Gmat has showen us some links and math that I dont get, but it is very good stuf for ppl that understands it.

I though......who does know the answer to all this questions etc. Well it surely must be the carmanufactors....because if they create an very efficiant heatcore, they will only have to make it "small" and thereby they will have less expensives. And that is there interest. So these guys must "know it all" when it comes to heat transfering. Well then it sould also be the best heatcore's around because....the know what they are doing. Therefor......buy a auto heatcore made of cobber and with the right measures to fit your case and you would be pleased. Or is every thing I said wrong ?

NoSoup: consider my silence as a total agreement.

Quickmcj: You got it right. Actually the very 'heater cores' you can buy from D-Tek and various watercooling shops are auto parts or slightly modded auto parts.
Look at threads started by hmale, there's one where he shows his new heater core. It's designed to cool down race car engines up to 600hp. It will be used to cool down a PC, he he he.

Besides, bb2k started this thread to talk about *pressure* issues in rads. Do we want low or high pressure ?
From my (modest) knowledge:
- we want pressure to work for us, not against us.
- there *are* pressure differentials throughout our water lines, and not negligible, even with our tiny pumps.
- the very few serious tests i've seen tend to prove that low pressure in rads (as opposed as high pressure in WB) is a good thing.
- i've yet to talk to a fluid dynamics expert (i know a few, ill see them this WE) about this, because this problem is clearly over my current knowledge (heck i'm a computer scientist, FD courses are a few years back...)
- this problem does *not* involve flow or temperature. We're talking about pressure here.

I have seen the tread from Hmale......didnt bother to write it in here :)

As I mentioned before..., this really is unrelated to this thread (which is about flow but should be about pressure). But I'll reply quick to this here.

1. You will have a hard time mounting pelts onto a rad without restricting air-flow through the rad (assuming you want the pelts on one of the water channels)

2. You still need to cool the hot side of the pelts.

If I'm bored later today I'll start a new thread and explain my entire theory and the possible solutions I've come up with so far.

Gmat, what are those serious tests? I don't see how pressure (and *not* flow) can be important. Suppose you attach an extra pump to the bleed line, and this pump is trying to pump air in or out changing the pressure inside your system. Do you think this can have an effect on cooling? Why?

Actually i'll talk to an expert tomorrow and we'll discuss about that precisely.
For what i understood so far, there's a relation with Bernouilli equations, Euler equations, and flow acceleration through local low pressure zones.

Sirpent I dont think going so far is going to be of help, though i'll try to consider this as well. All i wanted to consider was our common WC problem, aka pump->rad->block or pump->block->rad (neglecting a res).

More on that tomorrow.

(edit) btw serious tests were a rad round-up on overclockers.com (ask BillA for this, if my memories are correct).

First of all, my apologies. Much of what follows is sure to upset some folks that have posted in this thread. I intend no disrespect and have no desire to upset anyone, but I find it hard to read the mix of fact and fiction found here. For the most part, people stating claims have been correct. Unfortunately, there are interspersed errors and misinterpretations mixed in with the rest.

gmat,

You've got a pretty good grip on most of this, but some of your statements make me wonder. You have obviously studied the topic of heat transfer, and most of what you've said is true. Some of it, though, is nonsense. To your credit, you're only referencing someone else's flawed results.

Someone posted about this on AMDMB a couple of weeks ago. My reply: "Absolute garbage".

Heat transfer from a surface to a liquid or gas depends on many factors including surface shape/roughness, delta-T, and myriad fluid properties (most of which are temperature dependent). For incompressible liquids, pressure has no bearing on heat transfer. Sure, if you wanna get technical, water is compressible, but its bulk modulus is ~200,000 psi. The pressures in our systems pale in comparison.

It's also an error to state that pressure always changes from positive to negative. This too depends on a couple of things. First, if your system has an open air reservoir, then the only regions of below-atmospheric pressure reside in the pump casing. Second, if your system is truly sealed, the suction line may be at less than atmospheric pressure. Usually it will be, but if your system was filled with relatively cool water and heated, the expansion of the water will create a static pressure higher than atmospheric. Whether or not you get a vacuum at the suction then depends on elasticity of the tubing and the overall temperature rise of the fluid as well as flow rate and velocity in the lines.

