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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.
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]
Loop heat pipes
https://en.wikipedi...wiki/Loop_heat_pipe
work exactly as was described, but without a pump! [justin_case, Oct 21 2021]
Swept Boundary Layer Heatsink
Swept_20Boundary_20Layer_20Heatsink
[bs0u0155, Oct 22 2021]
[link]
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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. |
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Strange this idea went completely un-annoed for ten years. |
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[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. |
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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. |
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piezoelements are 1/10 of 1 cent at alibaba... |
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If we're in the business of annotating old ideas... |
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I get the idea, the biggest problem with heat pipes is the
liquid return. Normally, they use a sintered porous
structure and rely on capillary/wicking type movement.
This doesn't scale well and isn't fast. |
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Pumping liquids around is the standard solution to move
thermal energy around, so an obvious choice. But, you're
necessarily dealing with a liquid that's very nearly, or very
actually boiling. This is a problem. In this situation, any
type of pump will behave horribly. For example, a
centrifugal vane type pump will have the liquid boiling in
the low pressure areas on the back side of the blades, you'll
have endless gas-void/cavitation/priming problems. |
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If you want to move heat downhill, and you're OK with
moving parts, just use a pressurized water cooling loop like
a car/house. |
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//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.// |
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A sound (get it?) theory that would do exactly as you say
and improve the efficiency of the liquid/air heat exchanger
component of fridges/AC units. The problem, as usual,
comes from the inconvenient nature of the real world.
Aluminum, and it's alloys do not behave like steel for
example. They undergo "work hardening", or another way of
putting it, they have no fatigue limit. You can't make a
spring out of it, well, you can, but it only works once,
which is a crap spring. So if you subject aluminum to
repeated deformation it becomes progressively brittle and
then fails. |
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I have a practical demonstration of this, I occasionally
make fluorescent liposomes, essentially a fluorescent dye
in a lipid sphere suspended in aqueous solution. To make
them involves a lot of vibration/shaking over 12-24hrs. To
protect the fluorescent dye from light exposure I wrap the
tubes in aluminum foil, and shake the tubes at ~60Hz. After
24hrs of this, the foil is practically dust. The same would
happen to piezo-wobbled radiator fins. |
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I had an idea a while back for solving boundary layer heat
problems <link> |
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^Non light transmissable laboratory tubes and flasks is not a product? Must be. |
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CPU heatsinks routinely are hollow copper tubes with
refrigerant similar to what you describe. |
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//Non light transmissable laboratory tubes and flasks is not a
product?// |
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I'm sure, but mostly tubes are clear, and we have lots of them.
We also have tape and foil, and we don't have to navigate the
tortured bureaucracy of buying something different. That can
take weeks. |
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[bs0u0155]: duct tape solves everything (as long as a duct-
taped test tube fits in the shaker...). |
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The foil thing isn't so much a problem as a curiosity. Getting
duct tape off a tube so you can have a look might be tough.
Then, any left over adhesive would likely gum up the slots in
eh centrifuge and make me deeply unpopular. |
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