Testing waterblocks vs pumping power

[Cathar]

Been thinking on this problem a bit and attempting to find a way to convey to an everyday user what waterblock performance is like.

The problem with flow vs C/W graphs is that they do not convey any pressure based information. One can look at a graph of two blocks of two vastly different levels of restriction, and performance per LPM may be higher than the less restrictive block, but the less restrictice block will perform better per unit of pressure drop.

Then we get to the issue of a pressure drop vs C/W graph, where real world pumps do not provide a constant pressure drop as flow rate varies. So while in the example above the second block performs better per unit of pressure drop, it will also be allowing a higher flow rate due to its lower restriction, and so any centrifugal pump that is applied to it will apply less pressure to that block, than to the first more restrictive block.

Ideally we have to present both graphs for a full picture, and the reader needs to analyse and understand both graphs.

That's how it should be done, but it's requires substantial work to glean an overall picture from 4 graphs (flow vs C/W, pressure vs C/W, block pressure vs flow, pump PQ curve). In order to present a composite picture of block performance vs pumping power, then how about the possibility of displaying a graph that is just that? Basically a graph of waterblock C/W vs Pumping Wattage?

So I was thinking about how to present such in an easier to understand picture, and thought that DC pumps presented one possible answer. Using a variable voltage power supply, and tracking the current that flows through to the pump, one can measure how much pumping power is being applied to the cooling loop. On top of the other charts, plot a C/W vs Pump Wattage chart.

There are some drawbacks to this approach though, and primarily it falls down to the test loop's resistance. Pumping power gets spent overcoming all the restrictions in the test loop, and we would not test loop resistance to be terribly high. The way around this though would be to calibrate it. Plot a graph of the test loop's pump power vs flow rate curve with no waterblock in the test loop. Then when plotting data points for a tested waterblock with a certain amount of pumping power, adjust the pumping power by subtracting the test loop's required power at whatever flow rate is being measured. In this manner I believe that the pumping power vs performance curve can be easily calibrated to remove the test loop's characteristics from being an influence.

The second drawback, which is perhaps more serious, is what to exactly use as a pumping model. There are high-head/low-flow pumps (Laing DCC), and high-flow/low-head pumps (Eheim 1250), and there are pumps that fit somewhat in the middle and offer both (Laing D4). We would probably be after a middling sort of DC pump that offers up to ~20LPM of peak flow for the ultra low flow resistance blocks, and up to 10mH2O of pressure head for the ultra high head favored blocks.

That could be achieve in one of two ways. Either by putting 2 x Laing D4's in series, or by using a pump like an Iwaki RD-30 which at 24v offers 10mH2O head and 20LPM flow. Both types of pumps do support running at very low electrical powers (through decreased voltage). The D4's in particular can run as low as 1W each before failing to turn any longer, and can handle being run at up to 15v easily (for 5mH2O pressure head, or 10mH2O for two pumps in series), or at about 25W of pumping power each.

Thoughts? Would this be an appropriate way to present an easier to understand mosaic of waterblock performance that encompasses a good approximation of real world pumping characteristics with varying pumping power in a single easy to present graphing format that the layman can look at and determine which blocks are good for which pumping power scenarios, and for any given pumping power, which encompasses both flow and pressure, what to expect?

[Corrected some statements that were missing adverbs]

[bigben2k]

I've always believed that it should be acomplished in the easiest way:
1-run the performance test, using either flow or pressure

2-run a pressure versus flow test. (no performance measurement there)

The two data sets can be used to interpret the results in one way or another.



I think your real question is more about how a reader can use the info. The WB performance graph that pH is using now is pretty nice; if there was a way to do the same thing by overlaying pump curve, that's be interesting, but it wouldn't account for the rad, nor any of the fittings/tubing. Fitting/tubing info is easy to obtain, but the rad is still a big black spot in the WC community but then, the same graph becomes really, really complicated.

