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pHaestus
02-02-2004, 08:01 PM
It was initially my goal to estimate CPU wattage by using the following formula:

(Flow Rate*delta T (waterblock outlet - water inlet) *4186)/60

With flow rate in lpm and water temperatures in C

Presumably this should result in a constant value for W over flow rate tests as CPU MHz and Voltage are unchanged. What you actually get though looks like this:

http://phaestus.procooling.com/temp/WEst/deltatwbcomp_s.jpg (http://phaestus.procooling.com/temp/WEst/deltatwbcomp.jpg)

Good agreement from block to block for the temperature rise across the wb; this is encouraging. Some difference doesn't surprise me much because the 3 barb blocks are harder to insulate than the 2 barb blocks. Look what happens when you use the above equation to calculate W:

http://phaestus.procooling.com/temp/WEst/west_s.jpg (http://phaestus.procooling.com/temp/WEst/west.jpg)

Les and I have talked about this a bit in the past and are operating under the theory that as flow rate increases, C/W goes down, and wb efficiency (the percentage of the CPUs heat that goes through primary cooling path) goes up.

Anyway the big shift in W estimated by the equation is the reason that I haven't been using C/W for wb tests. Any advice on how to test/think about/explain these results would be most appreciated.

And for the calculation-minded, here is a spreadsheet (http://phaestus.procooling.com/temp/WEst/flowratedata(uncorr_for_average).xls)

Caveat: The DeltaT (CPU-wb in) from these tests were adjusted down to the average value at 1.50GPM for the review I just published.

jaydee
02-02-2004, 08:43 PM
I think your problem is secondary heat loss through the bottom of the CPU, the socket itself, and the pins. The more efficient the block is the less the above secondary losses will happen because there is less heat to escape. The worst the block performs the more heat to go out the secondary paths. I think it would be near impossible to get a solid CW without completely insulating the Socket. Which is probably impossible. You maybe surprised (or maybe not) how much heat flows through the pins and escapes through the traces and the PCB.

Also another notion, if the CPU is cooler it generally runs more efficiently and thus uses less wattage to achieve the same goal. Hummm, I might off on this on second thought.

A combination of the above is possibly the problem.

Thats the best I can come up with. I can be way off base but it sounds good to me right at this minute. :D

rocketmanx
02-02-2004, 10:07 PM
Looking at C/W plots for various water blocks it appears to me that the blocks efficienecy doesn't go up linearly. As flow rate increases C/W looks to level off.
At the same time the delta T of the air and various block parts that jaydee mentioned is going up. So the parts that are losing heat are adding more and more to the loss.
This would seem to make sense looking at the RBX. It has the most surface area of all the blocks where heat would be lost.

Seems, like jaydee said, a compound problem.
Who knows though I may be reading you're chart all wrong :D

UNDERBYTE
02-02-2004, 10:23 PM
1.) Water in is increasing in temp so the radiator is not dissapating the heat eff. at increased flow?

2.) As to the secondary heat paths - cpu is around 30 C. what is the motherboard temp from local components 50-55C?

if anything the heat flow from secondary sources would be from + to - to the block rather than from..??

Just a thought

jaydee
02-02-2004, 10:28 PM
1.) Water in is increasing in temp so the radiator is not dissapating the heat eff. at increased flow?

2.) As to the secondary heat paths - cpu is around 30 C. what is the motherboard temp from local components 50-55C?

if anything the heat flow from secondary sources would be from + to - to the block rather than from..??

Just a thought
Your #1 is irrelevant as he uses a chiller to control the water temp. That is why I think it is in the secondary heat losses. And as rocketman pointed out the mass of the block may add an extra level of secondary heat loss confusion.

Have to ponder you #2 point another time. I am way to tired at the moment to think.

UNDERBYTE
02-02-2004, 10:44 PM
Point # 2 is not complicated - all heat is on a gradient if the block / CPU is cooler than the Local components / mother board , the heat is only going to go one way.

Most thermal analysis alla` intel assume that the air cooled CPU is at 60C and the board at 50C hence secondary heat paths.

you water cooled guys are way cool - different ball game it is just the opposite

jaydee
02-02-2004, 10:53 PM
Point # 2 is not complicated - all heat is on a gradient if the block / CPU is cooler than the Local components / mother board , the heat is only going to go one way.

Most thermal analysis alla` intel assume that the air cooled CPU is at 60C and the board at 50C hence secondary heat paths.

you water cooled guys are way cool - different ball game it is just the opposite
Yeah I am just having a hard time adding that into the C/W confusion. The components, I wouldn't think, would run much cooler or warmer per block being the load is somewhat consistant. Seems it would zero itself out. Unless if the CPU was running cooler and more efficent it might make those parts run cooler aswell and add less heat. Thats interesting. If the block has a bigger mass or is wider, it might pick up more heat from those parts. Like the RBX though that is narrower it may be shielded more from those hot parts....

If this is the case then changing mobos out may contaminate the tests being those parts are closer or farther apart depending on the board.... Not what pH wants to hear. :D

BAH, to much thinking. I am beyond tired. It was a long day at work today...

Les
02-02-2004, 11:40 PM
Morning and thanks for Excel..
Started to play thinking on lines of 2ndary paths and dP*Q - ala Tecumseh (http://www.ocforums.com/showthread.php?s=&threadid=142956).
Dunno but initially trying 1/dTwb v Q plot http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh.jpg
Unfortunately my Excel97 seems to play weird games with "DTek and Maze4" data in your Excel(2000?) - copy and Paste Special. Will take a little time to sort.

My first impressions of results "Oh God. Why did I ask".Think "Confusing data" may be an understatement.

Les
02-03-2004, 09:46 AM
Spent a morning playing
Am no wiser than at end of Incoherent's thread (http://forums.procooling.com/vbb/showthread.php?t=8433)
Dunno from where the Watts are coming
Maybe Incoherent's technique would reveal if caused by measurement errors.
Will have another look at his data. However the number of variables makes analysis a nightmare.
Possibly he could be persuaded to do some further work with fewer variables.

EDIT. The mandatory graph:
http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh1.jpg
Have used "CPU diode raw" to calculate "C/W" in this instance. "CPU diode raw" is the diode temp associated with the dTwb measurement?

UNDERBYTE
02-03-2004, 11:59 AM
if the CPU was running cooler and more efficent it might make those parts run cooler aswell and add less heat. Thats interesting. If the block has a bigger mass or is wider, it might pick up more heat from those parts. Like the RBX though that is narrower it may be shielded more from those hot parts....

If this is the case then changing mobos out may contaminate the tests being those parts are closer or farther apart depending on the board.... Not what pH wants to hear. :D

BAH, to much thinking. I am beyond tired. It was a long day at work today...

