Using Cathar's block, assuming that 0.19 C/W is improved by 10%, that would equate to a 1.3 deg C improvement, assuming also the same conditions for the 0.19 measurement (70 W source).

I think that 10% is awfully optimistic: I'll have to see it to believe it.

[edit: miscalculated, see below]

My basis for this is the data posted by since87 in the first post whereby Hard copper had an electrical conductivity 89.5% of that of soft copper.

For the majority of materials which use elecron motion in thermal conduction, there is a linear relationship between electricla conductivity and thermal conductivity.

I'm not 100% sure about this but I will be revising "electronic structure of materials" over the next few days, and there is mention of the relationship between thermal conductivity and elctrical conductivity.

Actually, I suppose, I could just dig it out later on today. Will post my findings later.

8-ball

Also be aware, that it depends largely on the initial level of cold working and the level to which the recrystallisation goes to completion.

8-ball

the relationship between thermal and electrical conductivity is well understood
(no need to cite the refs)

Null-A Ben
yet again, think harder
it is ONLY the thermal conductivity that is being changed,
not ALL those factors that together form the basis of a wb's "C/W"
jeez, you gotta start checking what you say before you post it
where we at now ? 4500 posts ?
goddam Null-A

Ah yes, minus the 0.05 for the TIM, leaving 0.14 for the block... 0.98 degrees.

What else did I miss?

Differences in temperature gradient across the "furniture" of the block and changes in heat spreading.

I think what BillA is trying to get at here is that thermal conductivity of the material is not simply a constant which is, say, multiplied by a factor based upon the design of the internals to provide an efficiency.

Changing the thermal conductivity WILL change the temperature difference between the water and the cpu, but, for the same reason that this happens, the way the heat gets from the block to the water will also change.

(Note that I am not educated in the area of heat flow, so my choice of words may be incorrect at times, but so long as the general idea gets across, I'm happy)

As you know, the heat flux is the thermal conductivity of the material multipied by the temperature gradient. So, if we have increased the thermal conductivity, and the net heat flux is to remain the same, the thermal gradient must have become shallower.

Lets take White Water as an example and lets suppose it is now made of Aluminium

The thermal conductivity is lower, so the temperature gradient must be higher for the same heat flux. This means that there will be a higher the baseplate will be at a higher temperature than the fins (steeper gradient) as compared with the situation in the same block made of copper, where the temp gradient will be shallower.

This will affect the way the block transfers thermal energy.

I guess what I'm trying to say is that the relationship between thermal conductivity of the block and it's C/W is not a linear one.

Also note, this is grossly over simplified, there are other factors to take into account. This was merely an explanation of a point to be made.

8-ball

Null-A Ben
the above post is an example of why 8-Ball's posts will be read for their content
and in contrast shows how yours confuse, mislead, and obscure every single aspect you purport to comment upon
200 vs. 4400

sad, eh ?

Didn't realise I'd broken 200:D

It was about thirty a few weeks ago, and then I decided that I should start revising for my finals.

Strange isn't it, that the start of my "revising" and the start of my mad posting marathon coincided like that.

Could have something to do with me being 2 weeks behind on my revision schedule.

8-ball

[EDIT: I suppose I did have to do "some" revision to be able to post everything in this thread;) ]

Actually, I'd rather think that it poses questions, hence the question marks, but to each his own.

ok 8-ball
thats it,
you're banned 'till after finals

Regards

@bigben,

Ben, you often seem like a programmer that's trying to create a massive program but has only a list of programming terms to use and none of the understanding of what those terms actually do. You're able to type in the terms, but don't seem to understand the syntax. Bill's point here is that the "C/W" of a block is more than simple conductivity. In the loosest sense, C/W implies a temperature change based on heat load. In the specific case of Bill's testing and waterblocks, it means the temperature between the base of the block and the water flowing through it.

This means that a block's C/W is really two-fold (ignoring minor stuff like convection to air off its surface and virtually zero radiation energy exchange). The first part is conduction of the heat through the block structure. The second part is the convective resistance getting that heat into the water. This second part is purely a surface phenomenon and other than how the heat is distributed over the surface, conductivity has nothing to do with it.

This is why dropping a block's conductivity by 10% via cold-working is not so bad. Conduction through the block is probably (just an off-the-cuff guess here) about 50% (ideal would be 50%) of the C/W of a block. So improving conductivity by 10% would mean a delta-T reduction of about 5% of the delta-T that occurs from block base to fluid.

A change of this magnitude is piss in the wind when compared to the variation that Bill gets from one block mounting to the next. The only way this is measurable is a test geared specifically toward a measurement of conductivity, which not even Bill's fancy get-up could manage.

I'm all for folks exploring the unknown and seeing what's possible, but I prefer to be realistic about the potential benefit. The potential of this one is not so big, especially when compared against using "good" copper versus a lower conductivity alloy or aluminum.

I'm probably just confused, but it was my impression (I looked over a few of his tests, but I'm kind of stupid) that BillA's C/W numbers meant the difference between the die and the water flowing through the block, and that would include the thermal interface material layer. Am I wrong? Thanks.