[pHaestus]

In MY opinion, the solution is to produce C/W vs flow data and dP vs flow data for waterblocks and a few common radiator/fan combos. Then to use that data along with the other components in the loop and the pump P-Q curves to predict a final C/W for the system. That is what groth was going for here:

http://pages.sbcglobal.net/water.groth/Dorky%20process1.htm

The interface would have to be simplified a lot and it's awaiting my dP vs flow data...

It's waiting on my dP vs flow numbers to be generated; that's next up after this Alphacool nexxos XP review is done

[Chew_Toy]

The one curve that I would like to see for blocks is flow through the block vs pressure. The way I see to get that info would be to set the block up in a loop with a powerful pump like the md30rz with a valve on the outlet folowed by a flow meter and then a accurate pressure gauge. That way tou could plot the flow vs pressure of each block just by varrying the valve and take the flow and pressure reradings. I have always been curious on what the flow in my system is and have thought about putting in a 0~5psi guage on the outlet on mine. That way as long as the pq curve of my pump is accurate I could get the flow by plotting the pressure reading to my pq curve.

[pHaestus]

I have a Rosemount dP xmitter and a 5.5 digit DMM. I just haven't had the time to make it happen. This weekend I hope it will be time. I don't have enough space downstairs to set up that test loop without dismantling part of the existing one. I think we're at a break between wb releases though so this is a good time.

[Cathar]

In MY opinion, the solution is to produce C/W vs flow data and dP vs flow data for waterblocks and a few common radiator/fan combos. Then to use that data along with the other components in the loop and the pump P-Q curves to predict a final C/W for the system.

That IS the correct way to do things, but it involves work on behalf of the reader, and work that many are unwilling to even learn to understand what they need to do to interpret the results properly.

The issue that I am attempting to confront here is that of reader laziness. As in a approach of "Okay, so all this technical stuff just flew over your head? That's cool. If there's one graph which you should read, try to understand, and take away with you as an approximated summary of the results seen, it would be this graph".

[redleader]

Why not just provide C/W per dP graphs? Given that, are C/W verses flow graphs even relevent? Its not like most people have any way to gauge flow, while their pump max head is published, and you can make educated guesses about what a radiator does to that figure.

[Cathar]

Why not just provide C/W per dP graphs?

...because pumping pressure is not constant as flow rate varies...

[lolito_fr]

For direct comparison between blocks, I think that using C/W vs Power is a good idea. I'm not so sure about the methodology of using a real pumps' input power though.
Why not use Hydraulic Power, or more simply Flow*Pressure? (based on P/Q data AND C/W vs flow)

[Les]

For direct comparison between blocks, I think that using C/W vs Power is a good idea. I'm not so sure about the methodology of using a real pumps' input power though.
Why not use Hydraulic Power, or more simply Flow*Pressure? (based on P/Q data AND C/W vs flow)

As suggested and explored by Since87 here (http://www.ocforums.com/showthread.php?t=250729&page=2) in post 26.

[lolito_fr]

Not quite(?) Unless I misread it...
(I find Since87's graphs rather confusing)
Will try and codge something up in Excel to illustrate (see if it works?!)

Edit:

http://img103.exs.cx/img103/5748/nexxosxp.gif

I only have Cathars graphs to work off for the PQ data, so unforetunately the inclusion of the 1/2" tubing + rad is going to mess things up somewhat. (I would have liked to plot 2 or 3 blocs on this graph to compare)

[Les]

My understanding was he was suggesting plotting C/W v dP*Q .

[Cathar]

As suggested and explored by Since87 here (http://www.ocforums.com/showthread.php?t=250729&page=2) in post 26.

Indeed, I remember that now too. Definitely a better approach by using hydraulic power, rather than pump input power. A "unified" approach to cooling performance assessment?

Thanks for the link Les. Will go over it, hopefully with a clear head.

Edit: Just saw lolito_fr's graph above. Yes - that's pretty much exactly the sort of thing I was hoping for.

