Streacom DB4 Water Build (now flat heatpipe)

[aquelito]

Minimum bending radius for 40 mm pipes is 5 mm. Seems the case here.

 

[BaK]

Nice update, thanx for the new pics!

According to the Amec's Application Notes @aquelito posted earlier:
"Working Progress
4. And working fluids return to the evaporator section in the liquid phase by the capillary pressure or gravitational force."
So I guess it is indeed better to add gravity to capillarity, but should work with capillarity only.

Minimum bending radius for 40 mm pipes is 5 mm. Seems the case here.

I think the flat heatpipes used are of 50mm width / 2.5mm thickness. Can you confirm this @StevenG?
If so, the minimum bending radius is 6mm, which the longest CPU pipes seems anyway to have (distance between the 2 sides of the U looks > 12mm).

Stacking 2 pipes together was working well with the GPU, strange it not the same with the CPU. Maybe a contact problem somewhere as @msystems mentionned it?

There are some 4mm thick flat heatpipes available on ebay.
Do you guys think they can spread heat faster as well as handling more heat/power than thinner ones?

 

[StevenG]

Wow stunning bending job !! Did you do it by hand ?
Those coolpipes are easy to bend but do not forgive any mistakes : almost impossible to bend again without breaking them.

Regarding your CPU temps, I see two possible issues :

1. From my experience, superposing two coolpipes does not work. Only the pipe in direct contact with the CPU will work.
2. From Amec recommandations, the coolpipes work much better vertically : the radiator stays above the heat source so that the condensated liquid can go back to the heat source quicker, thanks to gravity.

I think one pipe is enough for the CPU ; what you could do is try to "link" two rads with one pipe

Last week I tried to cool an i7 7700 with my HFX mCubed, made around two rads measuring 220 x 75 x 40.
I'm using a 50 x 50 x 5 mm piece of polished copper between the CPU and the 250 mm pipe.
Around 50 mm (20 mm on the left, 30 mm on the right) of the pipe is on contact with both rads.

Idle temp stabilized around 35° (ambiant temp around 20°).
After 20 min of Prime95, the CPU reached a temprature of 75°C, open case.

Both rads were very hot to touch and did saturate very quickly ; I did not try to test it any longer but I guess I would have reached some pretty toasty temps.

Conclusion : rad surface matters a lot, as well as respecting a vertical setup.
Surface contact between the pipe and the rad did not matter that much, as only 1/5 of the pipe length was enough to saturate the radiators.

Thanks for your indepth reply i completely agree with the vertical pipes unfortunately this setup would be near impossible to achieve with the DB4. I'm going to take it all apart again and check contact is being made correctly. As per the stacked design its not 100% i agree but does work to a degree I've proved it with the GPU both sides get hot one hotter than the other but still notice heat transfer. i have another 450mm heat pipe so may try less bends and just link two panels together see what happens


yes bent them by hand using a few things i found in my garage namely a vice and a 20mm pipe, it helps being an electrician i bend conduit etc so have the hand skill. i did mess up on the long pipe initially but managed to save it.

 

[StevenG]

Wow those CPU heat pipes are crazy. It is true that they are more effective vertically, but I think there is a problem with the thermal transfer. I hope it is not the bend radius. Hard to say.


I am suspicious of the contact with the CPU. The heat pipe looks like it is not completely flat due to the tiny ridges. Is it?

And also, any chance the CPU retaining socket is interfering with the contact?

Copper shim installed so should be good contact with the CPU ? unless its not flat although all bolts are tightened the same number of turns so it should be ! a rebuild is in order i think. as neat as they look i think the 180 degree bend is killing the pipe there was no other way i could achieve it really, i may try a 450mm pipe on its own and just link both side panels. The bend radius should be ok i bent it around a 20mm pipe to ensure a good radius.

 

[StevenG]

Nice update, thanx for the new pics!

According to the Amec's Application Notes @aquelito posted earlier:
"Working Progress
4. And working fluids return to the evaporator section in the liquid phase by the capillary pressure or gravitational force."
So I guess it is indeed better to add gravity to capillarity, but should work with capillarity only.


I think the flat heatpipes used are of 50mm width / 2.5mm thickness. Can you confirm this @StevenG?
If so, the minimum bending radius is 6mm, which the longest CPU pipes seems anyway to have (distance between the 2 sides of the U looks > 12mm).

Stacking 2 pipes together was working well with the GPU, strange it not the same with the CPU. Maybe a contact problem somewhere as @msystems mentionned it?

There are some 4mm thick flat heatpipes available on ebay.
Do you guys think they can spread heat faster as well as handling more heat/power than thinner ones?

Yep the Amec spec says they should take 70w each in horizontal position they are indeed 50mm * 2.5MM the distance between the u bend is 20mm yep i think we agree on the contact problem i will go for a rebuilt, its far from easy unfortunately the sides don't ant to come off with the sheer level of paste its pretty well glued haha! i may try and rebuild on the weekend sorry gents i know its nice to see timely updates i just get buried with work

 

[StevenG]

Ok did a quick rebuild, there contact issues between the case and 2nd heatpipe other than that it was fine, I applied extra paste where it looked thin in places however this has made no difference. I think the bend radius is too steep for the pipes despite still being within Amecs specs so a redesign is in order. I want to redo the GPU anyway even though that’s the one that works