Actually, I think I was at 97.7% (1.6 from 70W)... ;)

It is relevant to calculate the heat induced by the pump, or more specifically, the heat induced by the flow restrictions.

As Since87 demonstrated, it can be easily calculated.

Flow restrictions shouldn't add to much if any. Unless it's a very strong head pump or the restrictions are so great it causes pump cavatation.

I assume that you mean while using a pump that has VERY little head to work with. And results don't hold up to your statements. Cathar's WW is a 'high' (relatively) resistance block with results to challenge just about everything (low resistance) out there.

I do agree that your not measuring cooling power, rather the power used from the pump's output.

Submerged Liquid Jet Impingement Heat Transfer(SLJIH)

The only submerged jet data with which I have played are presented http://widget.ecn.purdue.edu/~eclweb/jet_benchmark/ in the "Heat Transfer Results as Excel spreadsheet".
I do not offer a graph because of "Any unauthorised use, copying or mirroring strictly prohibited ".
However the graphs show the Heat Tranfer profile changes with conditions.
However I do ,naively, consider the "plateau profile" of the "3.1mm ID" results maybe the ones applicable to to flat bottomed wbs.Additonally in "fantasy calculations" I equate the "h" of the plateau to that calculated by Flomerics at r= ~2.5D.
Yes, it is "stretching it a bit" but ......................

Murray13 is right here.

This is where you want to look at your pump's PQ curve. If you were running under the peak efficiency, then a higher restriction would yield better results, because you would then have more total power applied by the pump.


I found out something interesting the other day, while looking up orifice plates for LiquidRules: there are two kinds of restrictions out there; those that provide a recoverable pressurre drop (venturi) and those that don't (orifice plate). Jet inpingement produces a non-recoverable pressure drop.

What that means is that although the fluid is flowing at a higher speed, it is permitted to enter an open area, in which it will turbulate: this speed cannot be recovered, it is simply a result of the opening. In a venturi, the speed is (essentially) recoverable. (Venturi is like a couple of funnels connected together at the small end).

Ben, I've neither directly spoken with nor seen a picture of BillA (other than that X-Files spoof), but I gotta believe it's statements like this that make him shake his head and ride you hard. Technically there is no zero-loss device, though smooth transitions have lower losses than others. You've been making thousands of posts here and elsewhere about "theory" and you just figured this out "the other day"?

Well, at least I got a good chuckle on a Saturday morning. Thanks. ;)

I'm glad I could liven up your morning:D

I just mentionned it, because I hadn't seen it anywhere, and because I never looked at it that way before. It was specifically about recoverable vs non-recoverable pressure drops. The friction losses are an add-on (where it applies).

It might not be relevant to anything, but it's there... It also relates to Radius, as I'm looking at trying to implement a jet (or jets), but my solutions always seem to end up into (mostly) recoverable PDs.:shrug:

Try a pump with a stronger head. I just got done trying out my new block with a single 1/16 jet. It simply was to restrictive for the pump. 1/8 seems to be the limit for my pump. 3/16 is ok with 1/4 being a little to much. So anything between 1/8 and 3/16. With multiple jets, the total orfice area of the jets has to be within that 1/8 to 3/16. Doesn't give you much to play with but your limited to the head of the pump which isn't all that great with these aquarium pumps.

I like to try a Iwaki (that the name?) with a nice head that uses about the same amount watts. When I tried the faucet trick that had about 50 psi and the same constant water temp as ambient air , the gains were great with a 1C difference between idle and load. Total 5C delta. Finding a pump like that without putting it's heat into the water to negate the gains is probably impossible.

Not really SysCrusher. If you can only go down to a 1/8 single jet because of lack of head you will not be able to go smaller with multiple jets. Hydrodynamics rearing its ugly head again.

I don't understand why. If the total pressure and velocity of the smaller jets was equal to a single jet with the same pressure and velocity, wouldn't the two be the same? I must be missing something.

I have no interest to use multiple jets. Over a wider area of heat it's great. To cool an area the size of a cpu die all is needed is one single impingement. Once one tries to use multiple jets so close together, it effects the wall flow and possibly the stagnation area.