Anyway, getting back to the overclockers thing, I'm specifically referring to a claim that relocating the block and radiator lowered this guy's temperatures on the order of 3°C. This is absolute crap. A system dumping 100 watts into the fluid (75 W CPU and 25 W pump) needs only about 32 gph to keep the peak water differential to 1°C. Claiming a 3°C change only tells me that the guy doesn't know what he's doing.

Sorry if I sound like I am going off on you, but just want folks to fully understand that pressure has no bearing on heat transfer coefficient of an incompressible fluid (aside from determing flow rates).

NoSoupForYou,

You said something about delta-Ts and radiators that didn't sit right. Perhaps I've misinterpreted your meaning.

Not really. You are forgetting the other side of the equation, er, radiator. The heat transfer from the fluid to the tubing in the radiator is generally not the limiting factor in radiator performance. What is usually limiting is the air flow across the radiator. A higher fluid flow rate will reduce the (already really, really low) temperature differential between fluid and tubing walls. This is normally smaller than the delta-T between air and tubing, especially at the fluid inlet to the radiator.

This next bit also applies to the argument of "parallel" radiators or flow rate through radiators. It should be completely obvious that a radiator will deliver its "best" fluid outlet temperature if the fluid stays in for a very, very long time. Given enough time, the fluid will eventually reach the ambient air temperature, for all practical purposes. On the opposite extreme, very high fluid velocity may leave insufficient time for the heat to escape. This should also be obvious. Imagine a radiator with a fluid flow path one inch long. No way you could get the water to cool off because you'd have insufficient time and area to get the job done.

Everyone isn't using huge radiators simply because:

1) There's only so much room.
2) You can get all the performance you need with a reasonable sized radiator. Beyond a certain point, you have rapidly diminishing returns.

To all,

There is a disconnect for some understanding the relationship of pressure, flow rate, flow velocity, and heat transfer. Pressure along with flow resistance determine flow rate. Flow rate divided by cross sectional area determine flow velocity. Flow velocity, and not pressure or flow rate, has the largest impact on heat transfer coefficient.

What a good block does is transform upstream pressure into high velocity. It does this by reducing flow area. The pressure drop that occurs over the block is much like the spray nozzle we put on our garden hoses. It you run a hose with no nozzle, the water comes out with good flow rate, but not impressive speed. A spray nozzle drops the overall flow rate (like a water block), but results in much higher velocity in the flow that remains. This is the key to getting good heat transfer in the block, where all energy must pass through a very small area.

Velocity is also the key in the radiator, but it's the air velocity that is key. Increasing air velocity allows decreasing radiator size and dwell time.

Again, sorry if any feelings got hurt and sorry for such a long post, but hopefully it helps clarify some things.

Wow, dude. You just dropped science!!! How is it that you know all of this stuff?

LOL, I'm going out on a limb and guessing that yours is not a sarcastic reply. If it is, so be it. If it isn't, I'll answer truthfully. UW-Madison BSME and many years in industry working on hydraulic and heat transfer systems. Biggest heat transfer unit I ever worked on was ~3500 kW consisting of a couple of fuel oil burners heating oil to ~550°F for a paper mill. Biggest chilled water system probably on the order of 30 tons (archaic engineering units, most home CA systems are ~1-1/2 tons). IIRC, 12000 BTUs = 1 ton, so I guess about 360,000 BTU chiller.

Lately I've taken to writing miscellaneous heat transfer guides for AMDMB trying to share the knowledge, translate the engineering geek-speak, and dispel myths. Haven't really got the time I'd like to devote to it, but having fun anyway.

myv65, I've enjoyed your post very much and it is very well thought out. I think perhaps your oversimplified description leaves some doubt.

