A few years ago, cooling devices started showing up on the market utilizing heat pipes for heat transfer. When reading the laymen's description (found in many product reviews at the time), I always came away with the impression that gravity was involved in transferring the condensed/cooled liquid away from the cool end, and back to the hot end. So I always wondered how effective they could be upside-down.
Well, now I'm using the Scythe Ninja in a P180, and as you can imagin, only 3 of the 12 heat pipes comes anywhere close to the proper orientation. So I tried laying the case on it's side so that all 12 pipes were facing the ceiling.....and my temps did not improve. I so looked it up on the net and found that while heat pipes "can" use gravity, I don't believe our consumer level products need it, they use capillary action instead.
In the case of vertically-oriented heat pipes the fluid may be moved by the force of gravity. In the case of heat pipes containing wicks, the fluid is returned by capillary action
So, I saw someone else basing a comment on the same assumption, and it prompted me to post this thread. Now you know.