thermophile Join Date: May 2001 Location: UK Posts: 1,064	Velocity will be halved - think about it. __________________ Once upon a time, in a land far far away...

02-14-2005, 01:14 PM	#5
killernoodle Thermophile Join Date: Sep 2002 Location: Charlotte, NC Posts: 1,014	Well, halving the flow is never a good way to start off feeding a waterblock anyways __________________ I have a nice computer.

02-14-2005, 10:05 PM	#7
Long Haired Git Cooling Savant Join Date: Jan 2003 Location: Sydney, Oz Posts: 336	What does "velocity" mean to you? The flow, in litres per minute is constant from the outlet of the pump to the inlet of the pump. The velocity of the liquid, expressed as meters per second, changes constantly in order to keep the flow (LPM) constant despite changes in diameter and the parallel paths possible. Eg: In a radiator there may be 5 parallel tubes, so assuming equal resistance, each tube gets 1/5th the overall flow rate (assuming all liquid goes through the radiator). Each tube may be only 1/10th the overall cross sectional area of the tubing in use though, in which case the velocity of the coolant will increase to be twice as fast as it is in the tubing. __________________ Long Haired Git "Securing an environment of Windows platforms from abuse - external or internal - is akin to trying to install sprinklers in a fireworks factory where smoking on the job is permitted." (Prof. Gene Spafford) My Rig, in all its glory, can be seen best here AMD XP1600 @ 1530 Mhz \| Soyo Dragon + \| 256 Mb PC2700 DDRAM \| 2 x 40 Gb 7200rpm in Raid-0 \| Maze 2, eheim 1250, dual heater cores! \| Full specifications (PCDB)

02-14-2005, 11:52 AM	#3
zee bee Cooling Neophyte Join Date: Nov 2004 Location: Florida Posts: 14	Right, then following that logic, the velocity would only be halved IF each branch of tubing were to have equal flow resistence. So in a parallel loop, the line with less resistance would have greater flow. I think I am beginning to understand, yes?

02-14-2005, 05:15 PM	#6
JWFokker Cooling Savant Join Date: May 2004 Location: Kingston, NY Posts: 269	Flow would halve, definitely, but you could maintain velocity if you used a smaller ID tubing.

02-14-2005, 11:56 PM	#8
Kobuchi Cooling Savant Join Date: Jan 2003 Location: BC, Canada Posts: 313	This is all true, but friction does take its toll on velocity. Friction in a "Y". More pipe surface, more friction. You can subdivide and subdivide, but at some point all those little pipes will be passing less water than tear membranes.* You can get a better handle on this, zee bee, by figuring what the pressure is at a given section, and then how that pressure causes flow. * Valentine's Day and wife is out of town.

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