Quote, "It should be completely obvious that a radiator will deliver its "best" fluid outlet temperature if the fluid stays in for a very, very long time. Given enough time, the fluid will eventually reach the ambient air temperature, for all practical purposes. On the opposite extreme, very high fluid velocity may leave insufficient time for the heat to escape. This should also be obvious. Imagine a radiator with a fluid flow path one inch long. No way you could get the water to cool off because you'd have insufficient time and area to get the job done" end quote

If the heat delivered to the rad is in very small quantities then the time needed to dissipate is also small in the rad. The amount of heat absorbed per volume of water before it reaches the rad is smaller in high flow but repeated many times over compared to low flow in the same time frame. Is my understanding in this flawed?

Thanx ! That was exactly the kind of answer i wanted to read. :cool:
Actually my system is:
* closed loop, no res, no airtrap
* sealed
and tubes / pipes are rigid.
Given :
* the quite high flow restriction of a waterblock and our small tubes,
* the way our centrifugal pumps work (they are not volumetric, they only work by applying a pressure), the pressure differential in a working pump between inlet and outlet should always be around it's head pressure,
* the quite low temperature differential accors the circuit (1°C or less). Is 1°C enough to produce a noticeable static pressure ?
i've been wondering what was the *real* pressure distribution around a closed loop of water. Maybe CFD would answer that..
You seem to say that in every case the pressure is positive around the whole circuit, which i doubt by experience. (say, i only "doubt", ie i may be quite wrong on this).
What i'm considering here is the dynamic effects.
In a turning flow; the radial kinetic forces tend to create a pressure on the outer side, and an underpressure in the underside (Bernouilli, if my memories serve me right). This effect is mostly noticeable in rads ans waterblocks, under CFD or other flow analysis tool scrutiny. The question is, whats the difference when "ambient" or "static" pressure of the flow at this point is "high" or "low" ?

Notes:
* I doubt that with rigid tubing the pressure "suddenly" drops at pump inlet. Correct me here if i'm wrong.
* i've got a rather powerful pump (rated at 27W), but i doubt it dumps all its 27W in water. Actually it's quite hot to the touch, and since it has fins i suspect it dumps a good part of its heat in the air. Besides the engine (hot part) is totally insulated from the water chamber, since it's a mag drive. The percentage of heat dumped by the pump into water has been a hot topic but until now i've seen no convincing answer.

gone_fishing: you got it right.

I'll tell ya, I'm not sure if I should reply here or to another thread running around here that says basically the same thing. You are correct in all aspects, but you don't really state a conclusion. Barring that, I can't say if you are right or wrong.

I posted that last bit late at night and didn't really put down quite all I wanted. Well that and the fact it was already a really long post. :rolleyes:

Just about everyone seems to get the fact that energy input to a cooling system is almost constant regardless of flow. It is not quite constant because processors don't put out truly constant heat and pump energy will change ever so slightly as system temperature (and fluid viscosity) change. So if we ignore these minor changes, we can say that flow rate multiplied by delta-T equals energy transferred. Not stating anything new here.

Somewhere else in another thread, JimS said something like what you said above. Namely, the percentage of time water spends in the radiator is independent of flow rate. His reasoning thus went along the lines of at flow = 1X, the water is in the radiator 5% of the time. At flow=2X, the water is still in the radiator 5% of the time. Cooling should therefore be roughly equivalent.

The fact is, energy transferred must be equivalent, which means that the delta-T at 1X is two times higher than the delta-T at 2X. This says absolutely nothing, however, about the actual fluid temperatures.

Also, consider a person that uses a reservoir. Given the same tubing and flows, maybe their fluid only stays in the radiator for 2% of the time. Assuming the same flows, does this mean that their radiator somehow performs poorly in comparison? Absolutely not. A radiator has no "brain" to know that is has the water for 5% versus 2% of the time. It knows only flowrate (fluid AND air) and temperatures.

There is no steadfast answer that applies to all situations regarding "what's the best flow". The general rule-of-thumb answer is "use as much flow as possible without dropping the residence time in the radiator too much". OK, so that doesn't really tell us anything. What does it mean?

