Does pump speed matter?

Zabuzaxsta

n00b
Joined
Jan 19, 2012
Messages
31
The title says it all...I have a decent amount of money set aside and I can get a uber nice, extremely fast pump (1000+ lph) or I can go with a slower pump. My intuition says faster would be better. For example, the faster air travels through a radiator, the better cooling you get, so it seems the faster water travels through a CPU/GPU block, the better cooling you would get. However, most of the guides I read say pump speed really isn't an issue, and to focus on getting a powerful enough pump to push water through all your components.

The only thing I can think of that's relevant is that higher-speed pumps would seem to impart more heat to the water. This would, of course, be bad. My setup is going to be a CPU and two xfire GPUs on an RX 240 (that's a double-thick radiator, FYI) and an RX 120 (again, double thick). The case I have doesn't allow for a 360mm rad, so I had to split them up. Regardless, I'm debating whether to run them on a single loop or a dual loop (single loop performance vs. dual loop awesome factor), but I was just wondering if pump speed really mattered in either setup.

I guess my basic question is this: why doesn't pump speed matter for cooling efficiency?
 

oldbrave

Gawd
Joined
Oct 18, 2002
Messages
596
Actually with a 1000 lph pump the coolant wouldn't be spending enough time in the water block to absorb very much heat and also wouldn't be spending enough time in the rad's to transfer much heat. Most of the popular pumps today range anywhere from 7 lpm to 23 lpm with a head height of anywhere from 5 to 9 meters.

EDIT: Sorry, my bust on the flow rate Ya it's 7 to 23 Liters Per Minute not per hour.
 
Last edited:

Archmage

2[H]4U
Joined
Jul 13, 2000
Messages
3,023
http://martinsliquidlab.org/2011/09/26/i7-2600k-cpu-xspc-raystorm/7/ - XSPC Raystorm pump sensitivity data.

- Higher flow WILL produce lower temps. You can see that even with the Raystorm above, but the effect is negligible in most systems generally after about ~ 1gpm loop flow (depends on the block design) - http://skinneelabs.com/ - this site has a lot of data on CPU block performance vs flow-rate.

- Thus I'd recommend a regular Laing pump (Like the mcp-35x used in the test above (or maybe just the non-pwm Swiftech mcp355 (aka Laing DDC 3.2) or Koolance PMP-400 (aka DDC 3.25)), or a variant of the Laing D5 (Koolance makes both "strong" and RPM-sense versions, Swiftech makes the regular mcp655)).

- I'd go with a single loop (dual loops = 2 pumps = more heat, and you don't have much radiator area).
- I'd definitely get low-restriction blocks (like that XSPC Raystorm I linked. It's probably the best CPU block available, all things considered).
- Try to get data on the restrictiveness of your GPU blocks, and then consider running these in parallel (often the best option).

Edit: Here is some pump data:

- http://martinsliquidlab.org/2011/02/26/koolance-pmp-400-laing-ddc-3-25-cov-rp400/ - Koolance PMP-400 AKA Laing DDC 3.25 [high-RPM, can be undervolted slightly]
- http://martinsliquidlab.org/2011/02/25/swiftech-mcp-35x-reservoir/ - Swiftech mcp 35x = PWM speed-control version of DDC, highest peak RPM of DDC pumps.
- http://martinsliquidlab.org/2011/03/05/koolance-pmp-450s-d5-strong-pump/ - The STRONG D5...heh...it's strong. A bit like the DDC 3.25 = high RPM.
- http://martinsliquidlab.org/2011/04/03/koolance-pmp-450-d5-vario-pump/ - Koolance's RPM-sense version of the D5 vario (Swiftech's = mcp655, almost the same).
- http://martinsliquidlab.org/2011/03/10/pump-noise-testing-round-1/ - pump noise testing with various pump-top volutes. This shows that the Koolance acetal tops actually reduce pump noise more than expected (presumably due to their size)...also that pump decoupling is the most important factor. - He was able to undervolt DDC pumps to below 8V here, but I would recommend 9V and above.
http://martinsliquidlab.org/2011/02/25/swiftech-mcp-35x-reservoir/ - This one actually compares the 35x to the DDC 3.25 in-depth...

http://martinsliquidlab.org/2011/03/02/pump-decoupling-comparison-metal-vs-neoprene-vs-eggcrate/ - Pump Decoupling... it works.

If you actually read through that site, you should be able to make a great choice.
 
Last edited:

tangoseal

[H]F Junkie
Joined
Dec 18, 2010
Messages
9,286
Actually with a 1000 lph pump the coolant wouldn't be spending enough time in the water block to absorb very much heat and also wouldn't be spending enough time in the rad's to transfer much heat. Most of the popular pumps today range anywhere from 7 lph to 23 lph with a head height of anywhere from 5 to 9 meters.

Nope, Nada, Not True, zilcha, nopers.

Here is a really good write up for you to read:

Credit goes to Rogerdugans at overclockers.com....

Honestly read this, its worth it;s weight!

Does more water flow = better cooling?


