Project: Hush! - updated 26/12/23

mjones1 said:
Great work you have done there.
How are you going to get rid of the burnt marks on the copper?
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Well it's a combination of oxide and burnt tacky flux - it seems to go after a long time in the acid bath, but failing that I may be able to clean it with a large ultrsonic cleaner my brother is planning to get. I say maybe as the dimensions of the internal tank of one is 395mm wide x ~540mm x 300mm deep, so would be a very tight fit indeed to clean all of it. The other he has his eye on is larger and wouldn't be a problem getting it inside. They're very good at cleaning:

 
Not that much progress - i've been away work shadowing for 2 weeks so haven't been able to get that much done since the last update - I'm up to 34 fins soldered on, so around halfway through atm. I wasn't happy putting it in the acid bath repeatedly so I switched to using strips of 120 grit wet and dry to sand around the pipes to be soldered, putting a couple of fins on, soldering and then repeating. It's a painfully slow process. :(

Just waiting on the ultrasonic cleaner to arrive later today. Hopefully it'll clean up nicely (without breaking any solder joints, which is a myth apparently) and mean I don't have to sand the pipes after every couple of fins. I'll try and get a video of it in action later on today. :)
 
Monkey Puzzle, what conditions are you using for the fin tip? As far as I am aware there are three cases, when the fin is very long, when the fin is adiabatic and when the fintip has the same Heat Transfer Coefficient as the fin.

You'll do yourself wonders if you were to consider this a 1 dimenional problem. I.e. The conduction is along the axis of the fin and the HTC (heat transfer coefficient) is constant.
Are you using forced conduction and fully rough turbulant flow?

I've done a fair few experiments in labs and wouldn't mind talking to you to see what kind of challanges you're overcoming and possibly input anything.


Edit: Ahh, you're using passive convection! I'd be really interested to see what heat transfer coefficient you've ended up with. You'd get a better velocity and temperature profile for forced convection.
 
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Ricochet J said:
Monkey Puzzle, what conditions are you using for the fin tip? As far as I am aware there are three cases, when the fin is very long, when the fin is adiabatic and when the fintip has the same Heat Transfer Coefficient as the fin.

You'll do yourself wonders if you were to consider this a 1 dimenional problem. I.e. The conduction is along the axis of the fin and the HTC (heat transfer coefficient) is constant.
Are you using forced conduction and fully rough turbulant flow?

I've done a fair few experiments in labs and wouldn't mind talking to you to see what kind of challanges you're overcoming and possibly input anything.
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That's really nice of you to offer - the radiator's nearly finished so I can't change the design or anything, but I don't suppose you have any experience of usinga program called EES (engineering equation solver)? It's used to accompany a book called Heat Transfer by Klein and Nellis, published by Cambridge University Press.

It has the equations used for natural convective heat transfer and the problem I've adapted (Heat transfer option at the top, chapter 6, example 6.2-3), which you plug numbers into for the dimensions of the heatsink, fin pitch (spacing) and fin width, and it calculates the results and allows you to plot them. It can be downloaded here if you fancy taking a look - the trouble I have is I can't find what equations it uses to calculate results, and so I don't know what assumptions it makes other than it treats the heatfins to be the same temperature throughout (stated in the problem sheet that loads with example 6.2-3). I don't think that is a problem for my radiator design since the pipes are spaced about 2cm apart (edge of one pipe to closest edge of the next), but by trying to adapt it for the greater area of 48 tubes transfering heat to the fins compared to a hotplate at the 2 ends in the model (by reducing the distance between the two hot endplates and increasing the width to maintain fin surface area) it gives unbelievable results and I'm not sure why. If you're able to work it out I'd be very impressed. :cool:

Edit: Ahh, you're using passive convection! I'd be really interested to see what heat transfer coefficient you've ended up with. You'd get a better velocity and temperature profile for forced convection.
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Yeah, interested to see how it does myself! It will have space to fit 18 120mm fans if I really wanted to, and though the fins are spaced 2.5fins/inch so screaming deltas probably won't gain much above quiet fans, the overall surface area of the finned part plus tubing going through the finned part where fans blow is about 37,000cm^2, so around 5x that of a TRUE, plus it's copper - might go crazy and try it out at some point in the future! :D
 
Btw, does anyone have any experience of brazing copper, or soldering copper radiator innards? I'm making a copper rectangular box so need to attach the sides by soft soldering with tin/silver/copper solder (96%Sn,3.5%Ag,0.5%Cu) if I can - I presume that galvanic corrosion won't be a problem since Copper and Tin are close to each other on the reactivity table, but if anyone thinks it will be a problem or has experience please let me know! I'm not sure the blowtorch could get anywhere near brazing temperature (~850C) but hard soldering with silver solder may well be possible (650C ish) since the propane/butane blowtorch is rated at getting copper pipe to around 650C. Alternatively, a friend has a TIG welder... but I'm not sure that is sensible and don't want him to hand me a melted lump of what was once a radiator!


I'm nearly done with making the radiator - 69/74 fins done so at the ends where the plenum/manifold will be.

I decided to go the route of having a copper rectangular box at the top and bottom for the manifold. It won't be as pretty as acrylic block, but trying to get a good seal and screws in the 5mm edge around the pipes just doesn't seem feasible, unfortunately, and I have 4 copper fins that haven't been drilled to use, so no extra cost. Plus, time is against me, and a copper manifold is quicker and easier to make: I need to finish this project before the end of the month really, as I'm moving for my job and won't have access to tools.

I'm getting a friend to mill holes in copper cylinders for the inlet, outlet, fill port and drain port this weekend hopefully, which will then be tapped and joined.
 
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FLIPPING HECK :eek:

but this has given me an idea......we could make our own CPU tower cooler, this would be excellent.....and get the finished assembly chrome plated
 
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Monkey Puzzle said:
That's really nice of you to offer - the radiator's nearly finished so I can't change the design or anything, but I don't suppose you have any experience of usinga program called EES (engineering equation solver)? It's used to accompany a book called Heat Transfer by Klein and Nellis, published by Cambridge University Press.
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Monkey, I have the program on my PC (and I've played around with it a few times) at home but wont be at home until Monday. I'll bump this thread when I get round to helping you Monday night. :)
 
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Been a while since I last looked at this!! Hope its still going well :) Hope the ultrasonic cleaner can clean it up nicely, would be the easiest way by the looks of it!

Good luck with the rest of this, seriously an impressive build!
 
Derek W said:
I have no idea what you are doing here :confused: it looks like a giant version of my cpu cooler but in copper...
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Yeah, that's sort of what it is, but cpu air-coolers use heatpipes (containing water at low pressure) whereas this is a water-cooling radiator so has water running through the pipes.

Ducky Spud said:
Been a while since I last looked at this!! Hope its still going well :) Hope the ultrasonic cleaner can clean it up nicely, would be the easiest way by the looks of it!

Good luck with the rest of this, seriously an impressive build!
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Cheers man; almost all the fins are on - just the end-fins and the rectangular plenum/manifold boxes to go on the ends plus inlet/outlet/drain plug/fill-point to be soldered on. Unfortunately my friend is waiting on a new motor for his lathe so don't have the ports back yet.

The ultrasonic cleaner didn't do that much, but tbh I don't know what cleaning solution to use - washing up liquid didn't seem to do much and I don't want to ruin the solder joints with acid.

I figured updates would just show more fins on at this stage, so not that exciting really.
 
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