I am looking for a conceptual way of dealing with the following. I am not looking for a set of blueprints.

Consider a 5 meter x 10 cm vertical closed tube filled with a substance in the gas and liquid phases. The height is chosen to be out of range of capillary action with common materials.

The upper end is 10-30 C higher temperature than the lower end.

In normal circumstances the liquid is at the bottom, with the space above filled with the gas phase.

I am looking for simple way to move some liquid from the bottom to the top, without using moving parts, with all apparatus to be contained within the tube. Cooling part of the upper end of the tube to an intermediate temperature is acceptable.

To do it with moving parts is straightforward. The temperature difference drives a heat engine which pumps the liquid.

What physical principles can be leveraged to achieve this?


  1. A sufficiently fine grain wick can do this, but the transfer rate is low.
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    $\begingroup$ Why so many close votes? Physics isn't just a theory of everything, or even a theory restricted to spherical flow quantum mechanics. @SherwoodBotsford - What about capillary action? There are two key mechanisms by which fuel is transported from a fuel tank in a rocket to the thrusters. One involves a bladder that separates a pressurizing gas (usually helium) from the fluid to be forced to the thruster. Kludgey? Yes. The other involves passive capillary action that apparently transports fluid to the thruster by magic. Real magic? No. Google the term "propellant management device" for more info. $\endgroup$ Dec 29, 2014 at 20:54
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    $\begingroup$ AFAIK there is no engineering stack exchange. I'm not asking for a blueprint. I want to know if there is some clever physical way. I $\endgroup$ Dec 30, 2014 at 1:31
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    $\begingroup$ At least one of the close voters voted to close because he thought the question was unclear, by the way. $\endgroup$
    – DanielSank
    Dec 30, 2014 at 2:08

1 Answer 1


Summary: Yes it is possible. The easiest way uses a bubble pump -- a small heat source to heat liquid in a small tube. Rising bubbles then carry liquid with it. For this to work the pressure of the aerated column has to be less than the pressure at the bubble injection site. Thus if you injected 1 m below the surface, you would need an average density of 0.2 for it to get 5 meters above the static level in the pipe.

This can be done either by evaporating the working fluid and using an insulated pipe, or by dissolving a gas in the water where the solubility of the gas is very temperature dependent. Ammonia is a candidate gas,

Resources for other people seeking answers:

The relevant search term: anti gravity thermal siphon heat pipe

Example of a commercial, solar powered solution: http://www.bubbleactionpumps.com/about_bapl/about_bubble_action_pumps.htm

Google Books result. https://books.google.ca/books?id=yWAhBQAAQBAJ&pg=PA694&lpg=PA694&dq=heat+driven+bubble+pumps&source=bl&ots=ycFt-EebLD&sig=wbin4UOrwIoQ7_xGSY2wX2IycF8&hl=en&sa=X&ei=nAWiVP-0E5GAygS0lIGoAw&ved=0CIIBEOgBMBA#v=onepage&q=heat%20driven%20bubble%20pumps&f=false

A patent related to my question: http://www.google.com/patents/EP2270413A1?cl=en

Paper: Feasibility of periodic thermosyphons for environmentally friendly ground source cooling applications


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