I wrote this in an attempt to reduce a large amount of data (which was largely in one very informative thread which was 17 pages long) to one simple and fairly easy to read document.
The original thread is HERE for anyone who wishes to get more in-depth knowledge on this subject.



Heat Transfer

Heat transfer is the basis for ALL computer cooling systems; in water cooled computers we make this more complicated by using multiple heat transfers:
cpu core to water block
water block to water
water to radiator
radiator to air.

*Heat transfer works best with the biggest temp differential: ideal would be cold water to cpu and hot water in the radiator. We cannot achieve this because a closed loop will achieve equilibrium at some point. The principle holds true however- the most efficient transfer happens at the greatest temperature differential, therefore higher flow rates will always help with all other variables remaining the same.
* It is the Heat Transfer that we want to maintain as efficiently as possible, and that is best done with a higher flow rate. Rather than thinking that there won't be enough time for heat to move towards the cool water, and therefore compromising heat loss, it is better to think that there is more fresh water moving onto the CPU and therefore, there is increased cooling.

The reason higher flow rates work better in computer water cooling is this:
There is more water with a larger temperature differential moving through the water block- this removes more heat.
There is more water with a larger temperature differential moving through the radiator- again removing more heat.

This is true even though a system with a lower flow rate will have more time to heat the water in the block and also more time in the radiator to cool the water: since the heat exchange works best with the greatest temperature differential, longer “stay time” is counter-productive.
--------------------------------------------------------------------------------------

Sources of Confusion

There are some variables that have made this more confusing in practice though:
Pump Heat
Type of Flow: Turbulent or Laminar
Friction
Component Flow Resistance
Pump Design

I will attempt to end the confusion on these points next.

Pump Heat:

Pumps generate heat; rather than explain why, let it suffice to say that if you put your hand on a running pump it WILL be warmer than one that is not running.
This heat has to go somewhere: a submerged pump (inside of a reservoir) must add all of the heat it generates to the water; inline pumps are usually designed to use the pumped fluid as a coolant, so most of the heat is going into the water. There will be some amount of heat being conducted to the outer surface of an inline pump, but this should be considered a fairly small amount of the heat produced.

Now, in a simple water cooling system (cpu water block only) we actually have two sources of heat: the cpu and the pump.
Pumps with a higher Flow Rate will generate more heat than pumps with a lesser Flow Rate, and there lies our first bit of confusion:
It is possible to add more heat from a larger pump than will be removed by the higher Flow Rate.

Flow Type:

Water moving through a vessel (tube, block or radiator) meets resistance at the walls; this causes the water at the walls to move more slowly than the water in the center of the tube: this is Laminar Flow.
Laminar flow is bad for heat exchange because the water against the vessel’s walls is slower than the water in the center. Flow rate at the heat exchange surface has diminished.
This is where turbulence comes in - if we can get fluid from the center of the vessel to mix with fluid toward the walls, we end up with more efficient heat removal. Turbulence increases heat transfer significantly over slower Laminar flow.

Turbulent flow occurs naturally in a pipe when the fluid velocity exceeds a certain point, which is dependent on a lot of factors. Also, turbulence isn't an on/off thing - you can have more or less of it. Moving faster will result in more turbulence.
So, in short moving water through the block faster improves heat transfer between the block and the water, which reduces the temperature differential between the block and water required to move an amount of heat.
It is NOT intended to reduce the temperature increase in the water as it travels through the block, but rather to allow more heat to be removed.

Faster flow means more turbulence, and that is a good thing.
--------------------------------------------------------------------------------------

Friction

I am not going to say much on friction here: it generates heat in the pump, and it also generates a minute amount of heat as water flows through system components (a system with greater Head, either Friction or Static, will produce more heat however.)
The main area friction is involved in a water cooling system is in flow resistance- the next area to be covered.
--------------------------------------------------------------------------------------

Component Flow Resistance

Pumping a liquid through a tube creates resistance. The resistance is determined by the cross section of the tube, the length and all fittings in the line.

Static Head (or Lift) - number of feet of elevation that the pump must lift the fluid regardless of flow rate.
.
Friction Head- measure of resistance to flow (backpressure) provided by the pipe and its associated valves, elbows and other system elements:
A smaller tube diameter will have greater resistance: even with identical fittings, pumps and water blocks, a system with larger diameter tubing will have a higher flow rate.
A longer tube will also have greater resistance: even with identical fittings, pumps and water blocks, a system with shorter tubing lengths will have a higher flow rate.
A straight length of tube will have less resistance to flow than one that is bent. A partially kinked tube easily proves this point. Any bend at all introduces some restriction to the flow: a sharper bend is more restrictive than a gradual bend.

I was not able to get data on the most commonly used tubing in water cooling- Tygon, Clearflex and vinyl, but I was able to get data on copper tubing which illustrates the point nicely.
Copper Tubing Flow Resistance by Linear Foot (loss expressed in psi) Conversion: closest I have come to is 1 foot = 1 psi.
Copper Tubing Flow Resistance for Fittings (loss expressed in foot equivalence)
(NOTE that these figures are NOT accurate for the tubing used in most water cooled systems- I include it only to show the relationships between Flow Rate, tube diameter and the use of sharp bends or fittings.)