The chiller is a reliable constant and so is the internal diode. This just leaves the MOBO and blocks as variables

In electronics cooling mag (JEDDC)precision testing usually involves encapsulating device front and back (circut card or mobo) with a water cooled setup to filter out the thermal noise.

In another set up they use copper wings/heat sinks attached to the mobo/card and set up on an islolated stand in a wind tunnel to cool the board to ambient for the same purpose as the water to filter thermal noise.

For simplicity's sakeI am an advocate of the bill adams test block - Watts in/ watts out with good degree of Accuracy. and you are not trying to extrapolate what all the test data means. Then use that as a baseline for "real world testing" and see if results hold up

After All what you really want to know is which configuration is better or worse right? Test block will tell you that. Otherwise unless test setup is more refined the best guess is just that, a guess.

KnightElite
02-03-2004, 12:42 PM
Actually, there is no chiller at the moment. Just a radiator.

BillA
02-03-2004, 01:17 PM
do not be mislead by data not understood

the thermal resistance of a device is independent of the applied load
period - full stop
(except I am now testing a device which is NOT !?!)
EDIT: and will, of course, decrease with an increase in the flow rate (sorry Les)

with sufficient accuracy one will 'see' some non-linearity, but this is related also to secondary losses
- large heat dies are 'bad' due to the increased difficulty of insulating them (including the upper surface)
- and CPU heat sources are vastly more difficult (try placing some TCs in the gap behind the mobo, then ck the uniformity of these temps between one test series and another)

"Les and I have talked about this a bit in the past and are operating under the theory that as flow rate increases, C/W goes down, and wb efficiency (the percentage of the CPUs heat that goes through primary cooling path) goes up."

EDIT: deleted a bunch of confused junk

so what is the latest on the chiller saga ?

Les
02-03-2004, 04:23 PM
"Les and I have talked about this a bit in the past and are operating under the theory that as flow rate increases, C/W goes down, and wb efficiency (the percentage of the CPUs heat that goes through primary cooling path) goes up."

the above is ok if you delete "C/W goes down", but is an apparent increase of ~50% appropriate over the flow range tested ?
seems a bit much, no ?

See no reason to delete "C/W goes down".
Otherwise, as indicated previously (http://forums.procooling.com/vbb/showthread.php?t=8433&page=4&pp=25) , agree

jaydee
02-03-2004, 08:04 PM
so what is the latest on the chiller saga ?
I thought he was using a chiller. Guess I will re-read the article again... :shrug:

pHaestus
02-03-2004, 09:31 PM
re: Chiller:

Still completely up in the air. UPS will only deal with the shipper, who in this case is considered to be the Hamilton ON Mailboxes Etc.

jaydee
02-03-2004, 09:39 PM
re: Chiller:

Still completely up in the air. UPS will only deal with the shipper, who in this case is considered to be the Hamilton ON Mailboxes Etc.
Doh!


Another thought, you did changve mobo's in the middle of testing these blocks right? Would it be wrong to think a different mobo has different voltage regulation and may add or subtract a few volts changing the watt output? I know every different mobo I have reads a different voltage even if i use the same power supply on all of them.

pHaestus
02-03-2004, 09:45 PM
Changes in voltage should translate to changes in the DeltaT (CPU-water in). No statistically significant change was noted (I changed after running 5 reps of the DTek Whitewater). I also reran the RBX and the performance fell right at the average value of the earlier run. MBM reports same idle and load voltage as well.

This was something I was concerned with though; that's why I reran those blocks

jaydee
02-03-2004, 09:48 PM
Changes in voltage should translate to changes in the DeltaT (CPU-water in). No statistically significant change was noted (I changed after running 5 reps of the DTek Whitewater). I also reran the RBX and the performance fell right at the average value of the earlier run. MBM reports same idle and load voltage as well.

This was something I was concerned with though; that's why I reran those blocks
And with that I will have to bow out and sit on the sidelines. If it isn't something mentioned above I just don't know. :shrug: Over my head....

bigben2k
02-04-2004, 09:33 AM
Assuming that the thermal interface has a fixed C/W, the dT readings wouldn't be affected by it, under the same power.

Given that the readings indicate a max power to be ~110 W, is the CPU in a position to give out such power?

pHaestus
02-04-2004, 09:39 AM
Well...

The delta T seems reliable enough (the wb in and out probes report the same number when placed in water together) and the flow rate is also imo pretty reliable (I installed the swissflow flowmeter in that loop "just to see" and it was within 0.01GPM of the GPI). The equation is good, so that wattage MUST be put into the water by the CPU. But how much of that observed W is coming from northbridge/ram/mobo power elements through traces and up into CPU?

No ideas here; need perhaps W estimates vs coolant temperature?

KnightElite
02-04-2004, 10:35 AM
I doubt you've got much additional heat coming into the CPU from the other components... as you know heat propagates from warmer areas to cooler areas. It seems much more likely that as the flow increases, and the waterblock cools better, secondary cooling paths (through the pins and the motherboard, etc...) become less important, because of the higher delta-T between the block and the CPU die.

Also, all the other components should be generating a constant quantity of heat, given that their cooling is not changing at all during the entire process.

prandtl
02-04-2004, 11:28 AM
I doubt you've got much additional heat coming into the CPU from the other components... as you know heat propagates from warmer areas to cooler areas.
I remember I read somewhere (cant remember if it is Anandtech.com or hardware.fr) that the mobo voltage regulators can get very hot (in the 90ish C) and pHaetus already stated that the nb was passively cooled and was running hot too (hotter than the cpu to my understanding). As you say, heat goes from warmer to cooler... ie (nb, volt reg) - Q -> (cpu)

freeloadingbum
02-04-2004, 05:48 PM
I would have expected cpu wattage to be fairly consistant with cpu temp across all the blocks but that is not the case. The maze 4 is over 35 watts higher than the cascade at near the same ( the maze is still warmer) cpu temp, the maze 4 at 2.5gpm compared to the cascade at .5gpm. Why is that? I would try retesting without the insulation and see if that's the problem.

I would consider swaping the sensors with each other and see if you get the same results. You could also try running the test at all the flow rates with the computer off and see how the sensors are affected. I would think at some point you would start to see some heat from flow friction within high pressure blocks like the cascade.

Another possible problem may be a difference in temperature gradient across the flow through the half inch tube. High pressure blocks may mix the water better than low pressure blocks giving the output sensor different readings for the same wattage (though I think this is extremely unlikely).

In the end you may never be able to separate cpu wattage from secondary losses or gains but I think it would be interesting to find out why blocks vary so much at the same cpu temp.

lolito_fr
02-05-2004, 02:37 AM
I was also thinking of heat produced in the block due to friction, and conversion of potential energy into heat. For the Cascade, 2.5m @ 7.5lpm turns out to be roughly 3W unless I'm missing anything? Not entirely negligeable, but not even close to 25W. Plus this would be a quadratic variation, rather than the quasi-linear one that we're observing.

