Watercooling a normally air cooled part? - Page 1
Forum section: electronics / projects

author: Marsupilami
author_rank: Frequent Contributor
timestamp: June 23, 2023, 05:39:59 am
content: Hi Folks,A new project plan is forming in my head and I'm looking for ideas.I wonder if there's any feasible way to take a normally air cooled assembly and turn it into water cooled. Utilizing the now mainstream gaming PC watercooling infrastructure.I can't submerge it, so that's out.One idea I had was to take the aluminum heatspreader/heatsink part (more like parts) of the enclosure and mill it flat, removing most of the fins and put a regular waterblock on it. The difficulty in this is the complex shape of the heatsink and it requires full disassembly of the unit.Another though I had was, what if I could squeeze copper pipes between the fins and fill up around it with a foamy thermal compound. (E.g. Laird TPutty ?)Like this would fit right in there between the fins.I wish there was some sort of flexible hose for liquid cooling that expands into the space when under pressure thus making larger contact surface.The idea is to have the same cooling efficiency without the need to have an air intake and exhaust, but I don't have experience with liquid cooling so I don't know how much contact area do I need to achieve the same heat transfer.What are your thoughts?

author: Berni
author_rank: Super Contributor
timestamp: June 23, 2023, 06:03:28 am
content: Id say you could get very good thermal contact if you find a copper tube with the diameter that matches the radius on the bottom of those fins. Lay the tube in and use a press or hammer with a appropriately shaped tool to force the tube to conform to the shape.If you run the tube up and down the heatsink a few times there should be plenty of surface area. You could also put a little bit of thermal paste down under the tube to improve the contact.

author: Terry Bites
author_rank: Super Contributor
timestamp: June 23, 2023, 10:44:23 am
content: I did something like many years ago and it worked ok.I used soft copper refrigeration tubing and bent it up with a semi rigid coax tool.I forced it into place with copper plate strips on the top and sides, then bolted on a second heatsink force it down.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 23, 2023, 11:49:33 am
content: If you have milling machine then surely you can mill your own copper(?) waterblock and attach the components to it directly?Making the microfins is out of question I guess (probably need skiving machine). Meander maybe enough however.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 23, 2023, 08:02:14 pm
content: Yeah.If the existing heatsink has heatpipes, you could consider cutting the heatpipes open and using them to circulate water.Those heatpipes are usually hollow and filled with some gas. But they are pretty narrow and not optimized for circulating water, so I don't know how well it would work. Could be worth a try.If you want to see how these work:

author: jbb
author_rank: Super Contributor
timestamp: June 24, 2023, 02:56:12 am
content: Cover your eyes, folks. This is about to getugly…How about putting the air-cooled thingie in a box with an air-water heat exchanger and a circulating fan?

author: coppercone2
author_rank: Super Contributor
timestamp: June 24, 2023, 03:04:43 am
content: if you cut off the fins, cut round grooves for the pipe, and smush it in there with epoxy ,it will be similar to a commercial cold plate.otherwise you need to take off the heat sink, fly cut it, and then bond a cold plate to it.

author: CosteC
author_rank: Regular Contributor
timestamp: June 24, 2023, 09:39:07 am
content: You maybe can submerge it in transformer oil. Very efficient cooling. Not nice to retrieve from oil.Silicon pipes can be so thin they will expand under pressure, yet controlling this pressure is tricky.Air-water-air cooling usually is not super efficient, but popular, especially in enclosed cabinets in harsh environments.Maybe its enough to put relatively thin walled plastic piping in heatsink as per initial idea? With relatively fast flow thermal transfer shall be very good.

author: Ian.M
author_rank: Super Contributor
timestamp: June 24, 2023, 11:11:06 am
content: The problem with all the direct liquid cooling solutions so far except CosteC's transformer oil suggestion is that they don't provide any cooling for unheatsinked parts relying on the air flow through the heatsink. Rather than use transformer oil I suggest immersion inFluorinertor similar, that is less problematic to clean of boards for servicing, with a water cooling coil in the bath in close proximity to but above the board to maximise convective heat transfer.Alternatively, as Jbb noted, sealed air to water cooling could be provided for the unheatsinked components, but it would be advantageous to convert the heatsinks for direct water cooling.