Head- the entire amount of flow resistance in a system. Static Head + Friction Head = Head
This is what pump head capacity must overcome and is entirely responsible for the reduction of flow rate in a system.
--------------------------------------------------------------------------------------

Pump Design
Positive displacement pumps will maintain constant flowrate but increase pressure as line restrictions interfere.
Most pumps used in water cooling are centrifugal pumps and these are NOT positive displacement pumps.
Getting the pump with the highest flow rating is NOT necessarily the best answer: centrifugal pumps tend to be extremely sensitive to flow restriction.
A pump with a higher Head Capacity will be less sensitive to restriction and be more suitable for computer use.
Which brings us back to the issue of pump heat ;): a pump with more head capacity and higher flow rate will add more heat to the system.
--------------------------------------------------------------------------------------

A Bit about Fans

Just as higher flow rates remove heat from the cpu faster, greater air flow rates through the radiator will improve performance at any given temperature. The actual equations differ since the fluid characteristics- water and air- differ, but the same principles apply.
Similar to a water pump, the pressure needs to be taken into consideration and axial fans don't usually provide a lot of pressure; thicker fans generally will provide more air pressure.
Example: a 120mm fan 38mm thick should be better for our purposes than a 120mm fan 25mm thick.)

The advantage to more airflow is that it provides a good “bang for the buck” improvement in performance; the disadvantage to this is that a fan will create more noise than a water pump, and noise is often one of the areas we are trying to improve with water cooling
--------------------------------------------------------------------------------------

Conclusion

A higher flow rate will give lower temperatures as long as NO other variable is changed.
Heat exchange is improved with turbulence- higher flow rate THROUGH A GIVEN DIAMETER TUBE will flow faster and be more turbulent.
Flow rate can be increased by using larger diameter tubing, the shortest total length of tube possible, fewest bends and fittings possible, lowest restriction radiator possible and by using a pump with a higher head capacity and flow rate.
Maintaining good airflow through the radiator is probably the easiest and noisiest way to improve performance.

Choosing an appropriate pump may be the hardest part: a high head capacity is best, high flow rating important but less so; close attention MUST be paid to the amount of heat generated by a pump as this heat will be added to the system.
--------------------------------------------------------------------------------------



Formulas used by the sources of data below:

Head Loss formula:
Williams and Hazen: Head Loss H= 0.2083(100/C)1.852 * R1.852/D4.8655
Where H=feet of water per 100’, C= Constant for different materials, R=Flowrate (gpm) and D= Inside Diameter. (NOTE: copper is 130. I was unable to find vinyl, Tyron and Clearflex; if anyone knows a verified source for this information, please let me know!)


Q=M x c x Delta T.
There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a constant (the specific heat of water) times the delta T (fluid temp out minus fluid temp in).

Links to source information:

Old Flow Rate Sticky
www.pump.net
www.copper.org/
Google



Much of this information is from the original Flow Rate Sticky and credit is due the original authors.
Thank you for your contributions.

Any inaccuracies are mine ;)
Please PM me with any errors you see and include source information.

EDITED- 3 July 03: added fan pressure consideration to "A Bit about Fans"
 

Zabuzaxsta

n00b
Joined
Jan 19, 2012
Messages
31
Actually with a 1000 lph pump the coolant wouldn't be spending enough time in the water block to absorb very much heat and also wouldn't be spending enough time in the rad's to transfer much heat. Most of the popular pumps today range anywhere from 7 lph to 23 lph with a head height of anywhere from 5 to 9 meters.

Yeah this is the exact same as saying that higher RPM fans are worse because they don't let the air spend enough time in the radiator to absorb very much heat. I mean, that sounds crazy, right? Additionally, that 7-23 lph thing must have been a typo, or at least I hope it was. I could move more liters of water than that in an hour by sucking up the water into a straw and dropping it into another container. 7 lph is slooooooow - that's like a liter every 10 minutes.

Going back to the original point, I'm not quite sure why people think water is so incredibly different from air. Your CPU block is hot, and yes, the quicker you move water through it the less time water is going to have to absorb heat from the block. However, as water is pushed out of the block, fresh, cool water from the reservoir replaces it - THIS IS A GOOD THING. The quicker you can make that happen, the better. Like I said earlier, moving the water slower so it has more time to absorb heat is like saying I want to run my CPU fan slower so the air moves slower and has more time to absorb the heat. I mean, yeah, the air won't absorb much heat at high fan speed before it's pushed out by the fan, but come on...it's getting continuously replaced by fresher, cooler air which is obviously better at cooling your CPU than the air that just got heated up 30 degrees. What's so mystical about water that makes that different?

