Half a croissant, on a plate, with a sign in front of it saying '50c'
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Osmotic pressure heat engine

Osmotic pressure based heat powered pump for pressurising liquid
 
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Osmotic pressure increases at higher temperatures, so this device has a pipe of salt water or other mixture with one end being heated and the other end cooled. Osmotic pressure pulls in water at the hot end, which had pure water outside, with more than enough pressure left over to push it out the cold end into another volume of pure water. The pipe loops back to allow the more concentrated mixture to flow back to the hot end.

Since I'm not planning a perpetual motion machine, I expect the process cools the hot side, requiring a heat source to maintain the temperature, and similarly needing a heat sink at the cold side.

Circulation: the cold concentrated brine/syrup needs to circulate back to the warm end. This can be done either with a low power normal pump or with gravity.

To do it with gravity, the pipe is made into a loop, the hot side membrane is just after the bottom, so the liquid becomes warm and dilute and light after that, so it rises to the top, and the cold side membrane is just after the top, so the liquid becomes cold and concentrated and dense after that and sinks top the bottom.

To reduce unnecessary heat dissipation, there's a counterflow heat exchanger. This can be left out if you don't care about efficiency. In one direction, the hot less concentrated brine/syrup moves to the cold end, and cools down. In the other direction, the cold more concentrated brine/syrup travels to the hot end, and warms up, and the unpressurised input water also travels to the hot end, and warms up, before getting sucked through the membrane into the brine/syrup.

The system can be run in reverse to use as a hydraulic powered heat pump. Push water in the cold end, cooling that end further, and let it flow out the hot end, heating that end further.

The system can be used to power a hydraulic vehicle, or to pressurised your home plumbing, or a town water supply, or a camping shower, or for circulating water in a solar hot water system.

If using gravity for circulation it should be basically silent.

When run in reverse, it may be possible to make a quieter air conditioner. You could also use it with a powered pump to heat water instead of a home hot water heater or a kettle.

caspian, Oct 09 2016

Clusius-Dickel separation tube https://books.googl...sius-Dickel&f=false
Useful [8th of 7, Oct 09 2016]

Illustration http://karma.neocit...ure-heat-engine.png
Here's an illustration without the heat exchanger [caspian, Oct 10 2016]

[link]






       Similar to a Clusius tube.   

       <link>
8th of 7, Oct 09 2016
  

       /Osmotic pressure pulls in water at the hot end, which had pure water outside/   

       Other parts of the idea make me think the hot end has brine which you are trying to desalinate. I am not sure why one would have such a pipe with pure water on both ends. Maybe an art project?
bungston, Oct 09 2016
  

       [8th] yes it is kind of similar. Could use an electric heating element.   

       [bungston] I forgot to say where the membranes are. There are two membranes, one at the hot end, one at the cold end, allowing water to flow into or out of the loop of pipe. The brine is inside the loop of pipe, the pure water is on the outside.   

       The purpose is to pump the water, i.e. transform the unpressurised pure water coming in to pressurised pure water going out. Osmosis is just the internal mechanism.
caspian, Oct 10 2016
  

       I've added an illustration, though it doesn't indicate the pressure, which should be higher at the output [edit] it now indicates pressure
caspian, Oct 10 2016
  
      
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