Dave,
    Thanks for putting that in, I'd thought they were copper rods rather than tubing,  I went to Wiki for more detail and found they use a solution that will boil, turn to a vapor,  the vapor travels to the cooler section, where it condenses giving up all the heat it had accumulated.  Some use gravity and some use a wick to return the liquid.  So we do have a form of circulation for transferring the heat.  Now I am thinking the heat pipes should be mounted vertically for maximum efficiency which is not the case when attached to the cpu wicking helps but having max efficiency is better.
Carl2

Your research seems to be more complete than mine, Carl. I was aware of the internal wicking, but didn't know that the fluid acthally made a phase change. This must be a newer method than what I had learned about when I last looked at the process. Good to know, and makes much more sense from a physics point of view.

I've used the heatpipe coolers on a few builds I did, In fact I have a couple of them here but they are for older socket motherboards. They basically work the same as a fridge if I recall correctly and use Freon gas.  The same technology is now on most mid to high end graphics card coolers too.

There is no real problem with mounting them vertically of horizontally, either way they work well. 

Carl2
Here is a bit of information that you might find useful when considering a CPU cooler.

CPU's tend to have a maximum power rating that is displayed in the specifications as TDP, the 5820K is rated at 140 W maximum TDP.

Heatsinks and coolers also have the same rating these days, example "max. TDP 160W". What you should do to make sure the heatsink is good enough for the job is to also make sure that it's TDP rating is higher than the CPU TDP rating.

On the page we were looking at there are 2 coolers that will be fine for the 5820K, the freezer i30 and the i30 CO, both are rated at TDP 160W.

http://www.arctic.ac/uk_en/products/cooling/cpu.html?cpu_socket_intel=91