The key word being "properly".
Heat pipes are made with many kinds of wicking structures. Sintered metal (the best and most espensive), mesh (the generic middle ground), and grooved (the cheapest). Sintered metal and mesh are pretty much orientation independent, grooved counts on a large assist from gravity.
For any particular mobo you have 3 options to figure out what kind of heat pipe it has.
1. Cut the heap pipe open.
2. Find the engineer who spec'ed it into the design and ask.
3. Operate the board right side up, measure the temperate, then operate it upside down and measure the temperature.
I know from experience (and the cost of a new case) the the Asus M2N-E has a grooved heat pipe that has distinctly different heat transfer characteristics when right side up versus upside down.