It means that heat transfer in an air-cooled radiator by its very nature has its peak cooling at the entrance and its minimum cooling at the exit (as fluid and air temperature approach one another). When the residence time is too low or the air flow is too low or the surface area is too low, the delta-T between fluid and air must increase to get the same quantity of heat transferred. When residence time is high and air flow is high and surface area is high, the fluid will exit at practically the same temperature as the air. As you begin to decrease any of the three variables, the fluid-air delta-T will begin to increase. It will increase gradually at first and more dramatically as you continue dropping residence time/air flow/surface area.

So long as you don't "go over the hump" where the delta-T curve gets very steep, the flow through the radiator is not yet too high. Simple to state, hard to put an absolute number on it (and it's a different number for every setup).

I don't have my texts with me, they're at work. Water reaches its peak density at 4°C. It is sort of parabolic going away from 4°C. 1°C won't change the density much, probably on the order of 0.01-0.1%. To know the pressure rise, I'd have to verify this number, know the tubing rigidity, and look up the *real* bulk modulus. You may be surprised how much static pressure such a small temperature change can generate if the system is truly rigid.

No, I don't say that pressure is positive around the whole loop. It may or may not be, depending on the system. I will guarantee you that it is positive in an open system provided the reservoir is at the high point. In an open system, it may be under a slight vacuum in the last leg if the reservoir is at a lower elevation.

In a closed system, "most" often it is at a slight vacuum leading to the pump suction. You can easily change this with a standpipe filled with water, though you may need a higher ceiling. ;) If you place a T ahead of the pump suction and run a vertical (open at the top) line and fill it with water, the water height in that run will define the pressure at the suction (and eliminate any chance of having a vacuum). This is obviously not a practical way to run a system, but does serve to illustrate some points about pump systems.

I'm not quite sure what you're getting at with your comments about radial flows. Yes, there are secondary flows caused by bends and temperature changes among other things. Yes, they create localized variations in velocity. This manifests itself as localized variations in convection coefficient. Sure, you could model this with CFD, but your answers are only as good as your assumptions placed on the model.

More practically, you can run pressure taps at the inlet and outlet of each individual component if you want to know the overall restriction imposed by each part. Knowing the delicacies of secondary flows may be useful to a block designer, but I've seen little evidence that the major manufacturers really understand what they're doing from an engineering standpoint. Fact is they don't have to understand it well. I say this for two reasons. First, marketing drives sales because the majority of buyers buy stuff that "looks cool" or they heard about from a buddy. Second, there really isn't a dramatic difference in performance among the main blocks. So long as the block is sufficiently restrictive as to create a high velocity via a pressure drop, it'll do just fine. Where blocks will disappoint is if something else in the system constricts flow so much that the block velocity is too low.

To answer your final question about ambient or static pressure, it's irrelevent. Static pressure by its very definition is the same in all directions. This means that it can't affect flow rate (other than increasing flow area in soft tubing), so has no, repeat no effect on heat transfer. Relative pressures determine flow rate and are all that really matters.


Item 1, you are correct. Sudden drops only occur when there are sudden changes in the flow path. Fittings, bends, Ts, valve bodies, etc., cause "step" changes in pressure. Tubing causes a linear "loss per length" based upon flow and internal surface roughness along with Reynold's number.
Item 2, tough to answer. Most motors run on the order of 80% efficiency. Most centrifugal pumps that we use peak out around 60% efficiency. This peak occurs when discharge resistance is moderate, neither a minimum (peak flow) or a maximum (dead headed with zero flow). Because of our systems, we tend to run higher head pressure on the pump than the "peak efficiency" head pressure. So figure your pump is ~40% efficient overall. It also doesn't run at 100% rated motor current, say maybe 80%.

Take all this together and you probably dump ~27*.8 (load)*.2 (motor inefficiency) as heat from the motor fins. The remainder of energy input (27 * .8 * .8) gets put into the water. Of this, flow rate * delta-P (outlet - suction pressure) is "useful work" and the remainder is pure heat. Even the useful work is still energy, though, so is energy that enters the system and must be removed by the radiator.

