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At a local workshop we have a portable and old heating device where the heat generator's housing reaches around 180°C during operation. The original external aluminum radiator with a fan attached to it have small dissipation capabilities. The integrated heat protection often trips that sometimes breaks our work waiting it to cool down a bit. We decided to give it a go and attach two old CPU tower-type coolers, each has 4 heat pipes to it.

The idea is to remove their pipes from their bases, straighten the pipes (slowly) and cross them so the fins are in the four directions and in one plane.

The problem is now clear; Which one is better for cross-connecting the pipes, soldering or brazing, Which will hold against the 180°C?

Note: That this will be a pure spare-time project before the better device arrives

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1000Gbps
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  • It is unclear what it is exactly you are doing or trying to achieve. – Alaska Man Jan 13 '21 at 21:19
  • To connect crosswise the copper pipes of two CPU coolers and the connection to hold against a high temperature – 1000Gbps Jan 13 '21 at 21:21
  • WHY, **What are trying to achieve, what is the end goal?.** What does crosswise mean? What are the CPU fans cooling? More info is needed. – Alaska Man Jan 13 '21 at 21:24
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    cpu cooler pipes contain refrigerant of some kind ... be very careful when bending them – jsotola Jan 13 '21 at 21:27
  • Copper pipes for plumbing and heating, including boilers at high temps, are sweated with solder. – Alaska Man Jan 13 '21 at 21:27
  • The difference between soldering and brazing is primarily the temperature the filler metal melts at which is basically irrelevant to your situation. – whatsisname Jan 13 '21 at 21:29
  • @AlaskaMan To improve the cooling of the device before the new arrives. The original cooling is not efficient and we decided to use a cpu coolers. Added a small scheme for more clarity – 1000Gbps Jan 13 '21 at 21:31
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    This is more industrial fabrication than home improvement, but brazing is considered the more robust approach. It's required for gas piping, for example. – isherwood Jan 13 '21 at 21:33
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    Also, a quick search reveals that plumbing solder melts at about 182 C, so that seems relevant, @whatsisname. :) – isherwood Jan 13 '21 at 21:35
  • Should we use copper pad between both pipe groups and another one between pipes and the heat source for better conductivity? – 1000Gbps Jan 13 '21 at 21:39
  • What is the heat source devise, make and model, what is its primary function? Perhaps if we understood what it is then we could provide an informed answer or alternative. – Alaska Man Jan 13 '21 at 21:43
  • It's a very old (and rough) hand made hot air station (weird) for wood burning design. The guy who created it made a constant 180°C (too much) heat source and probably added the heat protection if someone forgets to turn it off. The owner of the shop said it will be a shame to throw it because it has a sentimental value ... – 1000Gbps Jan 13 '21 at 21:56
  • Perhaps something to prevent if from reaching 180°C in the first place instead of trying to cool it after it reaches 180°C – Alaska Man Jan 13 '21 at 22:04
  • The owner of the shop usually leaves it on so it is 'ready for work after i'm back 15mins later' ... Can't picture it right now, but will try explain what it looks like - a small metal case with a heater from a hot air gun set to 180°C + the blower different gun and heat protection attached to the housing ... and on this housing the creator put an old alu heatsink with a fan – 1000Gbps Jan 13 '21 at 22:13

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CPU heat pipes are filled with low-boiling chemicals, such as water or alcohol. At 180°, likely above the critical temperature of the coolant, there would only be supercritical fluid in the tubes, and the heat pipes would no longer function. Further, they might burst, whether soldered or brazed.

Why not just add an auxiliary fan -- perhaps a squirrel-cage (centrifugal) blower, if there is high back-pressure? These blowers produce high airflow in limited area, and are used for cooling devices dissipating tens of thousands of Watts, such as transmitting valves (AKA "tubes", to the US).

DrMoishe Pippik
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  • Sadly there is not enough vertical room (max 6cm) in the housing for anything except more fins – 1000Gbps Jan 13 '21 at 21:45
  • And *outside* the housing? Surely a blower can be added before or after the heater. – DrMoishe Pippik Jan 13 '21 at 21:48
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    It has a blower from hot air gun :D This is a hand made hot air station for wood burning from spare parts and the idiot created it was close to the owner. So that owner wants this abomination to work longer without shutting down and still be the same size and same level of noise. We already offered him to buy a better station but he is on the sentimental wave ... no comment :) – 1000Gbps Jan 13 '21 at 22:06
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For strength and durability Brazing ,hands down, is the better choice. Copper brazing rods have a hire melting point than the tin solder used for plumbing. I believe the copper rods need something like 1850 F melting point.

Your problem may be that even though the CPU heat pipes are copper they are most likely very thin so if you apply 1800+ degrees of heat it will surely disintegrate.

Consider that by mechanically attaching the two metals with a copper wire will yield similar results.

ojait
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