Maybe relevant:
Some rough sums:
http://www.jr001b4751.pwp.blueyonder.co.uk/NozVel.jpg
Based on Billa Data extracted from GIF* by Inspection and using :
http://www.jr001b4751.pwp.blueyonder.co.uk/NozPQ.jpg

* http://www.thermal-management-testin...vs.%20flow.gif

I caught that, thanks.

I've got a Little Giant 2-MDQ-SC, that has a max head of 14.6 feet.

The problem I'm encountering is a dead flow spot in the block. I'm aiming for a jet, but of course because of the unusual inlet geometry, I have to tune it all just right, to maximize what my pump can do.

I ran some tests with my pump, where I cap the outlet with caps with different size openings. I was originally shooting for 3/16. Right now, I'm looking at 1/4. I also tried a 3/8 test.

None of my tests were conclusive. Part of the reason is the calculation (missing measurement?) of the pressure drop. I also suspect that the pump is behaving erraticly, because it has a design limitation (i.e. it doesn't do 0 head), or maybe I'm just completely wrong and nothing has anything to do with anything...:shrug:

See LiquidRulez thread for a bit more info.

only to those who cannot connect the dots
a (repeat) gift for the 3432 count poster

this is how pump 'data' is commonly presented (w/o a curve)

http://thermal-management-testing.co...60~%20data.jpg

but if you think BACK to the pump characteristics link in pHaestus' article, you might recall a discussion of pump (impeller) efficiency
do you know what that means ?
here is more complete data for the same Hydor pumps (but 50~)

http://thermal-management-testing.com/hydor.jpg

do observe how the min-max ratio changes as the pump size increases
getting a clue yet ?

Thank you Bruce at Cooltechnica for the pumps

"Other ways of shooting a liquid"

BB2k posted the above line and I would like to expand on it.
In some experimental data I ran across there was indeed a difference in the results of jet impingement on a flat plate by changing the shape of the nozzles (circular being among the worst). Another variable to the equation. Anyone feel like googling?

google ? google ?
who dat ?
whey dey at man ?

what I wanna know is . . . .

Les, that's true if the id stays the same. Sure, you will lose velocity and pressure the more .25 id holes you have. If you smaller holes to equal the same pressure and velocity of one .25 id hole, their the same not including geometry.

Because it changes the size of the stagnation point with a circular shape being the smallest. Also a flat plate isn't as good as a concaved plate. Another one to add to the equation. The wall flow and film is the hint.;)

EDIT: The shape also effects the spreading rate and turbulance levels.

The pump may well do a 14 foot head but try to get a 14 foot head with a 3/16 id hose. Does that pump have the required pressure to push the water now in the same distance? It's the limitation of the impeller called back pressure.

Here's a link courtesy of myv65 that was imformitive for me about pumps.

Without accurate data would not like to add to further to my "evasion".
Have found trying to estimate dP in different ID nozzles beyond me.
Will leave the "evasion" posted - graphs quite pretty(and maybe informative


Would be most interested in any links to any of this work.All are intuitively attractive.

I've had that dP kindly calculated for me (see details in Radius thread). I can share this formulae with you (or try to post it here, PM me).

Calculations were based on fluid properties, flow rate, and nozzle size. Results include dP (and speed?).

I was also kindly reminded to look into hypersonic (or was it supersonic) flow speeds... (I was assuming 4 gpm:rolleyes: ).

I'm assuming that you're not trying to imply that the pump's behavior does not correspond to it's curve.

I simply used a bucket of water at the inlet. Granted that there was a 1 foot rise, but I honestly expected the water to shoot up 15 feet, not 10. I have to revisit that test sometime, and see how I can get it right :rolleyes:. I know that my previous calculations were wrong.

That's ok Les, I understand. I'm not here to belittle anyones education or way of thinking but to discuss and learn something new from what data that is present.

