Soldering or brazing copper pipes

Question

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

Answer 1

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).

Answer 2

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.