I find it hard to believe that secondary losses could amount to 25% variation in total power dissipation, considering that the sink temperature is apparently not varying by more than 0.5°C, and even the core is only changing by 2°C. (Cascade data)
Nothing can be that closely coupled to the waterblock for such a small change in temperature to produce such a large increase in power?

Non uniform mixing of flow, or sensor temps influenced by pipe surface temps seems like a good possibility.
Also PH, what are the specs for the flow meter?
(How much do you trust it…?)

freeloadingbum
02-05-2004, 04:22 AM
For the Cascade, 2.5m @ 7.5lpm turns out to be roughly 3W

I've googled for hours trying to find a formula to calculate wattage based on pressure and flow but came up empty handed. Could you share yours with me? Thanks in advance.

I wonder how much of a performance enhancement you would get from mounting a fan in back of the motherboard, considering how much of an issue secondary heat seems to be.

Les
02-05-2004, 05:22 AM
[QUOTE=lolito_fr]
1)I was also thinking of heat produced in the block due to friction, and conversion of potential energy into heat. For the Cascade, 2.5m @ 7.5lpm turns out to be roughly 3W unless I'm missing anything? Not entirely negligeable, but not even close to 25W. Plus this would be a quadratic variation, rather than the quasi-linear one that we're observing.

2) I find it hard to believe that secondary losses could amount to 25% variation in total power dissipation, considering that the sink temperature is apparently not varying by more than 0.5°C, and even the core is only changing by 2°C. (Cascade data)
Nothing can be that closely coupled to the waterblock for such a small change in temperature to produce such a large increase in power?

3) Non uniform mixing of flow, or sensor temps influenced by pipe surface temps seems like a good possibility.

(QUOTE]

1) Your sums are correct ,3 watt is about right: Using Watts ~ m(H2O)*LPM/6

2) Just dunno. Simple modelling is nigh impossible with the complexity of the thermal enviroment.May be possible to split losses/gains into the component which enters/leaves the system through mb/die path and that through Non-die/wb path. The former being possibly only "C/W" dependant and the latter being "Flow-rate and wb" design dependant.Just possibly,this is evident in the "watt v C/W" plot.Some attempt to split these is in Incoherent's work (http://forums.procooling.com/vbb/showthread.php?t=8433).
However consider it to be extreme speculation and not worth pursuing until thoughts are more crystallised

3) Again dunno,but would have thought Bill(in his "'Heat Source Efficacy' measurements) would have encountered this problem if it exists.

lolito_fr
02-05-2004, 05:26 AM
A little physics.
Pressure is just potential energy.
So to pump 7.5litres of water up to 2.5m, you need m*g*h Joules of energy.
m=mass in kg (or volume in litres, as 1litre of water=1kg)
g=9.8m/s^2
h=height in meters
7.5*9.8*2.5=184J

If you pump 7.5 litres in one minute, that’s 184J/minute.
Divide by 60 to get J/s:
184/60=3.07J/s=3.07W

Derived formula: P=0.16Q.H
P in Watts
Q in lpm
H in m

lolito_fr
02-05-2004, 05:32 AM
sorry! Les beat me to it.

Les
02-05-2004, 05:57 AM
sorry! Les beat me to it.

No need for apology.
I only gave the result, not the derivation.
It is the derivation which is important.

Myth
02-05-2004, 06:59 AM
I know it's probably me who doesn't understand the goal of this exercice, but wouldn't calculation cpu wattage be easier and more reliable using a formula based on Vcore and cpu specs ?

murray13
02-05-2004, 09:26 AM
This whole thing about being able to calculate CPU wattage using flow rate and delta T sounds fishy to me. All you are measuring is how much power (thermal) is being transfered to the water. Not the power output of the CPU. What you are seeing must be secondary heat loss.

There could also be problems with the equation.

Incoherent
02-05-2004, 09:29 AM
pHaestus, a very small offset in one of your water temp probes could give this result (the strange increase in power as flowrate increases).
I am talking about an offset of perhaps less than 0.05 degrees.
A simple way to test this would be to reverse the flow though the waterblock you have in your setup now, so that inlet T becomes outlet T and vice versa. The block performance would of course suffer but, if there is in fact an offset, we could work out the exact amount. If you can find the time to take many measurements at a few flowrates I think that this would be rather valuable. I am not questioning your setup (your data shows that it is actually stunningly accurate, the noise is unbelievably low) but an offset between the thermistors might be very small and difficult to detect.
If you have been interchanging inlet T and outlet T then this is of course irrelevant. It proves that the setup is excruciatingly accurate.

Cheers

Incoherent

BillA
02-05-2004, 09:47 AM
I'm suspecting 'h' needs to be addressed

Incoherent
02-05-2004, 10:02 AM
I'm suspecting 'h' needs to be addressed
"h"?
I am guessing "head loss"? or "heat capacity"? Sorry Bill, you are losing me.
(not too difficult :))

Cheers

Incoherent

BillA
02-05-2004, 10:13 AM
'h', as in convection coefficient
in pHaestus' graph #2 the 'apparent' wattage goes from low to high along with the flow rate
- one would observe that the value of 'h' is also going from low to high (relatively speaking)

I'm guessing the equation has been simplified a bit much
no answers here, just a suspicion

pHaestus
02-05-2004, 10:31 AM
I'll see about just swapping the thermistors tonight incoherent

Bill: Did you get my e-mail re the MCW5000-A springs?

BillA
02-05-2004, 11:05 AM
yea, sorry, washers not needed

Myth
02-05-2004, 04:58 PM
I Still don't get what it is the result is supposed to be, C/W of the system is easy to calculate using other much easier to get values. This program can help do i very easy, I know the page is in Danish, but just press Download and the program is in english.

http://www.overclocking.dk/download.asp?mode=show&id=324

pHaestus
02-05-2004, 06:42 PM
GIGO, Myth

Myth
02-05-2004, 06:58 PM
Damn hopefully beeing Danish can excuse my poor english.. GIGO? don't understand.. ( I know i prob. misunderstood the topic of this discussion.. but i thought he wanted to calculate the C/W of his system..)

freeloadingbum
02-05-2004, 07:10 PM
The more I think about it, the more I'm convinced that temp gradient in the hose is responsible for the large difference in wattage between the cascade and maze4 at the same cpu temp. The flow through the outer 2 channels on each side of the maze are problably picking up little or no heat while the center channel may be picking up 50% or more. The cascade with all the flow starting at the core combined with the high turbulence should definitely see a better mixing than the maze.