[lolito_fr]

Bingo.

http://img105.exs.cx/img105/4841/nexxos-mcw6000.gif

no less than 6 pages of excel!!! (more work than I bargained for)
usual disclaimer - GIGO (+fair chance of rounding errors, etc)
Not to mention the involuntary inclusion of pipe losses and rad losses, however I think this is a pretty good illustration of Cathars idea:)

[Les]

lolito_fr
Yes, I like your graph (http://img24.exs.cx/img24/3441/nexxosmcw6000.gif) and yes not quite the same as suggested by Since87.
Will also investigate(slowly) further when head clears

[Cathar]

Thanks lolito_fr.

One possible improvement to the graph to clarity sake may be to make the power axis logarithmic. 1W of hydraulic power goes a long way and there's an awful lot of information contained in the 0.01 to 1W range, and somewhat less in the 1W to 10W range. Would seem to me that a logarithmic power scale might space out the plots a little better for comparison layout purposes.

[lolito_fr]

Sorry Les, that graph is way out - have just edited my post.
As suspected, too much haste + head not sufficiently cleared.

Cathar, yes, will try a log scale when I get this little prob sorted out :)

[Les]

lolito
Good.
Was just about to embark on a data check - saved me the trouble.
Will still do, but will postpone till after todays pub


(temporarily deleted graph - have just found a major mis-calculation :mad: )

It is a problem when posting calculations made "on the hoof"
I am constantly having to correct my own mis-calculations.

[Cathar]

I was able to re-use data that I had input from my simulator thing and wrote a custom perl script to munge it into a usable data set. I removed the rad + tubing effects. This is the graph that I arrived at. Re: the logarithmic thing - given Phaestus's data it would appear that since the flow rates don't go down low enough that 0.3W is where the graph starts from anyway. Where this will get gnarly though is for blocks like the DangerDen Maze4 which have a very low pressure drop, and 0.3W of hydraulic power equates to around 8.5LPM flow rates.

http://www.employees.org/~slf/curves/pumps/power/stormg4pwr.png

[Edit: Oops - corrected the axis labels - reload page to see correct labels]

[lolito_fr]

Cheers Cathar. I now need to remove the rad+tube effects!!
No Perl scripts here unforetunately:(

Here is a log version of the above corrected graph

http://img105.exs.cx/img105/7176/nexxos-mcw6000-log.gif

enjoy!

the Nexxos seems to be holding up surprisingly well (even against the G4) ...
but of course the rad will play a part :p

[Cathar]

Oh, now THAT is interesting isn't it?!

[lolito_fr]

Well if you are referring to the straight lines, my dT vs Power graphs are both best matched by power functions:
y = 10.08115*(x^-0.03524) for the MCW
y = 9.52474288*(x^-0.08522324) for the Nexxos

Other than that, then yes the Nexxos seems to whip butt :D

[Cathar]

Here's what I managed to work out, with log axis:

Edit: Graph deleted due to computational error

[Cathar]

Quite frankly I find the near straight lines most fascinating.

Edit: I was plotting the G4 line from the Procooling test results graph page, and noticed that it is different from the separate line graph that Phaestus posted. I will need to confirm with him tomorrow as to what's up there.

[Les]

Cathar
You seem to be having a good day with your arithmetic(or perl thingy -whatever that is).

Edit Removed wrong comment.

[Cathar]

Perl = interpreted scripting programming language with syntax derived from C, java, awk, sed, and sh. Not great for large-scale programming because it requires discipline from the coder to not create unreadable code. Great for small scale munging of data sets. Incredibly powerful language but with more than enough syntax ugliness to hang oneself very quickly.

[pHaestus]

flow Storm G4
0.26 13.80666974
0.5 11.26556618
0.75 10.17413799
1.02 9.334698438
1.22 8.977748337
1.5 8.533861092
1.71 8.311434933

I keep 2 decimal places; probably only 1 is significant. I just fired an e-mail off to BaleFire with these numbers too. If you guys want a properly updated spreadsheet I can provide it.