Thanks for the excellent links, guys...I'll be spending the next few days looking at them. Do I really have to worry about hitting that threshold of heat added from increased flow rate if I stick to a standard, name brand pc watercooling pump? Basically, are there any Liangs or Swiftechs or Koolance pumps I need to watch out for? It seems as though as I long as I get a name brand pump that can deal with the restriction I should be expecting, this whole added heat with increased flow rate isn't a concern.
 

bacon11

Weaksauce
Joined
Jun 24, 2010
Messages
81
Like I said earlier, moving the water slower so it has more time to absorb heat is like saying I want to run my CPU fan slower so the air moves slower and has more time to absorb the heat.

Actually, no, it's not. Double thickness radiators are not twice as effective as a single thickness. Martin from martinsliquidlab tested this and found out that the air at room temp moving through a properly sized (for the heat system) radiator is saturated and cannot absorb any more heat halfway through the radiator. Moving air slower doesn't help, but moving water does to an extent.

The higher flow our pumps get, the more heat they dump into the loop, also proven by martin.
 

W.Feather

Hard DC'er for Aug 2012 / Feb 2019 / Mar 2020
Joined
Nov 10, 2009
Messages
11,478
Depending on the loop, and cooling capacity, the heat put in by the pump is negligible in the whole loop (but still there).

As for pump to look out for, D5 variants are a good one to look out for (though I am still new to WCing)

tangoseal, nice post there, ill have to go through and read it all when i have time, some good info from what i skimmed.

Actually, no, it's not. Double thickness radiators are not twice as effective as a single thickness. Martin from martinsliquidlab tested this and found out that the air at room temp moving through a properly sized (for the heat system) radiator is saturated and cannot absorb any more heat halfway through the radiator. Moving air slower doesn't help, but moving water does to an extent.

The higher flow our pumps get, the more heat they dump into the loop, also proven by martin.
 

bacon11

Weaksauce
Joined
Jun 24, 2010
Messages
81
I know pump heat dump is negligible - I've been telling people that for years when they argue a radiator must go after a pump and before a block - all I was saying was that it is possible to have too much water flow and that having too much flow from our pumps does increase heat dump.
 

Archmage

2[H]4U
Joined
Jul 13, 2000
Messages
3,023
Heh... I intentionally avoided direct address of this flow debate because it always pops up and becomes...a distraction.

That was a good post though, TangoSeal.

I stand by my recommendations.

In a high-heat system with low radiator capacity, pump heat should be a consideration. Having TWO pumps, or a large, powerful pump, probably isn't the best idea in this scenario. I agree that loop order can be ignored in this regard.

It'd be better to run a low-restriction loop with one of the pumps we commonly use already. The cost = lower, performance = same or better, reduced complexity, etc.

That, and 1 pump will provide plenty of flow anyway...
 

skypine27

Gawd
Joined
Apr 18, 2008
Messages
725
Sorry to revive a VERY old thread but...

I built a pretty high end custom loop with modern stuff as my first attempt:





(the tiny air bubbles inside the res are of course gone now, this was after filling the system for the first time before the bubbles bled out over night)



3 x rads. 360mm up top, 420mm in front, and 120mm in rear exhaust port.

Im using the Thermalke D5 Pump/res combo which has 5 speed settings and flow of 1135 L/h at the max speed:
http://www.thermaltakeusa.com/products-model_Specification.aspx?id=C_00002632

I tested temps with the pump running at max speed and with the pump dialed back to position "3". I cant find the flow rate for position 3 but using some basic math if 5 is 1135 then 3 would be approx 680 L/h

There was literally no qualifiable difference between CPU or GPU temps at position 5 vs position 3 (i.e., there was a 1-2 degree C diff but that could also be because of varying room temps).

Position 3 is much better (for me) as with 5.

At speed 5, if I put my hands around the pump base, I could feel vibration and the over all system noise (my case is near silent, all fans are silent low profile models and set to approx 600-800 rpm using Asus Fan Xpert) was due to some almost "whistling" sound of the fluid moving.

At speed 3, the vibration when touching the pump shroud is gone and so is the faint whistling noise.
 

diggi

Weaksauce
Joined
Oct 3, 2012
Messages
110
Nope, Nada, Not True, zilcha, nopers.

Here is a really good write up for you to read:

Credit goes to Rogerdugans at overclockers.com....

Honestly read this, its worth it;s weight!

Does more water flow = better cooling?


I wrote this in an attempt to reduce a large amount of data (which was largely in one very informative thread which was 17 pages long) to one simple and fairly easy to read document.
The original thread is HERE for anyone who wishes to get more in-depth knowledge on this subject.



Heat Transfer

Heat transfer is the basis for ALL computer cooling systems; in water cooled computers we make this more complicated by using multiple heat transfers:
cpu core to water block
water block to water
water to radiator
radiator to air.

*Heat transfer works best with the biggest temp differential: ideal would be cold water to cpu and hot water in the radiator. We cannot achieve this because a closed loop will achieve equilibrium at some point. The principle holds true however- the most efficient transfer happens at the greatest temperature differential, therefore higher flow rates will always help with all other variables remaining the same.
* It is the Heat Transfer that we want to maintain as efficiently as possible, and that is best done with a higher flow rate. Rather than thinking that there won't be enough time for heat to move towards the cool water, and therefore compromising heat loss, it is better to think that there is more fresh water moving onto the CPU and therefore, there is increased cooling.