author: Marsupilami
author_rank: Frequent Contributor
timestamp: June 24, 2023, 08:24:07 pm
content: Thanks all,I was leaning towards milling the fins off, but then I disassembled a unit again to see what's underneath and I'm not sure I could put it back together with the gaskets and thermal paste that's already there and it's out of the question to mill it with the circuit board attached.As I said I can't submerge it either. The heatsink is not continuous and there there's IO on every possible side so sealing that off would be a nightmare.This is how one sections looks like and what I was thinking of doing with it. It's the most critical part with a Virtex 6 FPGA right under.The fin spacing is 4mm, which would fit 4mm copper tubing perfectly. Square tube would be better for more contact with the fins but that's harder to find. I would use foamy thermal paste to fill the gaps.Maybe machined pieces are on the table too for the individual loops between fins.Let's say I have that figured out, the next question is how to hook all of these up. Ideally I could find a small enough fitting that I can thread into the end of each loop and have a bigger distribution block wherever I have the space for it. 3mm 1/8" OD liquid fittings, anyone?

author: CosteC
author_rank: Regular Contributor
timestamp: June 24, 2023, 08:37:04 pm
content: Quote from: Marsupilami on June 24, 2023, 08:24:07 pmTo seal it one need to seal only cables, which is not hard if you do not need to keep it pressurised.Not sure what power levels are present on mentioned Virtex part. You can press copper piping between fins and joint it to rest of system with elastic tubing.You can shave fins off and glue copper to aluminium with thermally conductive epoxy (easy but not super effective).

author: langwadt
author_rank: Super Contributor
timestamp: June 24, 2023, 08:46:28 pm
content: Quote from: Marsupilami on June 24, 2023, 08:24:07 pmif you anneal copper it is very soft, you could probably squash 6mm tubing into the 4mm slotsI'd just do two big loops to get a bigger bend radius and solder the ends together

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 24, 2023, 09:58:21 pm
content: Quote from: Marsupilami on June 23, 2023, 05:39:59 amWhat's the problem with disassemblying it? Is it a computer from the Apollo or what?Just do it in the right way, piping it from the outside will be a mess anyways!

author: Berni
author_rank: Super Contributor
timestamp: June 24, 2023, 10:29:28 pm
content: Since you have a milling machine you could easily create a tool that has a shaped channel like the one in your heatsink and another tool that presses a oversized tube down in it, forming it into the square shape. Copper is rather soft, especially when annealed so an aluminium tool would still easily form it. Once you pull the tubes out of the tool you have them formed with 2 parallel flat walls that perfectly fit the gap between your heatsink fins.To then join it all up just drill some holes in a larger copper pipe, stick the tubes in, and solder them.

author: jbb
author_rank: Super Contributor
timestamp: June 24, 2023, 11:02:33 pm
content: If you go ahead with pressing copper tubes into the heatsink, I suspect that the ‘bottom’ layer of tubes will do most of the work. So there may be little improvement from adding a seconds ‘top’ layer of tubes.

author: langwadt
author_rank: Super Contributor
timestamp: June 24, 2023, 11:52:47 pm
content: Quote from: jbb on June 24, 2023, 11:02:33 pmyeh the top layer would be mostly redundant

author: Marsupilami
author_rank: Frequent Contributor
timestamp: June 25, 2023, 01:01:46 am
content: Quote from: DavidAlfa on June 24, 2023, 09:58:21 pmNone of what I intend to do is the right way.It's not from the Apollo but it's an off the shelf product. I'm not certain if I remove the main heatsink/shield I can put it back well enough not to affect heat transfer from the board to it and also EMI and whatnot.The perimeter gasket and the inside thermal interface is all printed / dispensed. Other than that I agree, it would be the cleanest / most elegant.

author: Marsupilami
author_rank: Frequent Contributor
timestamp: June 25, 2023, 01:05:31 am
content: This coiled up think looks interesting.The reason for the top tube is not more heat transfer but so that I can press the think in from one end, but that might not be smart due to not being snug enough anyway.

author: Marsupilami
author_rank: Frequent Contributor
timestamp: June 25, 2023, 01:16:37 am
content: Hmmm...Pipeshttps://www.ebay.com/itm/183526176798and shimshttps://www.ebay.com/itm/173630803833