If the above is true then changing the depth of the sensor ( if possible) would yield a large change in the maze wattage (50 watts perhaps), while yielding a small change in the cascade (0 to 10watts)

If this also proves true, then blocking off the flow to the maze's outer channels (filling in with silicone for instance) should give a nice performance boost by increasing the velocity of the inner channels for the same flow rate. I'm guessing as high as 1.5C at 1 gpm.

Edit: spelling

pHaestus
02-05-2004, 07:31 PM
GIGO is an old programmer acronym. Short for Garbage In, Garbage Out. Those CPU Watt calculators aren't grounded in reality. Sure I can calculate a C/W, but it'll be crap.

Les
02-05-2004, 08:37 PM
pHaestus
Were the tests performed with the TBredB 1700+ at 2200MHz and 1.85V ?
Don't think MHz and V were specified in article.
Info would be useful for cross-ref to Incoherent's thread.

BTW Benchtest com Calculator (http://www.benchtest.com/calc.html) indicates 113Watts (100% usage) for a TBred 1700+ at 2200MHz and 1.85V.

Aardil
02-05-2004, 09:34 PM
Beginning to wonder if splitting atoms wouldnt be easier :shrug:
A great thread just wish I understood what all them pretty lines ment.

Myth
02-06-2004, 05:00 AM
#42 Ahh!

I know the eventhough we have spent a lot of time geting the calculations i the program as correct as can be.. it will always be more of a theretical result than a real life one, and it we do get similar results compared to the BTW benchtest calculator. So we prob. use the same formulas. The question realy is how far the result calculated this way is from the real life result which he is trying to calculate using the formula..

But i get your point, and think i will wait and see if we get some workable formulaes, and perhaps they could be added to the program..

Incoherent
02-06-2004, 09:43 AM
An observation pHaestus

If you are using anti-freeze in your system, the value for heat capacity should be less than 4186J/kg*°C. Unfortunately I don't know how much but I would guess that it would be in the region of 10% less with the 1:4 mix you are using. Not particularly significant when comparing waterblocks but something to remember if we want to compare data from different power measurement techniques. It does bring your W results down to a perhaps more realistic level but doesn't explain the slope.
Again, I suspect an offset. A bit of qualification for this statement in these two charts.
http://w1.863.telia.com/~u86303493/Computer/phaestus/chart_deltat_offset.jpg
This a bit colourful maybe but it is showing the calculated delta T curves vs flowrate for various power levels. Also shown are the Ts from your data for all the blocks. As you can see the delta T's adjusted by an offset of -0.07 deg fit very closely to a 70W heat source.
http://w1.863.telia.com/~u86303493/Computer/phaestus/chart_watts_offset.jpg
The second chart shows the new power calculation vs flow rate. This is a bit ideal but might point in the direction of a (small) probe error.

Another thing, I think that pressure loss needs to be measured for these blocks at different flowrates. I think that presented as it is the Cascade seems to be massively ahead of the competion (a conclusion I believe is not incorrect) but for a given pump/system the flow will be less through the Cascade, and hence the performance delta will not be as much as you'd conclude from simply looking at flow rate. I think this has been discussed elsewhere.
Not to take ANYTHING away from your review/testing methods mind you, or from the Cascade. Both are fantastic.

Cheers

Incoherent

Les
02-06-2004, 10:17 AM
Incoherent
You have been busy.
Good thinking. Never thought of introducing a known error.
I use Scott Gamble's data (http://www.overclockers.com/articles609/index03.asp) for anti-freeze correction.
Yep 10% seems about right.
Graphs look eminently sensible. Will check your Excel manipulations for stupidity - will only post if find.

Incoherent
02-06-2004, 10:23 AM
Will check your Excel manipulations for stupidity - will only post if find.
Be my guest Les. Excel sheet is here (http://w1.863.telia.com/~u86303493/Computer/phaestus/)

Cheers

Incoherent

Les
02-06-2004, 10:28 AM
Using pH's but will cross-check.
Thanks.

pHaestus
02-06-2004, 11:17 AM
Incoherent you are 100% right about needing pressure drop vs. flow rate data. My digital pressure gauge was acting strangely when I was testing that MCWChill; I can see if maybe it was the low temperatures that were messing it up and if so generate. Otherwise I bid on ebay periodically but haven't yet gotten lucky.

I took the day off today and just went downstairs to look at the test system. The pump is running but the PC isn't on. There is a deltaT of 0.06C across the Maze4 wb at 1.5GPM; raising the flow rate to ~3gpm raises the delta T to 0.07C. Guess I'll swap the inlet and outlet and see if that offset persists (in the opposite direction); if so I'll just go back and adjust the outlet temps by the appropriate amounts. Winder where that came from; I specifically remember putting both these probes into water and they read exactly the same as water temp changed...

pHaestus
02-06-2004, 11:22 AM
As my above post seems to be a bit TOO fortuitous I thought I'd snap a pic:

http://phaestus.procooling.com/nopcdeltat.jpg

BillA
02-06-2004, 12:04 PM
you should expect a diff when flowing
the question is at zero flow rate
one would suspect that the origin will not be attainable
- but this is not the principle cause of the Wattage discrepancy

everything has been on a couple of hours beforehand, eh ?
(between the Flukes and astd dmms 2 hrs is the minimum warmup time for me)

Les
02-06-2004, 12:26 PM
you should expect a diff when flowing.....
...



Perhaps 0.00045 C for the Maze4 at 1.5gpm ( 5.68lpm,0.19mH2O extrap JoeC, using W=lpm*m(H2O)/6=0.18watt)?

Edit. The graph:
http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh2.jpg

Diff between dT @1.5gpm and 3gpm is ~ 0.0013 C

Incoherent
02-06-2004, 05:43 PM
As my above post seems to be a bit TOO fortuitous I thought I'd snap a pic:

http://phaestus.procooling.com/nopcdeltat.jpg

Hmm.

I figured about 0.0649C. I guess math matches reality once in a while. Cool.
Better verify that the lower thermometer is the outlet T? The offset I see is negative.

A table of the offset vs flow rate with no heat load would give us a calibration.

Happy.

Cheers

Incoherent

BillA
02-06-2004, 06:07 PM
on the topic of: Some Interesting/Confusing Data from testing

http://thermal-management-testing.com/vert-horiz.gif

recognize it ?
gonna add whole new complexities to testing our little toys

freeloadingbum
02-06-2004, 06:46 PM
Is 24.71 the water temp you test with? The offset might be a little different at 28C for instance.

pHaestus
02-06-2004, 08:53 PM
I generally test around 19-20C; the pump imparts a substantial amount of heat into the water, and when the fans on my radiator aren't running this can warm the water up a fair amount. I just swapped the probes (put the inlet probe into the outlet probe's fitting and vice versa) and now the top reading is a little higher. I'll let it return to equilibrium and then check it in an hour or two. I'll replace the probes as they were for all of the earlier wb testing and see if I can't generate an offset vs flow rate curve for you guys tonight too.