The reason higher flow rates work better in computer water cooling is this:
There is more water with a larger temperature differential moving through the water block- this removes more heat.
There is more water with a larger temperature differential moving through the radiator- again removing more heat.

This is true even though a system with a lower flow rate will have more time to heat the water in the block and also more time in the radiator to cool the water: since the heat exchange works best with the greatest temperature differential, longer “stay time” is counter-productive.
--------------------------------------------------------------------------------------

Sources of Confusion

There are some variables that have made this more confusing in practice though:
Pump Heat
Type of Flow: Turbulent or Laminar
Friction
Component Flow Resistance
Pump Design

I will attempt to end the confusion on these points next.

Pump Heat:

Pumps generate heat; rather than explain why, let it suffice to say that if you put your hand on a running pump it WILL be warmer than one that is not running.
This heat has to go somewhere: a submerged pump (inside of a reservoir) must add all of the heat it generates to the water; inline pumps are usually designed to use the pumped fluid as a coolant, so most of the heat is going into the water. There will be some amount of heat being conducted to the outer surface of an inline pump, but this should be considered a fairly small amount of the heat produced.

Now, in a simple water cooling system (cpu water block only) we actually have two sources of heat: the cpu and the pump.
Pumps with a higher Flow Rate will generate more heat than pumps with a lesser Flow Rate, and there lies our first bit of confusion:
It is possible to add more heat from a larger pump than will be removed by the higher Flow Rate.

Flow Type:

Water moving through a vessel (tube, block or radiator) meets resistance at the walls; this causes the water at the walls to move more slowly than the water in the center of the tube: this is Laminar Flow.
Laminar flow is bad for heat exchange because the water against the vessel’s walls is slower than the water in the center. Flow rate at the heat exchange surface has diminished.
This is where turbulence comes in - if we can get fluid from the center of the vessel to mix with fluid toward the walls, we end up with more efficient heat removal. Turbulence increases heat transfer significantly over slower Laminar flow.

Turbulent flow occurs naturally in a pipe when the fluid velocity exceeds a certain point, which is dependent on a lot of factors. Also, turbulence isn't an on/off thing - you can have more or less of it. Moving faster will result in more turbulence.
So, in short moving water through the block faster improves heat transfer between the block and the water, which reduces the temperature differential between the block and water required to move an amount of heat.
It is NOT intended to reduce the temperature increase in the water as it travels through the block, but rather to allow more heat to be removed.

Faster flow means more turbulence, and that is a good thing.
--------------------------------------------------------------------------------------

Friction

I am not going to say much on friction here: it generates heat in the pump, and it also generates a minute amount of heat as water flows through system components (a system with greater Head, either Friction or Static, will produce more heat however.)
The main area friction is involved in a water cooling system is in flow resistance- the next area to be covered.
--------------------------------------------------------------------------------------

Component Flow Resistance

Pumping a liquid through a tube creates resistance. The resistance is determined by the cross section of the tube, the length and all fittings in the line.

Static Head (or Lift) - number of feet of elevation that the pump must lift the fluid regardless of flow rate.
.
Friction Head- measure of resistance to flow (backpressure) provided by the pipe and its associated valves, elbows and other system elements:
A smaller tube diameter will have greater resistance: even with identical fittings, pumps and water blocks, a system with larger diameter tubing will have a higher flow rate.
A longer tube will also have greater resistance: even with identical fittings, pumps and water blocks, a system with shorter tubing lengths will have a higher flow rate.
A straight length of tube will have less resistance to flow than one that is bent. A partially kinked tube easily proves this point. Any bend at all introduces some restriction to the flow: a sharper bend is more restrictive than a gradual bend.

I was not able to get data on the most commonly used tubing in water cooling- Tygon, Clearflex and vinyl, but I was able to get data on copper tubing which illustrates the point nicely.
Copper Tubing Flow Resistance by Linear Foot (loss expressed in psi) Conversion: closest I have come to is 1 foot = 1 psi.
Copper Tubing Flow Resistance for Fittings (loss expressed in foot equivalence)
(NOTE that these figures are NOT accurate for the tubing used in most water cooled systems- I include it only to show the relationships between Flow Rate, tube diameter and the use of sharp bends or fittings.)

Head- the entire amount of flow resistance in a system. Static Head + Friction Head = Head
This is what pump head capacity must overcome and is entirely responsible for the reduction of flow rate in a system.
--------------------------------------------------------------------------------------

Pump Design
Positive displacement pumps will maintain constant flowrate but increase pressure as line restrictions interfere.
Most pumps used in water cooling are centrifugal pumps and these are NOT positive displacement pumps.
Getting the pump with the highest flow rating is NOT necessarily the best answer: centrifugal pumps tend to be extremely sensitive to flow restriction.
A pump with a higher Head Capacity will be less sensitive to restriction and be more suitable for computer use.
Which brings us back to the issue of pump heat ;): a pump with more head capacity and higher flow rate will add more heat to the system.
--------------------------------------------------------------------------------------

A Bit about Fans

Just as higher flow rates remove heat from the cpu faster, greater air flow rates through the radiator will improve performance at any given temperature. The actual equations differ since the fluid characteristics- water and air- differ, but the same principles apply.
Similar to a water pump, the pressure needs to be taken into consideration and axial fans don't usually provide a lot of pressure; thicker fans generally will provide more air pressure.
Example: a 120mm fan 38mm thick should be better for our purposes than a 120mm fan 25mm thick.)