Tell ya what, I'm part way through a series for AMDMB discussing all facets of water cooling. There's also a couple of articles discussing heat transfer and fans. For the water cooling parts, all that is currently posted is the introduction and pump section. The fluids section should be up within a week or so. The real fun starts with the next one after that covering radiators and blocks. There's sure to be material there that throws some people into a tizzy fit. If you haven't already seen it, feel free to stop on by for a look. The pump article is "stickied" in the liquid cooling forum and the others are "stickied" in the cases&cooling forum.

myv65, is it true that as long as we think in terms of delta-Ts for the radiator and waterblock (ignoring frictions in the system), changing the flow rate does not make any difference in the cooling efficiency?

Sirpent,

Your question represents a potential can of worms. Strictly speaking, efficiency is generally defined as useful work produced divided by required energy input. In cooling, I would interpret this as minimum cooling system power consumption while keeping the computer operational. Under this strict definition, lower flow will always win because chips can run a lot hotter (at stock speeds) than we tend to let them. Again, strictly speaking you can cool a top end XP at stock speed with room temperature water flowing at a rate of about 1-2 gph provided you've got a block designed to work with that flow and can stomach the temperatures you'll have.

If you've got some other definition for "cooling efficiency", describe it and I'll give my best shot at an honest answer.

myv65,

By efficiency i ment the (lower) cpu temperature under given heat produced by cpu and given ambient temperature. But my question was rather about idealized equations (proportionality of heat transfer to delta-T's) than about real life situations.

It wasn't sarcastic. Glad you didn't take it that way. I guess you'll have to pardon my mannerisms.

Very educational. :D

Yup, the can's open! Lowest CPU temperature for a given ambient will vary from system to system and chip to chip. At one extreme, you could have flow so low that convection in the block was awful. In order to carry "X" watts, the water would need to go through a large delta-T and due to the low flow/convection coefficient, the chip would need to be a lot hotter than even the warmed fluid. At the other extreme, you could conceivably pump far more energy into the water just to pump the volume than what energy the chip would add. Delta-T in the fluid would be extremely low, but at some point you may have rising temperatures simply because of the energy needed to pump the water around.

Call it cheating on my part, but there is no single answer that covers every system. There is, however, a general rule that most systems will provide a lower cpu temperature as flow rates increases.

More practically speaking, performance from one system to another will depend far more on how you set things up than anything else. Put your radiator in a spot where it has trouble getting air, bad news. Get a block that refuses to clamp down properly, also bad news. Do everything right and you'll be hard pressed to find more than a few degrees C between decent systesm.

My only real beef with designers of this stuff is that they don't do things as efficiently as possible. Given water's specific heat, you don't need much flow to get the job done. What you *do* need is high convection, aka high velocity in the block. With the right porting, you could cool the CPU with <20 gph easily. Why this matters is that it would allow smaller pumps and smaller radiators. I'll admit that the delta-T in the fluid would be higher than a system running ~75 gph, but so what? The cost, both purchased and operating, would be lower. I guess that's why some things ya gotta do yourself. It's also why I won't be running a pre-built system any time soon.

Thanx myv65, you replied all my questions.
To resume :
1 - static or ambient pressure plays no role in heat transfer. That means the order of pump, rad, block would be determined by local deltaT rather than local pressures.
2 - Higher flow produces better cooling.
3 - consider that we take care properly of other problems (air flow through rad, elements position, etc..)

Besides i'm considering building a custom radiator. Every small bit of valuable engineering info is welcome.

Moreover i've yet to see an efficient "low-flow" system. Yes money can be a consideration but i dont see any other interest. Given a fixed system, increasing the flow will always increase heat transfer (up to the point where the pumps dumps too much heat - in our situation it's not the case).


Sirpent: "myv65, is it true that as long as we think in terms of delta-Ts for the radiator and waterblock (ignoring frictions in the system), changing the flow rate does not make any difference in the cooling efficiency?"

i'm not sure of what you mean, but if you mean "heat tranfer" the Fourier formula Q=UAdeltaT answers it. Q=heat tranfer, A = contact area, U = heat coeffficient, which depends on such things as turbulence and flow. U will get higher if flow gets higher...