This is actually a VERY good thing; I can deal with a little offset in my thermistors a hell of a lot easier than I can more fundamental problems with the experiment (like large secondary heat inputs from mobo traces).

pHaestus
02-06-2004, 08:55 PM
Bill ummm trying to guess what could give you such a curve... Heat pipe of some sort??

pHaestus
02-06-2004, 11:13 PM
OK I am officially dumb. I spent about 30 minutes looking at my test system this evening and FINALLY realized that the probes aren't all configured the same way that they used to be. When I replumbed everything to get the wb inlet and outlet probes closer to the waterblock, I must have moved one of the matched set of thermistors around because that probe is now between the pump outlet and the radiator inlet. I have a fourth probe that wasn't in use that is brand new. It reads 0.02C higher than the probe I have in the inlet. What I'll do tonight is run a flow test with and without PC running. This will give me the offset over the whole range and should be able to verify that this was the problem with the earlier data.

I am JUST smart enough to be dangerous

pHaestus
02-07-2004, 01:29 AM
Ok makes sense now and looks sensible. Here's W estimates from flow rate and delta t across waterblock (adjusted 0.02C to account for difference in probe without PC running):

http://phaestus.procooling.com/revisions/wattsest.jpg


Block used in today's testing is the Swiftech MCW5000-A; deltaT CPU-wb in looks like this:

http://phaestus.procooling.com/revisions/deltat.jpg

If you take the average watts from top graph (73.14W) then you can estimate a C/W:

http://phaestus.procooling.com/revisions/cw.jpg

All becomes clear now (and more test data as f(MHz and VCore shall be collected over the weekend)

lolito_fr
02-07-2004, 09:25 AM
I'm impressed. Wish I'd come up with that solution, Incoherent:) (definitely a misnomer)
Looking forward to more graphs…including P/Q!

BillA
02-07-2004, 10:51 AM
Bill ummm trying to guess what could give you such a curve... Heat pipe of some sort??
give that man a chocolate ceegar
yup

bigben2k
02-07-2004, 11:40 AM
on the topic of: Some Interesting/Confusing Data from testing

http://thermal-management-testing.com/vert-horiz.gif

recognize it ?
gonna add whole new complexities to testing our little toys
Nice work pHaestus!

Not to put a damper on your success, but to what do you attribute the variation on the CPU power (I have a fair idea, I'd just like to hear your version, and I think a lot of people would be interested).


Bill, before I wander off thinking about this graph for two or three weeks, then bring it back up again (!), is there anything else that you can share about it?

pHaestus
02-07-2004, 11:57 AM
The variation in power from last night/this am's data? At very low flow rates it's difficult to perfectly insulate the hoses and I suspect that the 0.5GPM flow number is somewhat suspect for that reason. For the numbers above 2GPM the delta T is so small that better resolution than 0.01C is required (a difference of 0.01C corresponds to nearly 10W). The numbers from 0.75-2GPM are pretty much dead even at 72-74W; not much variation of CPU power with flow in that case.

If you mean the earlier test results then there was a 0.06-0.07C offset in my temperature probes that I didn't catch (but incoherent did).

As for Bill's graph, consider that we are dealing with water inside a heat pipe, and that water has some interesting properties which occur near phase transitions. Solid water floats, for instance.

pHaestus
02-07-2004, 12:08 PM
Bill a question about your heatpipe:

If you go low enough in power applied do you see a flat C/W vs power region? I'd expect that you'd hit a point where there isn't enough heat to cause a phase change in the pipe. Then if you keep boosting power over the heatpipe's working range far enough does it return back to that same flat line? Where you just add so much more heat into the system that the heatpipe doesn't work because the cold side is too hot?

I am visualizing a situation where at really low and really high power (temperatures completely outside the heatpipe's operating range) that you get performance that is pretty similar to just the heatsink alone, and that only within mfgr specs is there a big improvement by adding a heat pipe.

I have never personally used a heat pipe though so I could be way off base about how they supplement convective cooling...

BillA
02-07-2004, 12:09 PM
pHaestus identified it, a heat pipe
why the curves are the way they are is pretty obvious upon reflection
- not so obvious is the 4 days of testing (at 12 hrs/day, eh) to obtain repeatable results, and my initial disinclination to believe what I was seeing

pHaestus' results and his quandary expressed in this thread are a typical 'obstruction' encountered in this type of thermal testing, the smallest oversight can consume huge amounts of effort to identify the discrepant element
- this is not a criticism, pHaestus will do this many times more until he follows a written setup procedure - and establishes his own means of 'zeroing' the test bench prior to the collection of data
-> if the first data point does not replicate something already known there is always the potential to be heading off on a wild goose chase

take the time to ck everything out first
look at the Digitec photos, see those colored dots on the thermistor connectors and the face plates ?
(that was part of a setup control system)

pHaestus
02-07-2004, 12:22 PM
Bill's exactly right; wild goose chase fairly accurately describes this thread. I feel bad about wasting lots of Les's and incoherent's time because I had a problem with my data collection. On the other hand I have learned a good lesson, and my testing is better now than it was yesterday at this time.

If you are concerned this offset in temperature probes did NOT affect earlier waterblock tests that were posted; it was an issue with waterblock outlet temperature measurement and that wasn't used in those reviews.

//edit: Another good lesson; looks like my 8K3A socket lugs are a bit dogeared and that the MCW5000-A is a good bit better than the above results would indicate when extra care is taken in mounting.

BillA
02-07-2004, 12:29 PM
Bill a question about your heatpipe:

If you go low enough in power applied do you see a flat C/W vs power region? I'd expect that you'd hit a point where there isn't enough heat to cause a phase change in the pipe. Then if you keep boosting power over the heatpipe's working range far enough does it return back to that same flat line? Where you just add so much more heat into the system that the heatpipe doesn't work because the cold side is too hot?

I am visualizing a situation where at really low and really high power (temperatures completely outside the heatpipe's operating range) that you get performance that is pretty similar to just the heatsink alone, and that only within mfgr specs is there a big improvement by adding a heat pipe.

I have never personally used a heat pipe though so I could be way off base about how they supplement convective cooling...
I too would guess that at extremes, a heat pipe is a lump of copper,
and a 'good' plot would show the hysteresis curves;
but really at extremes

excess local heating will cause the 'vaporising area' to dry out, and that is the end of the heat pipe until it is cooled and re-condenses

not too sure I would agree with "supplement convective cooling", while convection is one of the mechanisms utilized, a 'heat pipe solution' would utilize the heat pipe as the primary transport mechanism

pHaestus
02-07-2004, 01:12 PM
But if only transport is involved then shouldn't C/W remain fixed? It has to serve as another repository for CPU heat to lower the C/W, correct? Or does the C/W have a different meaning now as you have basically "lowered the thermal resistance of copper"?

