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General Liquid/Water Cooling Discussion For discussion about Full Cooling System kits, or general cooling topics. Keep specific cooling items like pumps, radiators, etc... in their specific forums.

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Unread 06-23-2004, 03:09 AM   #201
Cathar
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Quote:
Originally Posted by Les
So what is this?
To see if my fumbling theory holds true in practise.
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Unread 06-23-2004, 03:28 AM   #202
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So, we will see some fumbling numbers eventually.
Excellent, look forward to playing with them.
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Unread 06-23-2004, 03:49 AM   #203
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Quote:
Originally Posted by Les
So, we will see some fumbling numbers eventually.
Excellent, look forward to playing with them.
If you're asking for a graph of the relationship between viscosity and performance drop, I don't have one.

With water, the turbulence enhancement appears to offer around a 20% improvement in h over the closest equivalent mathematical model. That 20% is mostly emperically determined.

I roughly predict that the 5x more viscous liquid would roughly reduce that gain over the standard model to around 5-8% above what the standard model would predict for h for that level of viscosity.

Again, not plotted. Am more interested in emperical evidence and formulating rough theory, than attempting to assume that I have a hard theory that works.
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Unread 06-23-2004, 08:30 AM   #204
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Quote:
Originally Posted by Cathar
I roughly predict that the 5x more viscous liquid would roughly reduce that gain over the standard model to around 5-8% above what the standard model would predict for h for that level of viscosity.

Or this is an interpretation of pH's results?
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Unread 06-23-2004, 12:27 PM   #205
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Why not just add 25% glycol to your system and see if the theory holds true. Are you measuring your temps through the socket or the internal cpu sensor?

Edit: I just realized you don't have the block back yet

Last edited by freeloadingbum; 06-23-2004 at 12:34 PM.
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Unread 06-23-2004, 03:02 PM   #206
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Quote:
Originally Posted by Les
Or this is an interpretation of pH's results?
What comes first? The results or the theory?

Am aware of the impact of viscosity. Am unsure of the scale of the impact. Have some thoughts. An uncorrelated data set of 1 (Phaestus's results) is hardly something to form a theory around (unless it involves sticking one's hand in fire). Guesswork at this level Les.
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Unread 06-23-2004, 03:12 PM   #207
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Thanks for the update Cathar. Some interesting developments.

The gains of the G5 vs other blocks will be of great interest.

Thanks for sharing what you can at this time.
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Unread 06-23-2004, 04:33 PM   #208
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Quote:
Originally Posted by Les
An example of the temperature effect on h of as predicted by Sieder-Tate and Flomerics.
Although have not isolated Kinematic Viscosity, this is probably partially responsible.
I think almost totally reponsible Les

From properties here.

Some charts:
Density and Viscosity


Giving Kinematic Viscosity

Quote:
Originally Posted by Cather
If you're asking for a graph of the relationship between viscosity and performance drop, I don't have one.
Well, some fumbling.


(how do you push 4 lpm through a 2mm diameter tube?)

The step from Reynolds number to Nusselt to "h" is fraught. I have no idea of the barrier thickness, no clue how to guess either. Empericality rules. Suffice to say that Nusselt (and thereby "h") is proportional to Reynolds. Ish.

Last edited by Incoherent; 06-23-2004 at 05:00 PM.
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Unread 06-23-2004, 05:11 PM   #209
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Quote:
Originally Posted by Incoherent
......
The step from Reynolds number to Nusselt to "h" is fraught. I have no idea of the barrier thickness, no clue how to guess either. Empericality rules. Suffice to say that Nusselt (and thereby "h") is proportional to Reynolds. Ish.

Think it boils down to the "Ish"
From here, one of my fumbles with "ish"'
Now think "h"s are too high(over estimate of C/W(TIM)) but .....

Some interesting/useful data plotted, will digest.

Last edited by Les; 06-25-2004 at 03:17 AM.
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Unread 06-23-2004, 05:20 PM   #210
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[quote=Les]Think it boils down to the "Ish"
Earlier in this thread(page 4) one of my fumbles with "ish"'
Now think "h"s are too high(over estimate of C/W(TIM)) but .....

[quote]

Unsure of the exact numbers but your curves look like what I'm getting Les. Will check specifics later.

Here are some Nusselt curves,

more proportional to "h" than Re.# is.

Last edited by Incoherent; 06-24-2004 at 02:56 AM. Reason: layout, grammer
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Unread 06-26-2004, 06:34 PM   #211
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Predicted effects of changes in Kinematic Viscosity on h(conv coeff) at constant Density, Conductivity and Heat Capacity.

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Unread 06-26-2004, 07:53 PM   #212
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Quote:
Originally Posted by Les
Predicted effects of changes in Kinematic Viscosity on h(conv coeff) at constant Density, Conductivity and Heat Capacity.
What you've plotted is the basic variation in convectional efficiency with viscosity. What I'm having troubles with solving is what's occuring within the G* blocks before the convectional action. Increased viscosity will definitely be interfering with the longevity of the "turbulation" effects that assist with the block's increased convectional activity.

Have completed re-drawn plans for the G4/G5 which should improve things slightly, and should not be at the expense of "plain water" performance.