[lolito_fr]

Fascinating indeed.
MCW6000: multiply pumping power by 10 for a 1°C gain !
(but extremely good performance at low flow rates)

For the Nexxos & G4 the gain is roughly 3°C. Who said the Nexxos was better suited to a "low flow" system ?!

[pHaestus]

//edit: www.Madshrimps.be has made it so all referrals from Proforums get some "death to internet assholes" page instead of their NexXxoS XP review. I wonder why they post reviews if they don't want people reading them or talking about them?

I hope you didn't take that as a stab at you lolito_fr; was not my doing nor my intention.

[Cathar]

//edit by pHaestus: Madshrimps.be no longer allows referrals from this site. Instead they forward our readers to some page about gay men in musicals. This is causing people to be insulted on this site; I find this to be childish, pointless, and I suggest that, if it also upsets you, that you complain to the companies that advertise and sponsor their website.

LOL - Followed the link. Looks like someone is a little touchy.

[Cathar]

flow Storm G4
0.26 13.80666974
0.5 11.26556618
0.75 10.17413799
1.02 9.334698438
1.22 8.977748337
1.5 8.533861092
1.71 8.311434933

I keep 2 decimal places; probably only 1 is significant. I just fired an e-mail off to BaleFire with these numbers too. If you guys want a properly updated spreadsheet I can provide it.

Thanks for the numbers Ph. I think BalefireX may have gotten something mixed up. The interactive graph clearly ends at 1.85gpm, and not 1.71gpm. Actually in looking it over, it seems to be just the last segment between the last two plot points. Everything else looks okay. Everything up to 1.5gpm is okay.

Would it be possible for you to put a folder somewhere with these sorts of figures for each block tested? I'm very interested in doing performance vs power analysis for at least the top 8 to 10 blocks on the interactive charts (where I have pressure drop information available).

[Les]

//edit: www.Madshrimps.be has made it so all referrals from Proforums get some "death to internet assholes" page instead of their NexXxoS XP review. I wonder why they post reviews if they don't want people reading them or talking about them?

I hope you didn't take that as a stab at you lolito_fr; was not my doing nor my intention.

Not understand.
We were having a happy discusion(the odd dig) about Q*dP .
Why stop in it tracks.
A killed serious thread

[BalefireX]

Thanks for the numbers Ph. I think BalefireX may have gotten something mixed up. The interactive graph clearly ends at 1.85gpm, and not 1.71gpm. Actually in looking it over, it seems to be just the last segment between the last two plot points. Everything else looks okay. Everything up to 1.5gpm is okay.

That is what appears to have happened - don't drink and graph!

I've sent pH a new (and doublechecked) graph overlay

[Cathar]

Well it seems to be the time for people finding computational errors. I found one myself, and have re-plotted the graph. I'll add some more blocks as I go. Fairly confident this is correct now. Decided to remove the logarithmic axis. Although interesting, it places a lot of visual impact on the hydrarulic pumping powers that simply don't commonly exist (ie. <0.5W).

Edit: Graph deleted due to errors with best-fit smoothing algorithm

(sigh - I'll get it right one day)

[pHaestus]

I don't know what to say Les; I can't control what another website does. It wasn't specifically caused by this post though; it was I think in retaliation to the other thread about "what happened to the Nexxos XP review"

[pHaestus]

That's really neat Cathar. I am still trying to decide whether it's better or worse to try and explain hydraulic power to "avg Joe". Seems reasonable though. The G4 graph on the Pro/Testing page is fixed now; sorry for the error

[snowwie]

Why not just provide C/W per dP graphs? Given that, are C/W verses flow graphs even relevent? Its not like most people have any way to gauge flow, while their pump max head is published, and you can make educated guesses about what a radiator does to that figure.

it was my understanding that C/W per dP graphs were derived from dP per flowrate data

i dunno, just thinking of billa's work

[Les]

I don't know what to say Les; I can't control what another website does. It wasn't specifically caused by this post though; it was I think in retaliation to the other thread about "what happened to the Nexxos XP review"
pHaestus,
I apologize ,I was/am wrong.
I should keep out of the kitchen and stick to numbers.