Brians256
02-07-2004, 02:21 PM
But if only transport is involved then shouldn't C/W remain fixed? It has to serve as another repository for CPU heat to lower the C/W, correct? Or does the C/W have a different meaning now as you have basically "lowered the thermal resistance of copper"?

I'll jump in. Please correct me if my understanding is wrong.

C/W does not remain fixed because the transport mechanism in a heat pipe only works for a defined range of input power. This is why (in my opinion) heat pipes stink for general purpose usage. They have to be made for a specific heat load, which is fine for a manufactured system, where you match the heat pipe to a known CPU with known heat output. For consumers, you'd have to select a heat pipe for your particular CPU and then swap it out if you overclocked it differently.

Heat pipes work by depending upon a pool of liquid that evaporates from the hot end, travels to condense on the cool end, and then uses capillary action to migrate back to the hot end (repeat ad nauseum). This mechanical action of moving the phase change liquid (I doubt it is water, it is probably an alcohol or cheap refrigerant) depends upon several things.

If the hot end isn't hot enough to vaporise the liquid, then no heat pipe action occurs (no phase change).

If the hot end becomes too hot, then it "dries out", as Bill mentioned. The cool end may be able to recondense the liquid, but the liquid may re-vaporise before it reaches the hot-side.

BillA
02-07-2004, 02:39 PM
But if only transport is involved then shouldn't C/W remain fixed? It has to serve as another repository for CPU heat to lower the C/W, correct? Or does the C/W have a different meaning now as you have basically "lowered the thermal resistance of copper"?
the thermal resistance of a specific heat pipe varies with the heat flux density of the source (not the case with wbs and hsfs)

I do not yet know as a demonstrated fact, but I strongly suspect that there are several additional parameters which also influence the heat pipe's efficacy (thermal resistance), and I will be isolating and testing these in the future
- the capillary plus vapor 'transport'
- the condensation at the 'cold' end

not a DIY device in anything other than the crudest sense
Brians256 is correct

Groth
02-07-2004, 02:50 PM
As long as you're looking for more tests to do, I'd be interested in see how the vapor pressure (and thus coolant boiling point) varies with heat-load. :)

BillA
02-07-2004, 02:54 PM
As long as you're looking for more tests to do, I'd be interested in see how the vapor pressure (and thus coolant boiling point) varies with heat-load. :)
ah Groth, gotta love it
you gonna design, build, and gift the probe to me ?

Groth
02-07-2004, 03:32 PM
Can't afford a pressure transducer? Hmm, I guess one question that should have been asked is, are you making prototypes in-house, having them made, or are you just playing with someone else's pipe?

BillA
02-07-2004, 03:44 PM
eh ?
the pressure transducer is not the difficulty,
it is its insertion into the heat pipe after the fact

looking only for the moment

Groth
02-07-2004, 03:59 PM
Ah, yes, it is a bit limiting if you're only looking at complete pipes. :shrug: No playing with coolant or charge or wicking or dimensions. meh.

Incoherent
02-07-2004, 04:10 PM
...wasting lots of Les's and incoherent's time...

Don't feel bad on my account, I absolutely do not consider this a waste of my time, especially considering the amount of time (and effort, and money ...) you are spending obtaining this data for us to pick away at.
I am just happy that the errors are stable enough for them to be detected, a testament to your consistancy.

Heatpipes, and their requirement for a specific heat load. I wonder if these Shuttle SFF CPU coolers take that into account. There appear to be four seperate pipes. Could they all be tuned to different optimum heat loads? in effect creating a "wide band" heatpipe cooler...
It is a shame they are so specific. It's a pretty neat mechanism. I am very curious as to what you are working on Bill.

Cheers

Incoherent

BillA
02-07-2004, 04:24 PM
every day is a new lesson, just chuggin' along

Les
02-07-2004, 05:34 PM
The variation in power from last night/this am's data? At very low flow rates it's difficult to perfectly insulate the hoses and I suspect that the 0.5GPM flow number is somewhat suspect for that reason. For the numbers above 2GPM the delta T is so small that better resolution than 0.01C is required (a difference of 0.01C corresponds to nearly 10W). The numbers from 0.75-2GPM are pretty much dead even at 72-74W; not much variation of CPU power with flow in that case.

If you mean the earlier test results then there was a 0.06-0.07C offset in my temperature probes that I didn't catch (but incoherent did).

As for Bill's graph, consider that we are dealing with water inside a heat pipe, and that water has some interesting properties which occur near phase transitions. Solid water floats, for instance.

Yes the sensitivity and the accuracy of the probes is sorely tested by this work.
Notwithstanding,Incoherent's admirable method is a tool to determine the solution. The "0.07c systematic error" suggestion is a the value to give a best fit to an invariable W . The invariable W is questionable.
Using an offset of 0.07c is prejudging that W does not vary with Flow-rate. I don't think this can be done.

I may not be understanding correctly but pHaestus has suggested two evidential values for the systematic error - 0.06/0.07c and 0.02c.
I probably prefer the 0.02c solution which shows an increase of "Heat Absorbed" with increasing flow rate. However, if had to bet, I would choose a value between 0.06/0.07c and 0.02c as giving the true variation of W with flow-rate( this best corresponding with my preconceived notions of the variation of "Heat Absorbed(W)" with "C/W").
Some graphs:
http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh3.jpg

http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh4.jpg http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh5.jpg http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh6.jpg

Think will catch up on the Heat Pipe discussion much later. However I imagine that wb's behave similar at a high enough temp when Flow Boiling can be envisaged.

pHaestus
02-07-2004, 05:48 PM
Les: 0.02C is the offset in my current setup after moving thermistors around and swapping one out. It is only valid for last night's (Swiftech MCW5000-A) data. In that test run the W varied from 69-75W but I am a bit skeptical of the numbers above 2GPM.

As for the earlier results I don't think much can be done to be conclusive other than repeat tests again. Shouldn't be a big issue though as many more blocks have to be tested and data collection is free.

Groth
02-07-2004, 05:58 PM
Heatpipes, and their requirement for a specific heat load. I wonder if these Shuttle SFF CPU coolers take that into account. There appear to be four seperate pipes. Could they all be tuned to different optimum heat loads? in effect creating a "wide band" heatpipe cooler...I wondered about that, too. Plus, a heatpipe will have optimal temperature range. How wide? How does that range relate to coolant and charge? How much will the thermal impedance vs. heatload curves change over the temperature range? Could using two coolants with different boiling points give a wide-band cooler in a single pipe?