The advantage to more airflow is that it provides a good “bang for the buck” improvement in performance; the disadvantage to this is that a fan will create more noise than a water pump, and noise is often one of the areas we are trying to improve with water cooling
--------------------------------------------------------------------------------------

Conclusion

A higher flow rate will give lower temperatures as long as NO other variable is changed.
Heat exchange is improved with turbulence- higher flow rate THROUGH A GIVEN DIAMETER TUBE will flow faster and be more turbulent.
Flow rate can be increased by using larger diameter tubing, the shortest total length of tube possible, fewest bends and fittings possible, lowest restriction radiator possible and by using a pump with a higher head capacity and flow rate.
Maintaining good airflow through the radiator is probably the easiest and noisiest way to improve performance.

Choosing an appropriate pump may be the hardest part: a high head capacity is best, high flow rating important but less so; close attention MUST be paid to the amount of heat generated by a pump as this heat will be added to the system.
--------------------------------------------------------------------------------------



Formulas used by the sources of data below:

Head Loss formula:
Williams and Hazen: Head Loss H= 0.2083(100/C)1.852 * R1.852/D4.8655
Where H=feet of water per 100’, C= Constant for different materials, R=Flowrate (gpm) and D= Inside Diameter. (NOTE: copper is 130. I was unable to find vinyl, Tyron and Clearflex; if anyone knows a verified source for this information, please let me know!)


Q=M x c x Delta T.
There is an elementary equation from basic thermodynamics that states that the rate of heat transfer (Q) equals the mass flow rate (M) times a constant (the specific heat of water) times the delta T (fluid temp out minus fluid temp in).

Links to source information:

Old Flow Rate Sticky
www.pump.net
www.copper.org/
Google



Much of this information is from the original Flow Rate Sticky and credit is due the original authors.
Thank you for your contributions.

Any inaccuracies are mine ;)
Please PM me with any errors you see and include source information.

EDITED- 3 July 03: added fan pressure consideration to "A Bit about Fans"

Good stuff
 

Fire-Fox

n00b
Joined
Apr 27, 2021
Messages
35
I know this is an old thread but i want to ask to tangoseal if my current Custom Loop is built properly or if there is something i should change considering the cooling capacity it has.

Cooling Parts:
Rads
: 2x Hardware Labs Black Ice Nemesis GTX 480 + 1x Hardware Labs Black Ice Nemesis GTX 420
Pump: Eisbecher D5 VPP655PWM
Fans: 10x Corsair LL120 + 3x Corsair LL1140


I did a test: 5.0GHz 1.32V LLC5, 5 hours running Prime95 MinFFT112 - Max FFT112, FFT in place and AVX disabled the temps were this:
Screenshot - 03_04_2021 , 12_31_21.png

When i started the test ambient temp was 26c and the starting water temp was 28c then after a while ambient temp increased to 28c and water increased to 31c till the end of the test.
At idle the water temp is equal or max 2c above ambient temp.

My Build
20210427_144559.jpg
 

Tsumi

[H]F Junkie
Joined
Mar 18, 2010
Messages
13,465
I know this is an old thread but i want to ask to tangoseal if my current Custom Loop is built properly or if there is something i should change considering the cooling capacity it has.

Cooling Parts:
Rads
: 2x Hardware Labs Black Ice Nemesis GTX 480 + 1x Hardware Labs Black Ice Nemesis GTX 420
Pump: Eisbecher D5 VPP655PWM
Fans: 10x Corsair LL120 + 3x Corsair LL1140


I did a test: 5.0GHz 1.32V LLC5, 5 hours running Prime95 MinFFT112 - Max FFT112, FFT in place and AVX disabled the temps were this:
View attachment 351122

When i started the test ambient temp was 26c and the starting water temp was 28c then after a while ambient temp increased to 28c and water increased to 31c till the end of the test.
At idle the water temp is equal or max 2c above ambient temp.

My Build
View attachment 351118

With the deltas you are seeing, there probably isn't much to be done. Your limiting factor is heat transfer from the CPU to the waterblock.

Also, it is better to start a new thread rather than bumping up this old one.
 

Tsumi

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Explain please

At 3 C delta T water to ambient temps, you are considered to be in the excellent category in terms of cooling potential. The reason you are seeing core temps in the 70s is because the heat can't be transferred from the CPU die to the waterblock fast enough at lower CPU temperatures (heat transfer rate increases with higher delta T).
 

Fire-Fox

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At 3 C delta T water to ambient temps, you are considered to be in the excellent category in terms of cooling potential. The reason you are seeing core temps in the 70s is because the heat can't be transferred from the CPU die to the waterblock fast enough at lower CPU temperatures (heat transfer rate increases with higher delta T).
With all that said it means that my Loop is working properly?
 