[lolito_fr]

No probs here Ph, it seems to me that only you and Jaydee got redirected :D
(j/k of course)

[Les]

Edit: Graph deleted due to errors with best-fit smoothing algorithm

(sigh - I'll get it right one day)

Raises a smile.
Beermats still soggy here.

[Cathar]

I believe I've finally gotten all the bugs worked out of the procedure.

Even if nobody else really believes in this, I am gaining increasing confidence in it. The following graph's patterns mimics near exactly what I see/saw in my own testing with fixed power input fed to the pumps. There would naturally be some variations though between pump input power and hydraulic power depending on where one sits on the efficiency curve of the pump setup, so the correlation is not going to be perfect. I believe that this is the corrections that Since87 was trying to solve with his posts at OC.com.

In my own testing I'm using hydraulic powers from around 1W to 8W being fed to the blocks, although I guess that I really tended to focus on the 1.5-3W range when I look back at the work I've done and correlate it to hydraulic power.

Anyway, here's the updated graph that does contain some extrapolations to arrive at the 4W power figure.

http://www.employees.org/~slf/curves/pumps/power/perfpwr3.png

[Edit: New graph - more blocks]

[lolito_fr]

Nice! Hardly surprised to see the G5 is miles ahead ;)

Even if nobody else really believes in this
I certainly believe these graphs are much more meaningful than just C/W vs flow.
Flow is always only half the story...Your graphs give a true indication of waterblock efficiency (or is that efficacity?)

Looking back at Since87s' post, as I understand it, the purpose was for the tester to measure the blocks performance at one point - corresponding to a typical system flow rate. Maybe I misread it though...

BTW, I am now very curious as to how the "old-school" blocks would fair with this rating system?

[Les]

Fits sweetly with any of the old C/W v h plots
eg Fantasy (http://www.jr001b4751.pwp.blueyonder.co.uk/Fantasy.jpg)
WW3 (http://www.jr001b4751.pwp.blueyonder.co.uk/WW3.jpg)

Possibly indicating the importance of your attention to non-contributory power in the G series.

[pHaestus]

I'm going to quote this from the NexXxos XP thread to make sure the info doesn't get missed/lost and keep this discussion in one thread:

Ok, this is a continuation of Cathars' C/W vs Hydraulic Power graph idea, and some of the discussion above. (not porn related though :p)

I have decided to integrate the dT from the HE120.2 rad into my waterblock dT graphs for the Nexxos XP and MCW6000, so that, hopefully, the result is a graph of CPU-ambient dT vs water flow rate. *Cringe*

I used this rad mainly because Cathars' PQ curves for the Nexxos and MCW6000 already include the rads flow resistance (as well as 2m of 1/2" tubing).
The air flow rate corresponds roughly to 2 Papst 4312L @ 12v.

Power into the waterblock is 71W as per PHs' testbed, and this power is assumed to be fully dissipated by the rad.
Note that I have not included pump heat... will have to deal with that issue another day:)

http://img127.exs.cx/img127/573/componentdt.gif

http://img127.exs.cx/img127/6412/systemdT.gif

Also please consider this as strictly experimental :D

edit:
http://img130.exs.cx/img130/6114/pumppowers.gif
pH, where is the interactive system graphing tool? :cry: :dome:

[lolito_fr]

Thx pHaestus!

