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Water Block Design / Construction Building your own block? Need info on designing one? Heres where to do it |
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02-20-2004, 07:15 AM | #76 | |
Thermophile
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02-20-2004, 07:35 AM | #77 |
Cooling Savant
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I must have been using the dimensions for the later batches at 2 lpm.
I'm not sure when I'll be able to get to a scanner so I took a photo of it with my phone. Sorry for the poor quality but it is just about readable |
02-20-2004, 10:05 AM | #78 | |
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You chaps obviously have to much time on your hands to post so much or are hopless addicts as I am Discussion about jet sizing and distancing pontificates over 'How to obtain trully turbulent flow' age old cooling dilema. Reynolds number tells us if liquid flowing over surface (pipes in our cases) is turbulent or laminar. We want truly turbulent. Reynolds number is proprtional to Velocity and specific lenght L (pipe diameter here). We obviously cannot increase pipe diameter as much as coolant's velocity so we go for the latter. To obtain truly turbulent flow we need Reynolds >4000 ( reference here ). The whole reason for turbulent flow is to make as many water molcules get in contact with 'sticky' layer as possible and to reduce boundary layer thickness to minimum (Fourier's Law of conduction Q= k*A*dT*time/d, where d here is thickness of boudary layer and Q energy transferred). Jet impigement system substitutes for larger heat transferr area limited by dimensional constrains here. Does it make any snense? |
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02-20-2004, 10:26 AM | #79 |
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Today I have too much time on my hands and I'm a hopeless addict I've been sitting around all day taking far too many temp measurements. I have 9 different combinations of blocks to test and I'm almost halfway, after pretty much a solid week of testing. I don't have any lectures at uni on a friday so I've spent all day sitting at the laptop updating my spreadsheets as my test continues.
There is a bit more to water jet impingement than whether or not the flow is turbulent. It is highly likely that the flow is turbulant anyway at lower reynolds numbers. You need quite a long, extremely smooth pipe for the flow to become turbulant as high as 4000. As soon as the jet exits into the surrounding water it will become increasingly turbulant the further it travels through the surrounding water. However the centerline velocity of the jet reduces the further the jet travels through the surrounding water. These two elements (turbulence and centerline velocity) are the key ingredients to impingement cooling. So basically, the further the nozzle exit from the base plate, the greater the turbulence and the closer it is the greater the jet velocity. So it is a case of balancing the two components to give the optimum heat transfer. But now I'm off to the pub Typical student |
02-20-2004, 03:35 PM | #80 | |||
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02-20-2004, 03:57 PM | #81 | |
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I have modeled the impingement mathematically and have been over it and over it. I won't sit here and go through it with you just for your proof as I assume your just as well versed in it as I am. Neither will I play the "Who's smarter or better" game. Base plate thickness is just another variable in the "whole picture of the block" that one can tailor to benefit the impingement you have. Design the impingement based on the flow/velocity/pressure and use baseplate/furniture to benefit that. With all the different systems and flow rates, the problem becomes unsolvable mathematically - I agree. What it can do is get you somewhere close with the constants you have as a reference point to work from. |
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02-20-2004, 04:07 PM | #82 |
Cooling Savant
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Ultimate Fluid Physics & Mechanics
I've just found this
I think it presents all basic theory in quite simple way. I am spawnig some ideas of how to improve jet design but atm most o them are too expensive to produce (to complicated to machine. I am off to produce some 3D models to show you |
02-20-2004, 04:25 PM | #83 | |
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What would be interesting is to try a capillary tube design in an array that would benefit pelts but be interchangable plates to use in a IHS design. Machining that would be a nightmare though. I'v got a decent design in the works using that idea but you can forget using any pump less than a L30 or equivilent as it restricts flow to much. Not to the mention the amount of drill bits I killed. Now if i had access to a laser. Intel has a good white paper you might be interested in also. If I can dig it up again from them I'll post a link to it. It's an interesting read. |
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02-20-2004, 04:37 PM | #84 |
Cooling Savant
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Here's something that migh catch your eye Cathar. Check out the chapter called "MICROPROCESSOR POWER AND HEAT FLUX TRENDS"
http://www.intel.com/technology/itj/...cles/art_4.htm |
02-21-2004, 07:15 AM | #85 |
Thermophile
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Ignore this
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02-21-2004, 01:30 PM | #86 | |