Your question is best answered by Bill, but I'll say that he has made an attempt at quantifying the resistance of the TIM joint so that the actual differences in block performance may be better approximated. The main point I was illustrating above is that the block's conductivity is only a portion of its total thermal resistance. The overall block performance is dictated by both its internal resistance (conductivity, material, and "internal" geometry) and its convective resistance (surface geometry). A good block design balances these two.

theetruscan
several different terms used

"C/W" in quotes is the die to coolant inlet temp difference ÷ Watts
it is in quotes as it includes the TIM joint offset which is not actually part of the wb, and also because the "C/W" is related to the flow rate

T/W has been used to denote the thermal resistance of the wb itself and was experimentally obtained with a TC or RTD in a hole in the bp 0.52" off the bp face
- this had some problems with the hole placement verification
but this data was used to try to quantify the TIM joint thermal resistance (a 'correct' C/W as it is a constant, for a given mounting)

C/W will appear again shortly in a writeup on ThermalDesign rads,
and in another article on rad and fan selection
- this C/W will use the difference between the air and the mean coolant temp (heat exchangers normally use the log mean temp difference but with the small deltaTs it is not worth the effort)

it is NOT correct to say that the TIM joint has a C/W of 0.05
my data suggests a value of perhaps twice that (the 0.05 value was in a 'what if' discussion)
(perhaps Les recalls the threads on OCAU where this was thrashed out - to no definitive conclusion)
Aavid has some good papers describing the calorimeter setup to make such measurements, mine is not really suitable

Maybe so, but it's still an interesting topic, and folks are clearly interested in it. And to be honest, looking at the experimental data I dug up, it's not exactly that hard to do, 15 minutes in the oven at 140 C.

So the difference may not be huge, but it will make a slight difference, and with the level we've managed to get blocks down to now, it's gonna be that much harder to improve the C/W.

Plus it's intellectually stimulating tossing these ideas around. Isn't that what people do around here, toss ideas round.

8-ball

Yes, but I suspect we are talking of maybe 1% increase in Thermal Conductivity due to the decrease in dislocation density.
Like yourself I have no data.


J.M.(aka Les) Round (BSc, Phd, - Metallurgy, Leeds(1963 -69) - Mentor P.M.Kelly)

Indeed Dave.

I was hoping to remind the main participants that if there's a resulting application, it ought to be outlined in such a way so that one can understand the purpose of it: I think we lost Hara a couple days back.

I understand the concept of the crystaline structures within the copper, and I can somewhat follow how a certain process may yield an improvement, but I do indeed need to understand better the extent of the potential improvement, as it applies to a waterblock. Sometimes I'll state something that I know is incorrect, to sollicit an answer (to BillA's great frustration ;) )

For those interested in this topic, but not able to get too deep in it, I'd recomend an old pocket book that I found most interesting:
"The new science of strong materials", by J. E. Gordon (mostly about structure, not about conductivity).

Kelly as in Kelly and Groves

That book got me through my first year exams

That said, it still depends largely on the degree of cold working which provides the driving force for recrystallisation.

Remember, we do have data for the difference in electrical conductivity for cold drawn copper and soft copper, a difference of just over 10%.

Greater stored energy due to cold working will provide a greater drving force for recrystallisation, increasing the nucleation rate, resulting in a finer microstructure, which would probably not have as high a conductivity as a similar sample recrystallised from a lower state of cold working.

8-ball

No. Pat not Tony.

Even though there is a direct relation between electrical and thermal conductivity.

8-ball

8-Ball
I think your quote is a misrepresentation.

"Neither of which are particularly relevant to thermal conductivity and low temp strees relieving."
(Pasted - including spelling mistake)

elaborate?

"Neither of which are particularly relevant to thermal conductivity and low temp strees relieving.":-
Two values(10% and 2%) for differences in Electrical Conductivity between an "undefined annealed condition" and a hard drawn conditions. I, perhaps mistakenly, take the annealed condition to be a Soft Anneal* which is several hundred degrees above the recrystallization temperature.
I am not sure how one can relate this conflicting data in ,possibly, the Soft Annealed Condition to stress relieving at the suggested temperaures of 100C or 140C.

* As defined here http://www.key-to-metals.com/ViewArticle.asp?ID=25

"the annealed condition to be a Soft Anneal* which is several hundred degrees above the recrystallization temperature"

while I was but a simple lecturer at a Uni, this too is my understanding of it

I see your point.

8-ball

@Bigben2k

Could you log on to yahoo messenger or contact me regarding a radial waterblock design

Thnx ;)

pm = private message.

probably more appropriate.

Here is a data sheet ( http://216.239.57.104/search?q=cache...C10200.asp</a> ) for the alloy of my block ("C10200 has conductivity 101% IACS, the highest among coppers."). This suggests 700-1400F for annealing. Since my block has skived fins, the conductivity gains should be good. Also, since I am working with a 300+ Watt heat flux (TEC), even a .01 C/W improvement will result in a CPU several degrees cooler.

My proposed process:
1. Lap on .000150" flat calibrated granite (400, 600, 1000 grit)
2. Anneal to 1400F in argon
3. Quench in water (my research indicates method of quenching makes no difference with Cu, water is fastest)
4. Lap on granite (1000, 1500, 2000 grit)

Any suggestions?