Brians256
02-07-2004, 06:19 PM
I wondered about that, too. Plus, a heatpipe will have optimal temperature range. How wide? How does that range relate to coolant and charge? How much will the thermal impedance vs. heatload curves change over the temperature range? Could using two coolants with different boiling points give a wide-band cooler in a single pipe?

I think you have hit the nail on the head, as those have been the questions in the back of my mind for quite some. time. However, I have not seen any information about this in public literature. So, if the answers exist, they are either in proprietary care or they are in expensive books that are not in my library or on the internet.

I do think that using a multiple coolant heatpipe would greatly widen the effective sweet spot. I also think that even a single coolant heatpipe would probably have a wider sweet spot than we fear. For example, Bill's heatpipe data shows that it works fairly well for a ten to twenty watt range in heat input.

BillA
02-07-2004, 06:22 PM
Les
just poking at the semantics here

"The invariable W is questionable." WRT pHaestus' testing, that W (net to wb) is variable is certain, only the rate of change is in question.

"Using an offset of 0.07c is prejudging that W does not vary with Flow-rate. I don't think this can be done." In a strictly absolute sense you are probably correct, at least with anything my setup can document. More loosely speaking however, I can and have repeatedly demonstrated that within 'reasonable' limits the device C/W is independent of the applied load (but NOT for heat pipes).

Once I have a testing 'peer' (get with it pHaestus !), I will be better able to identify the slight 'apparent' influence that changes in the applied power may induce. One needs multiple benches to verify that an 'effect' is not an artifact just of that particular bench.

pHaestus
I observe a very slight increase in the coolant temp rise (at the lowest flow rates where such is most visible, 0.01 to 0.02°C) between wbs with a high C/W as compared to others with a lower C/W. In these cases the bp is at a higher temp, which implies a different energy 'load'. Be interested to see if you see the same.

Groth
and you haven't even touched on wicking structures and fabrication methods, lol

Les
02-07-2004, 07:09 PM
Les
just poking at the semantics here
.....
More loosely speaking however, I can and have repeatedly demonstrated that within 'reasonable' limits the device C/W is independent of the applied load (but NOT for heat pipes).
.......



Not my intention to suggest a device's "C/W" is changing with heat load. A device,here, is considered to be a particular wb with a particular coolant flow.Each point on the "Watts Absorbed" v "C/W" graphs are separate devices with different "C/W"s.

BillA
02-07-2004, 07:15 PM
ah, ok
was looking at the 'set' of points, rather than individually

pHaestus
02-07-2004, 07:31 PM
A practical observation:

When I remount the MCW5000-A (using one hand to hold clips onto lugs and other to work the screwdriver) the mobo's power circuitry is both very close and very hot. It's hard to imagine that at least a little of this heat doesn't make its way into the waterblock via the baseplate and top. And the amount would be pretty wb dependent (the Swiftechs are a lot closer to these parts whereas the long 4 hole wbs are instead closer to the northbridge).

BillA
02-07-2004, 07:57 PM
and . . . . .
is this too not part of the reason for bench testing ?

are we testing the system (of which the mobo is a part), or the wb (independent of the effects of the other parts)?

perhaps I've not been paying attention, but why are you not using your heat die ?

pHaestus
02-07-2004, 10:42 PM
heat die still involves sinking substantial dollars into it (need 2 good DMMs, PSU, insulation, etc etc). Time and money, time and money.

Plus I am a bit of a masochist; can't you tell from my hobbies?

Groth
02-08-2004, 01:15 PM
pHaestus, have you seen those cones veterinarians put on dogs? How 'bout using a similar approach - blow some significant air on your voltage-regulators and northbridge to minimize the extraneous heat, but protect the CPU/block from spurious, non-reproducible air currents.

Bill,
Wicking? All the possibilities of material, fiber shape/size, weave (or not), bonding, thickness, and how all of those interact with all the other variables. It makes water look easy and friendly. When can we expect your data? ;)

joemac
02-08-2004, 05:17 PM
PH would it be possible to drill into the blocks you have to obtain a temperature reading. This would allow you to easily insulate a small hole rather then trying to control a larger environment. I don’t know how feasible this would be on some blocks but I think it would provide a real insight to what the temperatures look like between the heat source and the transfer medium.

TerraMex
02-08-2004, 05:34 PM
Doesnt WW, Cascade and RBX blocks have a very very thin base ?
If it could be done:
Wouldnt that influence the blocks performance...?

joemac
02-08-2004, 06:30 PM
Doesnt WW, Cascade and RBX blocks have a very very thin base ?
If it could be done:
Wouldnt that influence the blocks performance...?

I don’t think the base is thin through out the entire block. I think the only thin part of the RBX and the WW is over the core in which case the probe hole can be made to be stop just outside the valley of the block. This should prevent affecting the performance reading of the block (most user only care about the reading above the core). Frankly without the proper insulation on the test, this should remove more variables than it introduces.

prandtl
02-08-2004, 06:48 PM
I don’t think the base is thin through out the entire block. I think the only thin part of the RBX and the WW is over the core in which case the probe hole can be made to be stop just outside the valley of the block. This should prevent affecting the performance reading of the block (most user only care about the reading above the core). Frankly without the proper insulation on the test, this should remove more variables than it introduces.
IF something like this was to be done, it would mean the temperature probe will not be at the same position (in respect to the core) for all wbs, wich will make any datas useless for any wb to wb comparison.

pHaestus
02-08-2004, 09:28 PM
joemac:

Not sure how to back calculate "W" from a baseplate temperature? The insulation is definitely a problem for the 3 barb blocks, but honestly I am not so interested in this now that I found out that weird results were operator error :)

I will, if there is interest, run tests as function of MHz and Vcore using whatever block is on my testbed this week (it's the aquajoe atm). There's a catch though. Can get someone (Les? Incoherent? Groth?) to use results to come up with better radiate-style equations for CPU power using my data? :D

Les
02-09-2004, 03:20 AM
1) ... but honestly I am not so interested in this now that I found out that weird results were operator error :)
..........
1) Can get someone (Les? Incoherent? Groth?) to use results to come up with better radiate-style equations for CPU power using my data? :D

1) Suggest that for the MCW5000A the relatively small increase of Wwb with increasing Flow rate is,perhaps, a consequence of only a small change of "C/W" with flow rate.
http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh7.jpg http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh8.jpg

or as I insist on plotting ( I share Bill's unease but ....)
http://www.jr001b4751.pwp.blueyonder.co.uk/pHugh9.jpg

Think it is a little early to judge the issue.

2) I only do beer-mat sums not computer equations.

bigben2k
02-09-2004, 01:40 PM
Nice. How about power vs flow, for the last 4 blocks tested? I'd just like to see the variation in the power. I see what you mean pHaestus. Would you foresee any benefit in having 3 decimal resolution, I mean, do you think that it would be practical?