LukeTbk

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Actually with a 1000 lph pump the coolant wouldn't be spending enough time in the water block to absorb very much heat and also wouldn't be spending enough time in the rad's to transfer much heat. Most of the popular pumps today range anywhere from 7 lpm to 23 lpm with a head height of anywhere from 5 to 9 meters.

EDIT: Sorry, my bust on the flow rate Ya it's 7 to 23 Liters Per Minute not per hour.
Know nothing about this, but my intuition would be that because of regardless of the system you have coolant 100% of time both in the block and in the rad that not a variable that change, the difference become how cold the water is in the block and how hot it is in the rad, i.e. you want to have water cooled by the rad in the block has fast as you can to have the biggest delta of temperature between the water and the block and vice versa in the radiator.

The heat exchange speed depend on the delta of temperature of the coolant, so my first guess would be that you want the water in the block to be there the least amount of time possible so you have always the coolest possible water in it to always have the best possible delta T.
 
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Tsumi

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Know nothing about this, but my intuition would be that because of regardless of the system you have coolant 100% of time both in the block and in the rad that not a variable that change, the difference become how cold the water is in the block and how hot it is in the rad, i.e. you want to have water cooled by the rad in the block has fast as you can to have the biggest delta of temperature between the water and the block and vice versa in the radiator.

The heat exchange speed depend on the delta of temperature of the coolant, so my first guess would be that you want the water in the block to be there the least amount of time possible so you have always the coolest possible water in it to always have the best possible delta T.

In theory, you are correct. In the real world, the difference between inlet and outlet temperature at flow rates above 1 GPM are minimal. If you have a 3 C delta at 1 GPM, that becomes 1.5 C at 2 GPM, 1 C at 3 GPM, and so on.
 

tangoseal

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Wow this thread is old

Fire up a new one. Lets start a fresh discussion. Ill be on tonight to catch up.
 

LukeTbk

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In theory, you are correct. In the real world, the difference between inlet and outlet temperature at flow rates above 1 GPM are minimal. If you have a 3 C delta at 1 GPM, that becomes 1.5 C at 2 GPM, 1 C at 3 GPM, and so on.

I am sure the diminishing return get hit soon enough, but the point stand about not having issue with water not being long enough somewhere.
 

Fire-Fox

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Odd but increasing the pump speed increase the water temp too, the max water temp i have seen when playing games is 31c ( 3c above ambient temp ) but after I've increased the pump speed is hitting 33c that's 6c above ambient, interesting.
 
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MooCow

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I got the Swiftech Dual MCP 355X2 pump and a Hardware labs Blackice Extreme Quad 140mm radiator and this combo is fuckin BEAST. Why two pumps? Because it's safer, you want some redundancy. Also the Dual MCP355X2 has two inlets, so I can fill a loop in a few minutes as the pump literally sucks watercooling solution straight into the loop using Koolance QD3's.

This video is a cold of my system boot using a Blackice Extreme Quad 120mm with four Gentle Typhoons running at 1850rpm each. And then I just upgraded to a Blackice Quad 140mm, same pump. Shed about 4 to 5C cooler compared to the Quad 120mm. Unfortunately it's only cooling a Core i7 7700 non K, and a 2080Ti.




Those Intel 8 to 10 core CPU's are hard to keep cool. I built my friend a 10 core Intel and he had to disable 2 cores just to keep the cache and temps manageable, even after I opened up the EK monoblock and modified the internals to knock off another 6C, it was still hitting the high 80's in the winter running a Quad Blackice 140mm with Noctua industrial fans, dual MCP 355X2, 2080 TITAN, windows open in the winter, and the system was drawing 700+ watts.
 
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Odd but increasing the pump speed increase the water temp too, the max water temp i have seen when playing games is 31c ( 3c above ambient temp ) but after I've increased the pump speed is hitting 33c that's 6c above ambient, interesting.
Try increasing your fan speed.
 

Tsumi

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I am sure the diminishing return get hit soon enough, but the point stand about not having issue with water not being long enough somewhere.

3785 grams of water in 1 gallon. 1 GPM thus becomes equivalent to 63 grams per second. 4.184 joules needed to raise 1 gram of water 1 C. 200 watts is 200 joules per second. 200 / 63 / 4.184 = 0.76. A 200 watt heat source will raise the temperature of the water in a 1 GPM system by 0.76 C as it passes through the block. 400 watts will raise it by 1.5 C, and so on. Doubling the flow rate will halve the amount raised, tripling it will cut it to 1/3, and so on. Note that this is just the amount the temperature changes as it passes through the block, not the equilibrium temperature a cooling system will stabilize to.

Odd but increasing the pump speed increase the water temp too, the max water temp i have seen when playing games is 31c ( 3c above ambient temp ) but after I've increased the pump speed is hitting 33c that's 6c above ambient, interesting.

Where in the loop is your temp sensor?
 