As I see it higher flow is better but for the people selling this stuff to the masses they don't want the word to get out. And I say why not! The simple fact that people are willing to buy watercooling when it is really not needed for a computer to function proves that they are willing to pay for the absolute best.
Opinions?

Thanks, myv65!
I think I agree with most of what you wrote. But, still, my question was slightly different. Probably I just didn't use the right words. I'll try to be more precise. I'm building a simple mathematical model of the situation (trying to keep worms in their can).

So assume that we have an ideal situation, where the cpu generates a given wattage, all the heat goes to water, the air temperature in the case always stays the same, and we can vary the water flow in the system without generating extra heat. Suppose that the heat flux F1 from cpu to water equals C1(Tcpu - Twater-wb), where Twater-wb is the "averaged" temperature of water in the waterblock, and the heat flux F2 from water to air equals C2(Tair - Twater-rad), where Twater-rad is the "averaged" temperature of water in the radiator and Tair is the "averaged" temperature of air (the arithmetic mean of the in-case and exaust air temperatures). For simplicity, we can even assume that Tair is the (supposedly constant) in-case temerature. In a stabilized system, we have F1 = F2 = (heat generated by cpu); and we can also think that Twater-wb = Twater-rad. Two biggest difference between this simple model and the real life situation are, imho, the following: (1) in reality, C1 and C2 are not constants, they depend on the flow (or, really, local velocity, as you wrote, but the flow is our only input parameter) - higher flows mean higher numbers; (2) higher flows generate more heat even if the pump is 100% effective (and it's not). The two correction terms work one against another and it seems that the first one usually wins in the typical range of applications (higher flow -> lower cpu temperature). But my question is: is it true that in the simplified model (I think it's really the simplest possible one) the cpu temperature does not depend on the flow?

I don't know how big or how small are changes of U in a typical system (any data?). So I am asking what are the answers for the "first approximation" model where U=constant.

very lucid comments myv65

having several hundred pages of obsessively detailed measurements, I would add several observations

while the design basis of wbs could be different, the necessary pumps to obtain the higher convection rates are hugely more expensive
I'm looking at an Iwaki mag drive gear pump that has nominal 'ratings' of 36 gph @ 45 psi; list over $650;
and another 'big boy' that delivers 92 gph @ 75 psi lists for $1050
(max flow, max pressure; not both together, eh ?)
continuous duty positive displacement pumps are not cheap, and never will be

the smaller rad is quite 'doable' in terms of dumping the heat (with LOTS of air/noise),
the problem lies with the resultant system equilibrium temp of the coolant
- with the present wbs, a higher coolant (inlet) temp at the wb will always result in a higher CPU temp

looking forward to your article

be cool

Dunno whether this approaches the description but:

I have made a simple 50 x40 x 0.8mm chambered Copper waterblock ,with 6mm thick base which should give a velocity of ~ 1.7 m/s at a flow rate of 50gph.(hope my sums are correct)[Edited sums on Oct 30th(changed from the wrong ft/s to correct m/s).

http://www.jr001b4751.pwp.blueyonder.../P0001076a.jpg

Unfortunately this easy to construct "flat" geometry has a high flow resistance.
Flow rate ( radiator in separate cooling circuit) 25-30 gph with 600 lph (unknown max head) pump,and 45-50 gph with Eheim1250(1200 lph, max head 2.8psi ).
Cooling a Morgan1100 and stressing CPU with Jouni Vuorio's Stabilitity Test got( 3 seatings):

http://www.jr001b4751.pwp.blueyonder.co.uk/Flowa.jpg

Intend to disassemble wb and fit with central water inlet to look-see at the infleunce of "Die Area Impingement".

Well this is OT but i'll answer by another question. I want a total silent (aka fanless) cooling solution for my ultra-high performance PC (max OC'ed AMD, ultra160 drives and so on). I want it to be portable and "not too big". My answer is watercooling. Got another solution ?

