New block (Hysterical post)

[Incoherent]

DO NOT TRUST ANY OF THESE MEASURED PERFORMANCE NUMBERS, my thermometry is now suspect

I have just started testing a new block I have come up with.
Comparing the results to those I have for my Crater block from My die sim and pHaestus' measurements, I think it is close to a Cascade/ MCW6000. Could even be significantly better with work.
There has been a lot of thought gone into this one. It is a departure from the thin baseplate idea, having not less than 11mm of copper between die and water.
Some comments from Jabo (who seems to have moved away from this forum) were an impetus, regarding a spherical type of block.
This IS a hemispherical block. I'm seeing as low as 0.169C/W at 3.76lpm on my setup. This compares to .19 for the Crater block with the same pumps, before TIM settling.
Some logic to the design.
A thin parallel baseplate block has a fairly linear thermal gradient through the copper, a high "h" is possible because all the water can be concentrated on a small area. A Cascade.
A thick parallel baseplate has a less linear thermal gradient, the thermal resistance of the copper gets progressively lower the further from the die you are but it is offset by an increase in average delta L ; the "h" is normally (but not necessarily) lower due to the water being spread out over a larger area, area increase being approximately proportional to L^2, but the larger area itself is an advantage. MCW6000.
A hemispherical baseplate has a very nonlinear thermal gradient, the coppers thermal resistance decreases rather rapidly as delta L increases. L stays as in a parallel heat channel as cross sectional area increases proportional to 2pi*L^2. This is the key; relative to the available surface area, the distance between water and die is low. The problem is to maintain a high convection coefficient.
This is done in this case, as Jabo suggested, by reducing the height of the block structure clearance. I've done this progressively radiating out from the inlet. At the outer edge of the block the clearance between block and middle cap is 0.5mm.
This maintains the water velocity down the slope of the sphere and thereby a reasonable convection coefficient. The structure I have not optimised at all, the object was to test the concept.
Some pictures, sorry about the quality:







As a bonus you get to see my bodgy die sim.
I will post some better pictures of the internals later.

Incoherent

[nikhsub1]

Very very interesting I must say. Look forward to more results!

[SlaterSpeed]

I wanna see what kind of inlet jet your using?

[Incoherent]

Originally Posted by SlaterSpeed

I wanna see what kind of inlet jet your using?

None at all. The "inlet jet" is the hose barb. As I implied, this is an unoptimised proof of concept. An improved surface structure, accelerator nozzle(s), better mounting method and so on will be on Maxah Mk II.
I will post a picture tomorrow of the middle plate, it is kind of cool in a simple sort of way.

[BillA]

hmm
I may have missed something ?
how are you addressing the convection from the sides of the riser ?

[killernoodle]

Looks very nice, kind of like a 3d radius. I could see a CNC lathe pumping these things out very quickly too. Interesting concept, I like it.

[bigben2k]

The idea is right, not so sure about the implementation! (follow Bill).

It looks nice though!

Looking forward to more pics, and details of sim.

[Incoherent]

Originally Posted by unregistered

hmm
I may have missed something ?
how are you addressing the convection from the sides of the riser ?

Refering to the Fluxblock under the block Bill? Some neoprene goes there, it was removed at the time the picture was taken. I can't seat the fluxblock properly when it's insulated.
The test setup is unfinished (actually barely even started), I must stress that, but it is in the same state as when I measured the Crater, and it seems repeatable to within about 0.005C/W.
W from fluxblock, lpm from bucket and stopwatch, T average from many samples of thermistors and heater has a R spec of 200ppm/C (fluxblock takes care of that I hope, I see a clear variation in W output with Temp, haven't verified with V and I measurements yet, don't trust DMM thanks to you Bill). So distrust my numbers at this point. The die sim is bodgy.

(Hysteria is waning...)

[jaydee]

Interesting!

[pHaestus]

BTW incoherent

Your "swiss cheese" wb completely soaked my test system when its top sprung a leak and has removed the will to test from me*

*Some of the above is exaggerated, but not the "watery grave for pH's test system" part

[HAL-9000]

This design looks like a far more advanced and refined approach of the Alphacool Cape, the link for which:

http://www.alphacool.de/perl/shop.pl...1&art_id=12118

The Alpha too seems to have the successive "steps" forming a pseudo-hemisphere (or in the Alpha's case, a Christmas tree). But no CNC'ed top, and way too tall. Nowhere near as nice as this one.

[Etacovda]

Originally Posted by pHaestus

BTW incoherent

Your "swiss cheese" wb completely soaked my test system when its top sprung a leak and has removed the will to test from me*

*Some of the above is exaggerated, but not the "watery grave for pH's test system" part

Ouch.

I had a similar idea for a block, but theres no way i could do it that well! Nice work

[Mars]

Nice looking block. It also looks effective. Your relults should confirm your theory with a proper test bed. PH's hands are kinda full these days. I've seen a site, with a homemade test bed that was quite accurate. I think it was on overclockers.com.