Tsumi

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8x 120mm front fans and 3x 140mm top were at 1300Rpm, 2x rear 120mm at 1500Rpm


Pump

Your water temps rose because the temp sensor is after the radiators and before the heat producing components. The higher pump speed is averaging the temperature through the loop better. Your water temps were probably going from 31-39 (just guessing) before and now 33-36. You might have seen your peak CPU temp drop ~2 C with the higher flow rate.
 

tangoseal

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Odd but increasing the pump speed increase the water temp too, the max water temp i have seen when playing games is 31c ( 3c above ambient temp ) but after I've increased the pump speed is hitting 33c that's 6c above ambient, interesting.

Your water is always going to be higher than amb. The water is always in a higher energy state than the atmosphere outside of the closed system. 6c on a cpu only loop at idle is a little high but is very normal under constant load . You need more pressure through your rad(s).

Watercooling is more about air press over air flow. I personally like a positive pressure case fan setup with the exhaust going only thru the rads.
 
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Fire-Fox

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Your water temps rose because the temp sensor is after the radiators and before the heat producing components. The higher pump speed is averaging the temperature through the loop better. Your water temps were probably going from 31-39 (just guessing) before and now 33-36. You might have seen your peak CPU temp drop ~2 C with the higher flow rate.
So, i had the pump at max speed ( 4800Rpm ) and the max water temp was 33c, now I've decrease the pump speed ( 3200Rpm ) and the max water temp is 31c, my question is: is it better 4800Rpm or 3200Rpm?
Your water is always going to be higher than amb. The water is always in a higher energy state than the atmosphere outside of the closed system. 6c on a cpu only loop at idle is a little high but is very normal under constant load . You need more pressure through your rad(s).

Watercooling is more about air press over air flow. I personally like a positive pressure case fan setup with the exhaust going only thru the rads.
The 6c i was talking about wasn't at idle but under load.
i have 8 intake front and 3 exhaust top + 2 exhaust rear
 

Tsumi

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So, i had the pump at max speed ( 4800Rpm ) and the max water temp was 33c, now I've decrease the pump speed ( 3200Rpm ) and the max water temp is 31c, my question is: is it better 4800Rpm or 3200Rpm?

The 6c i was talking about wasn't at idle but under load.
i have 8 intake front and 3 exhaust top + 2 exhaust rear

Depends on what your goals are. Keeping the system in better equilibrium by having higher flow rates optimizes heat transfer, leading to lower peak temps. The downside is potentially more noise. If the noise level is the same or increased noise doesn't bother you, go with the higher pump speed.
 

LukeTbk

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3785 grams of water in 1 gallon. 1 GPM thus becomes equivalent to 63 grams per second. 4.184 joules needed to raise 1 gram of water 1 C. 200 watts is 200 joules per second. 200 / 63 / 4.184 = 0.76. A 200 watt heat source will raise the temperature of the water in a 1 GPM system by 0.76 C as it passes through the block. 400 watts will raise it by 1.5 C, and so on. Doubling the flow rate will halve the amount raised, tripling it will cut it to 1/3, and so on. Note that this is just the amount the temperature changes as it passes through the block, not the equilibrium temperature a cooling system will stabilize to.
is that a rough estimate that assume that 100% of the heat from source got transferred to the water ? (again restating how little I know about all of this), but from what I remember from my long ago class:
Q = m•C•ΔT

Q the quantity of heat transferred to the water from the block depend on is mass (m), heat capacity of the object they are made of (c) and delta T

The hotter the water get and smaller the difference in temperature between the block and the water get the smaller the heat exchange become, it should not be linear how much the water can rise in temperature if you double the wattage from my understanding (and the reason you want the coolest possible water in your block not one that sit there a while in theory all other things being equal, obviously if it mean a pump that generate more heat in your system or more friction that can be counterproductive pass a point)
 

Tsumi

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is that a rough estimate that assume that 100% of the heat from source got transferred to the water ? (again restating how little I know about all of this), but from what I remember from my long ago class:
Q = m•C•ΔT

Q the quantity of heat transferred to the water from the block depend on is mass (m), heat capacity of the object they are made of (c) and delta T

The hotter the water get and smaller the difference in temperature between the block and the water get the smaller the heat exchange become, it should not be linear how much the water can rise in temperature if you double the wattage from my understanding (and the reason you want the coolest possible water in your block not one that sit there a while in theory all other things being equal, obviously if it mean a pump that generate more heat in your system or more friction that can be counterproductive pass a point)

It is not a rough estimate because heat in = heat out, and the values are all known. The worst case scenario is that your CPU temperature increases by the amount the water temperature rises through the block as you lower the flow rate, but it is usually a lower amount because it's more of an average. Conversely, this also means that at a lower flow rate, the water will be cooled down to a lower temperature on the radiator.

The wrinkle comes on the radiator side. You don't want such a low flow rate that the water cools to near ambient while in the middle of the radiator, diminishing the cooling potential of the radiator. For this reason, having radiators between components is beneficial if flow rates are low. If flow rates are high enough (typically >1 GPM), it doesn't matter because the overall change in water temperature is minimal.
 
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