This is less relevant, but I'll include it as a logical conclusion.

http://img33.exs.cx/img33/6618/nexxus-mcw6000-pumps.gif

edit: and this one with added pump heat:

http://img34.exs.cx/img34/5439/nexxus-mcw6000-temps.gif

Eheim 1046, adds around 1.5W of heat to the loop
Eheim 1048, adds 3W of heat
Eheim 1250, adds 9W of heat
MCP600, adds 8W of heat
MCP650, adds 15W of heat


15W for the MCP650 sounds a little high(?)

[pHaestus]

You guys are too damn clever. Now I suppose all that you need is pressure drop numbers for all the wbs I've tested right?

[lolito_fr]

Now I suppose all that you need is pressure drop numbers for all the wbs I've tested right
You must be telepathic :)

If I was clever (or had a conscience...) I would have written a scipt in Matlab or better still created my own app in Perl ;)
As it is, it feels like I've gone the long way around to produce the last graph - bit of a half-assed way of doing things really. But hey, I may just have learned something on the way :D

[pHaestus]

Probably the other big thing to do is for me to put together a test loop that contains 2m 1/2" ID tubing, a thermochill 120.2 and the papst fans at 12v, and the blocks/pumps we are modeling. Use it to cool the test system I collected all the data on and we can see how closely the theory matches up with actual performance. Rather unexciting (the results SHOULD match up) but necessary I think. Can I find this radiator and fans in north america?

[nikhsub1]

Probably the other big thing to do is for me to put together a test loop that contains 2m 1/2" ID tubing, a thermochill 120.2 and the papst fans at 12v, and the blocks/pumps we are modeling. Use it to cool the test system I collected all the data on and we can see how closely the theory matches up with actual performance. Rather unexciting (the results SHOULD match up) but necessary I think. Can I find this radiator and fans in north america?
Not sure about the fans, but I suppose and fan with the same specs should do, the rad can be had at DD: http://dangerden.com/mall/Radiators/thermochill.asp

[pHaestus]

I don't see any of their canadian distributors stocking the thermochills. I guess I'll need to order direct from DD.

[nikhsub1]

I don't see any of their canadian distributors stocking the thermochills. I guess I'll need to order direct from DD.
You asked about North America? AFAIK, DD has an exclusive at least in the US on the Thermochill's. www.mountainmods.com has them too I believe (via DD). Ben Rising over at Mountain Mods is a very good guy.

[pHaestus]

I was looking at the DD resellers in canada for someone who might carry the thermochills. Figured I'd save on customs fees and shipping costs that way.

[pHaestus]

Joe just PMed me from IRC that the madshrimps people (jmke and liquid3d) have been banned from the forums and their IPs are banned from even viewing this site. I apologize for the interruption in this discussion earlier. Hopefully it won't happen again.

[Incoherent]

(from Nexxos thread regarding PQ) To do it properly you really need to measure it.

For a "ballpark" though. Classic flow mechanics tells us that the level of flow resistance is proportional to the flow rate squared (P = Q ^ 2). This doesn't take into account turbulence and boundary layer conditions though.

For a fairly decent ballpark equation to extrapolate from OC.com's results I've personally found that P = Q ^ 1.85 offers a pretty decent approximation across the typical range of flow rates seen in water-cooling. P = pressure. Q = flow. Not as ideal as having real data, but when given a single pressure/flow point like OC.com I personally found it to give a fairly close ballpark curve.

Re the P=Q^1.85 fit, I think there is a better way.

I assume you are familiar with the idea of a "k-factor", I stumbled across it recently when exploring the flow measurement problem.
Your PQ curves (http://www.employees.org/~slf/curves/pumps/xp-mcw6-gpm.png ) are not behaving, shouldn't one be able to generate a constant which, even allowing for transitions between flow regimes and boundary conditions, is relatively flat across flowrate?. I am getting this with measured data, (see attachment) it is constant enough that I would propose that every block has a "K-factor", a constant encompassing restrictivity described by the equation: K=Q/sqrt(dP) or P=(Q/K)^2, essentially the flow rate squared relationship. It's probably your curve fit that I am seeing, it is not generating a constant. If it is real, that's very interesting, there's probably a way to extract a Reynolds number curve from it.