Still, it is rather an interesting relationship, and definitely something for people to consider before dumping heaps of glycol in their cooling loops.
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Unread 06-26-2004, 08:46 PM   #213
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Suggest "longevity" is included in the Impingement(Flomerics) calculations.
The Velocities(4.17m/s and 6.67m/s) are those in the nozzle.
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Unread 06-26-2004, 10:11 PM   #214
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Quote:
Originally Posted by Les
Suggest "longevity" is included in the Impingement(Flomerics) calculations.
The Velocities(4.17m/s and 6.67m/s) are those in the nozzle.
Would suggest that Flomerics is attempting to model "classical" jet impingement only.
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Unread 06-26-2004, 11:07 PM   #215
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Yes, it is, also, my understanding is that it is not intended for Submerged Jet Impingement(SJI).
Probably a "fumble to far" to suggest any major "longevity" contribution.
Will wait for your model, when wb's details are released, before further sums.
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Unread 06-27-2004, 01:29 AM   #216
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Quote:
Originally Posted by Les
Yes, it is, also, my understanding is that it is not intended for Submerged Jet Impingement(SJI).
Probably a "fumble to far" to suggest any major "longevity" contribution.
Will wait for your model, when wb's details are released, before further sums.
I think it suffices well enough for SJI, at least in a relative sense. It seems to roughly agree with my experiences, with performance differences for varying jet standoff heights being the notable exceptions.

So yeah, acceptable as a good guidleline for initial starting points.
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Unread 06-28-2004, 03:05 AM   #217
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Quote:
Originally Posted by Cathar
I think it suffices well enough for SJI, at least in a relative sense. It seems to roughly agree with my experiences, with performance differences for varying jet standoff heights being the notable exceptions.

So yeah, acceptable as a good guidleline for initial starting points.

If C/W(TIM) ~ 0.1: yes.
However if C/W(TIM)~ 0.05 , I think I prefer Sieder-Tate( eg Re(3x1mm Entry) from here )
Graphs are still being developed.

Edit: Typo: "C/W(TIM)~0.05" did read "C/W~0.05"

Last edited by Les; 06-28-2004 at 07:03 AM.
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Unread 06-28-2004, 02:05 PM   #218
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I am unsure if this contributes anything to your divagations....
I refer to Incoherent's graph showing relationship between Re and kinematic viscosity. Isn't there an equilibrium between kin. visc. and Re number? If kin visc. decreases then velocity increases and hence Re goes up as well.
Just some idle thinking here, if worthless just ignore and do not reply
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Unread 06-28-2004, 02:36 PM   #219
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Quote:
Originally Posted by Jabo
Isn't there an equilibrium between kin. visc. and Re number? If kin visc. decreases then velocity increases and hence Re goes up as well.
Yes it would. I'm not quite sure what you mean by equalibrium in this case though. More a strengthening I'd say. Or?

Last edited by Incoherent; 06-28-2004 at 05:15 PM. Reason: spelling
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Unread 06-28-2004, 02:47 PM   #220
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Quote:
Originally Posted by Cathar
Still, it is rather an interesting relationship, and definitely something for people to consider before dumping heaps of glycol in their cooling loops.
Also something for the testers/reviewers out there to consider as well. A block could possibly show massivelly improved (CPU-H2O delta T) performance simply by increasing the water temperature.
I'd love to see if there really is a difference. All very well to play with numbers but it's nice to see real life.
(I discovered something else today. Hot water can freeze faster than cold water. An old wives tale that is actually true but not understood.)

Last edited by Incoherent; 06-28-2004 at 05:34 PM.
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Unread 06-28-2004, 03:21 PM   #221
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Quote:
Originally Posted by Incoherent
Also something for the testers/reviewers out there to consider as well. A block could possibly show massivelly improved performance simply by increasing the water temperature.
I'd love to see if there really is a difference. All very well to play with numbers but it's nice to see real life.
(I discovered something else today. Hot water can freeze faster than cold water. An old wives tale that is actually true but not understood.)[/size]
well I was waiting to see if the obvious would be discussed
sure the viscosity changes, and with good instrumentation AND good technique the changed performance is readily apparent
- this suggests an 'optimum' temp (IF the wb has been so designed)

tweek away, are the blind fumbling for the light switch which is not even connected ?

sorry guys, these are numbers for the sake of numbers
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Unread 06-28-2004, 04:22 PM   #222
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I'm just waiting for my blocks to get back to me...
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Unread 06-28-2004, 05:15 PM   #223
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Quote:
Originally Posted by unregistered
tweek away, are the blind fumbling for the light switch which is not even connected ?

sorry guys, these are numbers for the sake of numbers
Well, numbers are interesting, and are quite illuminating themselves. The temperature/viscosity relationship is moot however, since our end goal is (normally) lowest load temperature, not highest convectional efficiency. I think 'optimum' coolant temperature within the bounds of reality is as cold as possible.
The viscosity in itself however, is highly relevant.

Last edited by Incoherent; 06-28-2004 at 05:23 PM. Reason: Further thoughts
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Unread 06-28-2004, 05:19 PM   #224
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Quote:
Originally Posted by unregistered
sorry guys, these are numbers for the sake of numbers
Not "numbers for the sake of numbers".
Numbers were used in the design:
Quote:
Originally Posted by Cathar
I had pretty much designed around kinematic viscosities typical of water/alcohol, but a 25% glycol mix is around 5x more viscous than water, and I strongly suspect that this is causing an issue.
Playing with a performance number(h(con coeff)) and kinematic viscosity
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Unread 06-28-2004, 05:28 PM   #225
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I think I understand what is being played with,
but when the desired/reasonable result is arrived at via fiddling with the factor of interest; . . . . .

ignore my skepticism, it is not new news on this topic - (h
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