Here's some links.
An impingement database but you have to pay. Why? So I can't link to any information.
http://www.eevl.ac.uk/jet/index.htm

Various links I collected.
http://www.electronics-cooling.com/h...01_may_a2.html

http://home.icpf.cas.cz/vejrazka/web...ew_booklet.pdf

http://web.cvut.cz/cp1250/fme/k212/p...ta/h06%5Ea.htm

http://www.stanford.edu/~xzm/Research/Reno2003.pdf

http://widget.ecn.purdue.edu/~eclweb/jet_benchmark/

http://fcl6.kaist.ac.kr/people/phd/pts/article.pdf

http://216.239.57.100/search?q=cache...n&ie=UTF-8</a>

Calc to calculate heat transfer of impingement. No idea how accurate it is.
http://www.coolingzone.com/Content/D...as/fcalc10.htm

Then there is the libraries but you have to pay for each copy of an article. Their more informative than these links. What ever happened to free imformation via the internet for the people?

Ben.
Thanks for the offer.For the moment, further dP sums are not on my agenda so will give a miss.

SysCrusher.
Thanks. 50% are new to me.
As you are aware, I have used and abused the the Flomerics calculator for both Cathar's WW* and the Switech462**.
I do get reasonable( my opinion) , if accidental, agreement with Billa's test data.

* http://forum.oc-forums.com/vb/showth...hreadid=161563
** http://forum.oc-forums.com/vb/showth...hreadid=161124

No, not quite. If the ID stays the same and you add more holes of the same D then the pressure drop will be the SAME. The flow rate (gph) will increase.

You can NOT decrease the diameter of the opening with the same pressure.

I'll chew on this one for awhile. I "think" I see your point but still I don't see the logic in it.:confused:

Here's another link Les. It challenges what I said about multiple jets in a previous post. I just might try it once more and see what results I get. I'm quite interested in this impingement. I believe with a well designed impingement one will get results that rival micro-channels.

http://micromachine.stanford.edu/~lian/jetcooler.html

Here is a cut and paste from a publication. The author is in the paste so it should be alright to post it here.

Quote
"Article number: 1321
Title: Effect of nozzle geometry on impingement heat transfer distribution from jet arrays
Author: Owens,R.D. and Liburdy,J.A.
Year: USA, 6-8 August, Vol. 1, ASME HTD 303, 3-10
Abstract: Heat transfer distributions were determined for flat surfaces using three different 3 x 3 jet-impingement arrays. Each array used a different jet orifice cross sectional geometry, either circles, triangles, or ellipses. For each geometry, the jet-to-jet spacing divided by the hydraulic diameter, was three. Five flow rates were tested with Reynolds numbers ranging from 268 to 1557. For each flow rate, the four jet array height-to-jet spacings (H/D) of 2, 3, 4, and 5 were tested. All of the parameters presented, such as the Reynolds and Nusselt numbers, were based on the orifice hydraulic diameter. In order to determine the heat transfer distributions for each condition tested, thermochromic liquid crystals were used as part of a transient heating test method. In the majority of the tests, the ellipse array performed the best, with the triangular orifice close behind. Also, of the three orifice geometries, the ellipse had the lowest pressure drop. The heat transfer improvement was especially predominant at low Reynolds number.
Publication: Proc. 30th 1995 National Heat Transfer Conf., Portland,"
End quote

Click to jet impingement database search engine

I'll dig some more. I recall reading a strange phenomena with the ellipse. It (the jet profile) will invert itself on the impingement surface at the right conditions for a benefit in heat transfer.

All right.

I found my other source of "confusion".

When designing/calculating a nozzle within a pipe, the formulaes used assume that the distance passed the nozzle is at a minimum of 10d.

So I now conclude (incorrectly?) that the pressure drop in a jet inpingement configuration is composed of 2 things:

a)pressure drop across the nozzle

b) pressure drop caused by the jet striking the baseplate.

Now is there actually a pressure drop from [b], or is this configuration merely affecting the nozzle's performance, throwing off any calculations? If there is a pressure drop, is it calculable?

The easy answer is that "yes", the baseplate will have an effect at the velocities and gaps we operate within. The tough answer is determining the effect. There is no analytical solution, only simulations. Accurate testing is the best bet.