Sirpent,

You're really asking a question on radiator performance since a block will alway yield a higher convection coefficient with higher flow. Rather than get into gory details here, I'll try to make certain I give this topic its proper due in my next article at AMDMB. Actually, I've got a short one on fluids due to go up very soon, but that's already finished on my end. The next one I'm working on is radiators and blocks and will hopefully address a lot of the questions posed here and elsewhere.

Les,

1.7 ft/s is actually a very low flow velocity. Is this the "average" velocity in your block? Most of the pumps we use will crap out with peak velocity in our system around 10 fps or less. If we keep velocity in our tubing and radiator relatively low, with a spike entering the block we'll generally be close to "optimum" performance for a given setup.

gmat,

A few months back a guy wrote me from Europe seeking input on a pump-less water cooling system. His intent was to cool water to ~4°C and allow natural flow to develop based on the fluid losing density via heating in the block. I was skeptical, but upon running the numbers figured he could cool his chip with ~1 gph and a 20°C delta-T in his block. If that's enough density variation to generate 1 gph, he may be onto something. It is definitely not an over-clocker's solution, but can't be beat for quiet operation. I did not inquire about his source for getting 4°C water, but would hazard a guess that he'd use a TEC with large passive heat sink on the hot side.

Unregistered (BillA :p),

I owe you an apology. Based purely on second-hand comments, I took a couple of shots at some of your work. Not sayin' the comments won't be warranted, LOL, but I should say nothing without being certain of the true content. I have no excuse other than a natural ability to stick my foot in my mouth occasionally. I've read some of your stuff and found it to be of much higher caliber than most of what's available out here. Indeed, I'd like to discuss your radiator article in relation to my own prior to completing my work.

In the future, I'll try to get all the facts straight from the source and discuss one-on-one rather than going off half-cocked.

No comments from me yet (busy for next 4 days) but a quick noted I posted/found here:
http://forums.procooling.com/vbb/sho...4238#post34238

Like i stated, i want maximum overclocking.
Yet i wont go through the hassle of installing a chiller or a TEC. For one thats way too expensive (money doesnt matter, up to a point). For two it has too many drawbacks (reliability, moisture, weight, power supply problems...) to be a convenient solution.
If you want "low performance" but totally silent cooling the solution is heat pipes (passive phase change cooling).
But in my case i'm cooling just every hot part (CPU, GPU, NB, HDs, maybe RAM...) so encumbrance is a constraint. And i want to be able to carry my box :)

(edit) for those who don"t know them heat pipes use passive phase change convection to "pump" heat out of a tiny surface, to bring it to a big rad. This, without any moving mechanical part.

Yes. Calculated "average" velocity..
I am afraid calculating the velocity profile is beyond me.
Was hoping for 3x the average velocity( ie 5m/s for Eheim1250)[Edited Oct 30th (getting units mixed)]
Higher velocities were hoped for because with the Eheim1250 could get 150gph(US gal) in a Maze2.2 with a guessed X-sec of 36sq mm vessus the the 32sq..mm. Sums were very iffy in the first place not to mention failing to take account of the higher drag of the "flat" geometry.
Maybe the maximum velocities ,over the die area, approaches these values.
Thanks for taking the time and trouble sharing your knowledge expertise.

Les

wrt the die area:
open up the flow area to, and from (in the top plate)
then 'pinch' the flow from the sides (you're not trying to cool the corners)

and look for a low volume/high pressure pump
then you can put a good 'squeeze' on it

be cool

Bill.
Yes/No to both profile and pump.

It depends on which direction I take.
Have 3,enthusiasm dependant, plans:
1) Look-see at DAI by fitting a central inlet (keeping 2 oulets and same internal dimensions)
2) Obtain some Diode temps to compare with my "In Socket" Peltier temperatures - initial reason for getting a Diode reader.
3) Look-see at the inclusion of an intermediate shim and a crack at that TIM analysis nightmare - have you any intentions of a revisit?