Sorry if I am being disruptive, I have not been following this closely but I thought the K-factor thing might be relevant. It for sure is another way to generate a PQ curve from a single data point...

:)

[BillA]

(from Nexxos thread regarding PQ)

Re the P=Q^1.85 fit, I think there is a better way.

I assume you are familiar with the idea of a "k-factor", I stumbled across it recently when exploring the flow measurement problem.
Your PQ curves (http://www.employees.org/~slf/curves/pumps/xp-mcw6-gpm.png ) are not behaving, shouldn't one be able to generate a constant which, even allowing for transitions between flow regimes and boundary conditions, is relatively flat across flowrate?. I am getting this with measured data, (see attachment) it is constant enough that I would propose that every block has a "K-factor", a constant encompassing restrictivity described by the equation: K=Q/sqrt(dP) or P=(Q/K)^2, essentially the flow rate squared relationship. It's probably your curve fit that I am seeing, it is not generating a constant. If it is real, that's very interesting, there's probably a way to extract a Reynolds number curve from it.

Sorry if I am being disruptive, I have not been following this closely but I thought the K-factor thing might be relevant. It for sure is another way to generate a PQ curve from a single data point...

:)
yes, you are correct
I am in the process of converting all Swiftech flow resistance curves to a 'K-factor'

pH or Cathar
why not write an article on flow resistance characterization ? (yes, I'm lazy)

[pHaestus]

Bill I have a question about dP measurement. It seems to me that the easiest way to deal with all the different possibilities of tubing and fittings and such is to:

1) zero the xmitter
2) Run a length of the tubing to be used over the flow range of interest (blank)
3) Cut the tubing in half, mount block/rad, and repeat (sample)
4) sample - blank = dP of only block/rad (this takes care of the dP of crosses and fittings and tubing and all leaving only wb).

Is that unnecessarily complicated? I was concerned that the friction factor of clearflex or silicone would be difft enough from copper pipe to make doing a calibration with just copper pipes of difft ID to be a mistake.

[Cathar]

Hmmm, maybe some of you more engineering types could help me out to understand as I may have the following wrong (being self-educated and all on this stuff):

P=(Q/K)^2

seems to me to be simplification of Bernoulli's equation. However if we consider viscous head, being the energy that gets lost as heat (and absorbed into the liquid itself), then for turbulent flow the friction co-efficient of the viscous head term will fall away as the Reynold's number increases (which is proportional to the flow rate).

So what we then have is an effect where P=(Q/K)^2 isn't really followed cleanly. For the more restrictive blocks I intuitively would have thought that they would deviate even further from the classic P=(Q/K)^2 equation.

Now, quite true, Bernoulli's viscous equation consists of two primary terms, being the constant head loss due to inviscid flow (which is proportional to the flow rate squared), and the head loss due to viscous flow. The relative effect of viscous flow term diminishes as the flow rate increases, meaning that we end up with a curve that doesn't fit P=(Q/K)^2 any more.

I threw out P = Q ^ 1.85 as a really quick and dirty approximation of this effect, perhaps only valid for within 0.5 to 2.0x the data point given at somewhere like OC.com.

I measured various data points from 2.0 - 5.0LPM for the Storm/G4, and it didn't seem to me to quite follow a simple P=(Q/K)^2 curve.

That could also just be due to measurement error too.

Or perhaps one of you kind lads could tell me if viscous flow effects don't even apply here?

[BillA]

nothing is too simple once one gets into it

- the dP units are temp sensitive, if not temp controlled you'll need a zero reading at the start and end; use this to 'correct' the dP reading
(I would not suggest re-setting the zero, this is part of the unit's cal)

yes, your procedure is correct
I lay out the crosses flat on a table and connect them with a short piece of tubing, run a dP curve, then cut that tubing in half to connect wbs; then the single connection loss can be deducted from the wb reading at each flow rate

but you need to do this for each tubing size you will be testing with

[pHaestus]

What about the fact that the tubing has a curve in it when the wb is connected, but is straight through w/o the block?