[Incoherent]

Originally Posted by pHaestus

BTW incoherent

Your "swiss cheese" wb completely soaked my test system when its top sprung a leak and has removed the will to test from me*

*Some of the above is exaggerated, but not the "watery grave for pH's test system" part

Oh Shite. I am so very sorry, what's the damage to your kit?
I was pretty sure that cap was sound, damn damn. Another polycarbonate victim?
I feel very bad about this.

[Incoherent]

Some of the rational.
Note that with these numbers the spherical BP can perform similarly to a parallel BP with half the convection coefficient.
The numbers are all imaginary but somewhat based on sense.

Edit: Fixed a mistake in the charts, miscalculated parallel area and L

[Les]

Overall I agree with your rationale
However have difficulty with thumbnail 1(now graph 1,again)
Dealing only with parallel bp
For given bp area, say 50x50mm, h(eff)=50kw/m^2*c(=h(conv) no surface structure) and varying thickness.
Would split the resistance into components :



Used Waterloo for calcs
Did not include zero thickness (logic probs)

Dunno how to calculate for hemispherical bp.
Intuitively think will be improvement

Thumbnail 2(graph2) is similar to my original flat bp guesses(presented here,for example)

Dunno how much using hemisphere would alter the situation

[Les]

Ah, you have swopped thumbnail 1 for 2
Plus modified the new 2.
Will digest

[Incoherent]

All the numbers that I have generated are from "thin slice" or "thin onion ring" kind of average summing. I have found many ways of calculating the resistance of a parallel BP but the hemisphere eludes me too. Some talks with the mathematics PhD's at work are yielding a few ideas but nothing I am happy with at the moment. Partial differential equations are really not my thing I have decided.
It's a deceptively tough problem to model.
Am interested in your beermat sums Les.

[Les]

Main prob with beermat sums is the beer usually takes precedence over the sums.
Have added the 100kw/m^2*c case to graph

[Incoherent]

Originally Posted by Les

Main prob with beermat sums is the beer usually takes precedence over the sums.
Have added the 100kw/m^2*c case to graph

Looks familiar.

Some internals:









A better image of the Base.

A remount and cleanup gave a small improvement to the numbers.
It is averaging 0.166 C/W, about 0.023 C/W better than the Crater.
I think this might exceed the Cascade. Hard to say though because the Crater was so restrictive, for a given pumping pressure it may be worse.
Need Pressure drop.

Les, a thought about the C/W vs BP thickness. I'm basing my numbers on a changing water/copper interface area using a 45 degree assumption. Waterloo is maintaining a constant interface area is it not?

[Stang_Man]

interesting.... looking forward to furthur testing and revisions..

[Les]

Originally Posted by Incoherent

....
Les, a thought about the C/W vs BP thickness. I'm basing my numbers on a changing water/copper interface area using a 45 degree assumption. Waterloo is maintaining a constant interface area is it not?

Yes, Waterloo uses "user defined" interface dimensions(in above case 50x50mm).
This corresponds to the "Flux Channel Dimensions"
It then calculates:
"One-D Resistance (C/W)" = Resistance of 50x50x*mm slab of Cu + Convective Resistance of 50x50mm surface/interface
"Spreading Resistance (C/W)" = The extra conductive resistance due to heat-source being smaller than flux channel.
"Total Resistance(C/W)"= "One-D Resistance (C/W)" + "Spreading Resistance (C/W)"

The "Spreading Resistance (C/W)" is Dependant on both h ( "Film Coeff", h(conv)no surface structure) and dimensions(both source and channel).
Not happy with the 45degree assumption.
Waterloo in effect calculates the correct angle for the thermal conditions.

I use Isoflux Rectangles program, however they do Non-Isoflux cases for disks.
I calculate to 6 digits and use 1000 "Terms"( have no justification for choice)

Note X-axis in my 2nd graph is wrongly labeled; should be "h(bp to fin) W/m*m*c)" - was early days and was very much struggling with designations(still am)

[Incoherent]

Have Waterloo updated their site recently?
They have a "Spreading Resistance of Circular Source on Circular Disk with Edge Cooling" which I have never seen before. It appears to generate almost zero spreading resistance with any kind of convection on the edges. This is the closest I have seen to simulating a hemisphere. I think that for the hemisphere spreading resistance might actually be close to zero, it's a radial thermal gradient of constant L.
This page is also useful.
My biggest problem is to figure out what is going on in the area just above the die at radii less than the die size, I am at the moment assuming a hemispherical surface of the same area as the die as a start point for the onion layers. Squashing this flat would give a similar geometry to the actual block but I know it's not quite right.
Share your unhappiness about the 45 degree thing, there are more accurate ways. Simple though for illustrating the idea and maintaining continuity of calculation method (slices and shells).
Edit: I think I'm leaning towards your way (skipping 45deg) . I'll recalculate.

[Les]

Do not think Waterloo have updated for years
"Spreading Resistance of Circular Source on Circular Disk with Edge Cooling" is not new.
Have difficulty "getting my head round" all the edge cooling answers.so have not used to any extent.
Same applies to the non-isoflux conditions

I assume you have followed Groth's thread , maybe some clues there as to "what is going on in the area just above the die at radii less than the die size"

[Les]

The "45 degree thing" may prove to be ok, but I think it is begging the question.