Is the orientation of a heat sink with heat pipes important for cooling efficiency?

Question

I have a heatsink designed for use in a PC. It has 6 heat pipes that go up to the fins from the base which would sit on the processor.

I want to use it for cooling a Transistor. Can I use it upside down, or do the heat pipes rely on some convection to work correctly and therefore need to be a certain way up?

Basically I want the heat source on to and to have all the cooling pipes and fins below. I know this is fine for a solid sink, but I'm not sure about the heat pipes.

Answer 1

The "heat pipes" I have seen several years ago were position sensitive because the liquid "return" was pitched even though there was some wicking involved too. These were large industrial units.

With your heat source on top, the condensed liquid will have to travel up to be evaporated. I just do not believe that will happen because the evaporation vapor pressure will be higher on top too.

As I said, it has been a while. I hope to see the other answers too.