Passive 'ventilated attic' cooling using an old fashioned heat pipe

[MattM]

I had this crazy notion tonight on how to passively pump heat out of hot attics.  So I created a crude drawing to demonstrate the idea.  And technically, because its a heat pipe this is technically a steam-powered thermal transfer engine.  My drawing exaggerates the necessary slope for such a contraption, as even a quarter inch of fall every ten feet would suffice.  Generally in heat pipes are wick material but this idea replaces the wicking with gravity.  So the length of the heat pipe in the attic runs just under the ridge in the internal side of the attic of a ventilated attic.  The pipe would protrude out a gable end preferably for simplicity sake, but it could just as well be integrated into a hip ridge or other area, so long as that there is a proper transfer to the external side of the roof.  On the outside there would be a black aluminum pipe to wrap the heat pipe around, so that the heat is transferred to the black pipe.  And a white sleeve would go around the black sleeve, to create a temperature gradient.  The white sleeve does not need to be metal because it needs to be cooler than the black sleeve.  The difference in temperature should draw air from the bottom side of the white sleeve, passively cooling the high end of the heat pipe.  A gentle breeze would add to the cooling power.  Solar radiation would not likely play any role.  Fluid in the heat pipe will then condensate and gravity will drop it back down to the hot end.  The heat in the attic will be parasitically drawn to the external heat exchanger, cooling the attic.  I'm thinking with simple SharkBite connectors it would be easy to install a T-bar handle to trap the fluid in the low end during the cooler months.  Heck, most of the thing could be pex tubing for all it matters.  (On opposing gables have a heat pipe on each end to double up the exchange.)  The heat exchanger would best be copper or aluminum tubing.  And the hot end should at least have ten feet or so of copper pipe.

Is this a crazy simple idea, or just crazy stupid?

[MattM]

Kind of neat that simple sharkbite endcaps on a ten foot stick of pex and some acetone seem to work to some degree.  But I'm worried about how warm it has to get using a heat gun to start boiling.  Maybe methanol would be safer and its supposed to operate from a lower temperature starting point.  I don't have any of that chlorinated gas-impearmable stuff to try.  And no idea how long pex would hold up. Would hate to be leaking chemicals into an attic.  Instead of heating the pipe I wonder if a vaccuum can be 'charged' into the pipe and trapped into the system with a t-handle valve.

The prospects of carrying heat 500x faster from the roof to the outdoors seems like an untapped potential.  I guess I also need to think how to dump the heat once it would touch exterior air.  Pex apparently has little UV resistance and doesn't coil worth crap.  If I was going to have copper transitions I'd need to invest in non-sharkbite fitting.  But I would prefer to keep it pex as much as possible for cost and simplicity sake.  I'm thinking pex can coil rafter to rafter easy enough I could get away from many joints.  It however would be tough to do a pre-charge of the system unless a vaccuum worked.  And then it has to maintain.  Don't want something that has to be regularly recharged.