[lolito_fr]

I threw out P = Q ^ 1.85 as a really quick and dirty approximation of this effect
Isn't that the same law used by the Hazen William equation?

[BillA]

What about the fact that the tubing has a curve in it when the wb is connected, but is straight through w/o the block?
nooo, the cross must/should (?) be close coupled to the wb/rad and that connection tube kept straight
- a bend will have an effect

[Uncle`BuZZ]

In MY opinion, the solution is to produce C/W vs flow data and dP vs flow data for waterblocks and a few common radiator/fan combos. Then to use that data along with the other components in the loop and the pump P-Q curves to predict a final C/W for the system. That is what groth was going for here:

http://pages.sbcglobal.net/water.groth/Dorky%20process1.htm

The interface would have to be simplified a lot and it's awaiting my dP vs flow data...

It's waiting on my dP vs flow numbers to be generated; that's next up after this Alphacool nexxos XP review is done

I think we tried to do same thing in different way...


you can found my solution (version alpha) here (http://pagesperso.laposte.net/unclebuzz/watercooling/) (in french). I stopped development cause I miss data to put into my db...

you can define your loop with some tubing, radiator and waterblock, in series or what you want, you just need to drag elements where you want on the loop and see results...

You need the JVM from SUN and not the JVM from microsoft to use it. You could see some difference from your results because I probably haven't the same data of you (very few data in fact) but they should be minim.

In my dream I hoped to add some C/W data to do a prediction of performences, but I miss drop pressure data, so I don't imagine having enough C/W data... :shrug:

[pHaestus]

I am happy to open source all data. Let me get it in a reasonable format. I suspect dP vs Q numbers will be more useful to others and I'm in the process of fiddling w/ that now

[pHaestus]

Danger Den most graciously sent me a Thermochill 120.2 radiator (thanks guys!)
I will buy some Papst fans (anyone have a source for the ones used in these simulated loops?) and then try to reproduce some of the dT vs pump results using our modeled cooling loop.

[BillA]

good luck
correlating that systems stuff will be a chore, you'll have no 'free' time this xmas

[pHaestus]

I am a dummy. Danger Den had the 4312L's in stock; should have gotten them to drop a few in the box. I ordered them just now and should have them next week.

I'm in research scientist mode still: NO correlation is still worth knowing right? LOL

[pHaestus]

OK I am setting up the thermochill-based test loop tonight when I get home. I'll post an update when I get it running. The New AMD64 system I built for general testing will allow me to keep using my TBredB box for interesting stuff like this I hope.

[MaxxxRacer]

dont kill the winnie man...

[plywood99]

OK I am setting up the thermochill-based test loop tonight when I get home. I'll post an update when I get it running. The New AMD64 system I built for general testing will allow me to keep using my TBredB box for interesting stuff like this I hope.


Hope this hasn't died down. Looking forward to the results...

[YEP]

You guys are too damn clever. Now I suppose all that you need is pressure drop numbers for all the wbs I've tested right?

Not to be rude ..... sure "buddy"

This thread is really really nice. Good work you guys are doing.

When putting a new system together it's reall nice to have an idea how much pressure drops across a waterblock.

Again invaluable work you guys are doing for the community

[bobo5195]

Nice work, the computer model saves me answering many questions.

I havent been able to find this information anywhere else:
What are the assumptions in the model though.
Is the friction from the pipe based on tubulent or lamina flow and is the small diameter and possible boundary layer problems consider (ie has boundary layer thickness been considered as a check).
When comparing different widths of pipes is the head loss coefficent from varying diameter considered. For example thermochills are 3/8ths but piping might be 1/2 (this might be taken into account by bills testing) and the inlet and outlet to blocks or pump.