From my limited understanding of heatpipes, they are designed to work at a specific temperature, i.e. the boiling point of the liquid inside the pipe. So as a cooling solution, you have to take into account the gradient, between the liquid and the CPU, and it is going to depend on the power being supplied, as well as all the usual variables (TIM joint, notably). Bill's graph is representative indeed: the heatpipe relies heavily on the latent heat (energy from the change of phase) of the liquid being "boiled", so if the temperature is outside of that range, the performance relies strictly on the conduction/convection of the remaining metal assembly, which will be poorer. Many more variables... Testing these involves a different approach than for WBs (as Bill demonstrated). I've had the chance to think about that particular one, ever since I was asked to test one a few months back (had to turn it down: not ready to test yet!). It's a real nightmare, but one I suspect may become part of future cooling products, under one form or another.

Incoherent
02-11-2004, 02:39 AM
joemac:

I will, if there is interest, run tests as function of MHz and Vcore using whatever block is on my testbed this week (it's the aquajoe atm). There's a catch though. Can get someone (Les? Incoherent? Groth?) to use results to come up with better radiate-style equations for CPU power using my data? :D

pHaestus, if you come up with the data, I would certainly be happy to give it a shot. I am not a programmer though so it would only be a set of functions which fits your data, in Excel sheet format, not a radiate style program.
Of course this is assuming that we are able to identify and account for all the dominant parameters, at best it would be a "typical" value in a typical system, presented as "CPU power output minus secondary losses" Data at a range of water temperatures would be interesting. I would expect to see a Power/Temperature curve upon which the true CPU power output would lie somewhere.

Les, your C/W vs W chart is very disturbing, I do not like it. I can not imagine a situation where power output is dependent on anything but CPU temperature, applied voltage, speed and load level so I do not want to see anything but noise in such a chart where the above parameters are constant. Flowrate is irrelevant. Anything else, any trend, linear or curve in such data says that there's either a measurement error or in fact one or more parameters are changing. Although of course, in reality all these parameters will change within a certain range, maybe predictably.

Thinking.

Cheers

Incoherent

Les
02-11-2004, 04:33 AM
....
Les, your C/W vs W chart is very disturbing, I do not like it. I can not imagine a situation where power output is dependent on anything but CPU temperature, applied voltage, speed and load level so I do not want to see anything but noise in such a chart where the above parameters are constant. Flowrate is irrelevant. Anything else, any trend, linear or curve in such data says that there's either a measurement error or in fact one or more parameters are changing. Although of course, in reality all these parameters will change within a certain range, maybe predictably.

Thinking.

Cheers

Incoherent

Some wordage:
1) The inputs are sources' heat and paths' resistances.
Varying the flow rate changes the resistance of the "die>contact area >water" path. Changing a path's resistance will effect the source's temperature.Would expect increase in heat through the "die>contact area >water" path as its resistance is lowered.
"C/W" is the "die>contact area >water" resistance.
"Heat absorbed" refers to the heat absorbed by the water.
2) IF heat only reaches the water by the "die >contact area>water" path then the plotted "C/W" is the "C/W" and "Heat absorbed" is the Heat passing through the "die>contact area >water" path.

Plotting measured "C/W" v measured "Heat absorbed" explores both 1) and 2)

Incoherent
02-11-2004, 08:02 AM
Some more incoherent ramblings
Some wordage:
1) The inputs are sources' heat and paths' resistances.
Varying the flow rate changes the resistance of the "die>contact area >water" path. Changing a path's resistance will effect the source's temperature.Would expect increase in heat through the "die>contact area >water" path as its resistance is lowered.
If the die temperature decreases (which it does). Then the loss via secondary paths is reduced. More heat is flowing via die>contact area>water path. Agreed.

"C/W" is the "die>contact area >water" resistance.
Also in Fouriers equation Q=k.A.dT/L, dT/Q or C/W, is equal to L/kA. I prefer to think of it in those terms, changing flowrate changes the effective L or A or k or all of them. These are physical parameters, if they are changing then your statement about the points in the chart being like individual waterblocks is a good one. I guess C/W is convenient.


"Heat absorbed" refers to the heat absorbed by the water.
2) IF heat only reaches the water by the "die >contact area>water" path then the plotted "C/W" is the "C/W" and "Heat absorbed" is the Heat passing through the "die>contact area >water" path.
Plotting measured "C/W" v measured explores both 1) and 2)
If we adjusted the water temp to maintain a constant die temperature at the different flowrates, the secondary path gradient would remain unaltered, even though the primary "die >contact area>water" path C/W's changed with flowrate. The "Heat absorbed" is constant. If you plot this again at several temperatures I am not sure there would be any relationship except the "Heat absorbed" changing with temperature. Point being, I think the C/W vs W chart is only a few points in a chart that is filled with data points, ie every C/W can have any W so there is no trend to be gleaned.

I'll keep thinking, I am a little muddled here.

Cheers

Incoherent

BillA
02-11-2004, 09:21 AM
"If we adjusted the water temp to maintain a constant die temperature at the different flowrates, the secondary path gradient would remain unaltered, even though the primary "die >contact area>water" path C/W's changed with flowrate. The "Heat absorbed" is constant. If you plot this again at several temperatures I am not sure there would be any relationship except the "Heat absorbed" changing with temperature."

interesting
I can do this both on an insulated heat die, and a ttv (~mobo + CPU)
will report - eventually

Les
02-11-2004, 09:46 AM
"If we adjusted the water temp to maintain a constant die temperature at the different flowrates, the secondary path gradient would remain unaltered, even though the primary "die >contact area>water" path C/W's changed with flowrate. The "Heat absorbed" is constant. If you plot this again at several temperatures I am not sure there would be any relationship except the "Heat absorbed" changing with temperature."

interesting
I can do this both on an insulated heat die, and a ttv (~mobo + CPU)
will report - eventually

Data from heat die tests in any insulated condition may be revealing.
Having a leisurely re-look at your ancient data http://www.ocforums.com/showthread.php?s=&threadid=65078&perpage=30&pagenumber=2
Look forward to the eventuality.

BillA
02-11-2004, 09:57 AM
jeez Les, a thread from 2 years ago ?
yea, needs a re-look

Les
02-12-2004, 06:21 AM
Have re-looked and possibly only seen the sensitivity to measurement.
This was very early Billa work since which equipment has been upgraded innumerable times.
Have included data in graph from Incoherent's thread (http://forums.procooling.com/vbb/showthread.php?t=8433&page=5&pp=25)
http://www.jr001b4751.pwp.blueyonder.co.uk/SecW5.jpg

The cascade data plotted here are the preliminary data reported here (http://forums.procooling.com/vbb/showthread.php?t=8433&page=4&pp=25)