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He He He I hope you managed to get yourself properly pi$$ed m8 I used to have my best ideas after two,three tumblers of 18 year old highland single malt Anyways, what I meant in my post was that turbulence and turbulent flow causes boundary layer to thin down. Jetted water stream is exerting additional localized high pressure causing further thinning of boundary layer over small area (cup). The overall goal is to make boundary layer as thin as possible to achieve otherwise unimaginable conductive heat transfer coeficient (sp?). Optimal distance between cup and nozzle is dependant on nozzle diameter and jet stream velocity. Water exisiting nozzle is shapad like paraboloid function graph due to simple fact that middle of the stream is the highest velocity and the closer to nozzle wals the slower water travels beacuse of friction (viscous) forces (again boundary layer effect). Adjusting distance tries to aim 'peak' of the jet before it starts to turbulate (jet is and must be as laminar in it's flow as possible to obtain the highest speed). The biggest problem with jet design is that it's peak working paremeters windows is quite narrow and that's why Cathar is designing his blocks for certain flow range adjusting z/d accordingly. Imho that's all what could be possibly done in this area. Looking at the equation I wrote earlier one can clearly see that the next step is to fight for bigger surface area and this is the biggest challange here. Production costs (there are many designs which are MUCH more effective but are exorbitantly more expensive) versus performance ratio is the killer here. Who in his right mind would pay £500 for water block??? I only spent 15 mins on 3D model and it's not yet presentable but I just thought about a clever way to make it feasible to mass produce. Unfortunately it is going to be yet more expensive than Cather's baby... T'nite I hope to post my model for you guys to check out and beat the living daylights out of my design |
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02-21-2004, 01:38 PM | #87 | |
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The coldet spots are cache areas (memory as we all know do not heat up much). The rest is a mixture of controllers and logic arrays. Well, the best idea would be to have silicone sandwiching layer through which w could pass veru low energy atoms on much smaller than copper size creating effectively in-die nano cooling solution (quite similiar to Peltier Effect ) |
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02-21-2004, 03:59 PM | #88 | |
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h=151.44Re^0.623 for calculating a convection coefficient for 1mm nozzles in a dashpot(bowl or channel urinal). This generic suggestion is most probably incorrect.However finding an alternative may be difficult and without a reliable estimate of h all CFD(or any other) modeling is completely useless. * From here Edit(very late): Mis-read my own graph. Corrected h=263.66Re^0.643 to h=151.44Re^0.623 Last edited by Les; 06-28-2004 at 01:19 AM. |
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02-21-2004, 05:21 PM | #89 |
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Les, when stating h, and the area associated with it, what are you defining as the area? The area of the heat source? The convectional area? The "net effective" convectional area?
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02-21-2004, 05:47 PM | #90 | |
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Edit. In the WW case the considered area is within d/5(ish, ish) of the die area. Would tentatively suggest that Impingement is only a special case of a vectorial change in coolant velocity. Last edited by Les; 02-21-2004 at 06:07 PM. |
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02-21-2004, 07:19 PM | #91 |
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Design improvement
As promised some piccies and explanation.
What I was aiming at was increase of area and actually some increase in pressure (velocity) due to maintained (roughly) cross sectional area after stream leaves nozzle. Apologies for crappy quality of renderings due to lack of time... It's only schematic for starters. Red stuff represents blocks base, blue are nozzles and greyish bits represent my 'innovation'. TOP VIEW LEVEL VIEW Last One The only problem is in manufactruing the damn thing. One could machine it form one piece of copper but costs probably would be greatly prohibitive. Then I thought about drilling hole for each pin. If nozzle is 1mm dia and is spaced by 2mm from each other then pins could be 2.5mm in dia if conoidal or 2.5 square base tapering to a point, which is much easier to make - just take 2.5mm dia hard copper or brass wire , grind it to shape leaving around 3mm for thread at one end, cut thread and screw it into ready threaded hole in baseplate. What do you think? |
02-21-2004, 07:24 PM | #92 |
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Les, I always thought that we are dealing here with conductive energy transfer, not convectional (vector oriented, usually in static flow, or totally static conditions, in liquids that is) thermal energy transfer.
I may be totally wrong here since I only atrted doing this stuff recently |
02-21-2004, 07:38 PM | #93 | |
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02-21-2004, 11:22 PM | #94 |
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Nice design indeed.
The pins act as the required fins, and there's still an inpingement effect on the baseplate and, to some extend, up the sides of the pins. But the proportion of those pins leave a much smaller "fin equivalent". The "Cascade" being the reverse design, the fins are more massive, in higher proportion, and most important: connected. I'm sure it would be an excellent performer, but I wouldn't bet that it would beat a Cascade just yet. The main issue I see is that by reversing the design, you have the incoming flow interfere with the second inpingement effect, and adding an almost useless laminar flow parallel to the pins. The secondary inpingement may also end up forming on a plane perpendicular to the baseplate, between the pins, which would be another loss of pressure, without any thermal benefit. On a scale so small, I'd consider press fitting the copper pins into the baseplate. Got an Enermax around the shop? |
02-22-2004, 12:32 AM | #95 | |
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After some testing, I'm seeing basically at least a full 0.5C improvement with the Iwaki MD30-RZ pump, which I guess is about as much as I would expect. Re: the XXX. The program is written up and I fixed/tweaked a few things. The machinists won't get time to run until about 10 days away, and even then it's a "maybe". They are being pretty nice to me with the prices they're charging so I can't complain too loudly if higher paying customer jobs hold things up a bit. |
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02-22-2004, 06:24 AM | #96 | |
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02-22-2004, 06:33 AM | #97 | |
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Mind you, the MD30-RZ was already pushing about 10LPM (~2.65GPM) through the complete system without the restriction plate, so there's not much correlation that could be drawn with Phaestus's results. |
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02-22-2004, 06:38 AM | #98 | |
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