Half a croissant, on a plate, with a sign in front of it saying '50c'
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Active Heat Pipe

Move heat downhill
  [vote for,

Firstly, I'll mention that I've used this idea in the two most recent ideas I've posted, and thought that it merit's it's own page.

The idea is relatively simple, but I haven't found anything very much like it on google.

There are two heat exchangers (HXs), one at at some high location, and other at a low location.

At the bottom of the lower HX is a liquid sensor, and a pump (probably hermetically sealed, like the pump in an air conditioner system). Whenever liquid is sensed, the pump turns on.

The top of the upper HX is connected via a pipe to the top of the lower HX, and allows gas to flow from the upper HX to the lower HX.

The whole system is vacuum purged, and filled with a refrigerant. The amount of refrigerant is enough so that the pump, the pipe from the pump to the upper HX, and the upper HX, can all be filled with liquid refrigerant, with the rest of the system filled with gaseous refrigerant.

When heat is added to the upper HX, the refrigerant boils there, raises the pressure in the system, and causes some of the gaseous refrigerant in the lower HX to condense, giving off heat. The condensate moves (by gravity) down to bottom of the lower HX, triggers the liquid sensor, and activates the pump. The pump of course moves the liquid back to the upper HX.

As with a regular heat pipe, heat is moved by evaporation and condensation. The only real difference is that condensate is moved from one end to the other by a pump. The pump is only working against gravity, and is not doing any compression, so little energy is needed to run it.

Efficiency can be maximized by selecting a refrigerant such that the latent heat of vaporization, divided by the difference in density between liquid and gaseous refrigerant, is maximized.

Water has a fairly high latent heat of vaporization, so it's probably best for this application.

goldbb, Oct 01 2009

My first idea with a powered heat pipe Solar_20Steam_20Cooling
[goldbb, Oct 01 2009]

My second idea with a powered heat pipe Solar_2fAntisolar_20Heating_2fcooling
[goldbb, Oct 01 2009]


       My understanding is that regular passive heatpipes generally work just fine for moving heat downward, as long as they're built with wicking structures inside to convey the liquid back up by capillary action.
notexactly, Oct 04 2019

       Strange this idea went completely un-annoed for ten years.   

       [notexactly]'s annotation makes me wonder if a piezobuzzer attached to a heat pipe would increase its capacity with the continued appearance of no moving parts.   

       Another use for a piezovibrator is to vibrate the external heat shedding coils at a household fridge; they could see if microwiggles disrupt boundary layers and cause better cooling. This could also benefit air conditioners and heat pumps.   

       piezoelements are 1/10 of 1 cent at alibaba...
beanangel, May 10 2021


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