A while back a was messing around in the shop, and ended up making this water pump that uses only heat to pump. The two check valves are the only moving parts. Here is a video of it working...
Here is a drawing of what it looks like inside...
Here is another drawing of what I believe it is doing in its cycle....
The system is primed with water a bled of any air that may get trapped in the system. It’s starts to pump within 30 seconds of applying heat to the bottom of the pipe.
I believe what’s going on is that a pocket of steam is formed at the bottom of the pipe. Being that there is no air or space for the steam to expand to, instead it pushes up on the water column and forces it through the outlet check valve, achieving its expansion that way. Once the steam no longer has the energy required to continue pushing the water column, the outlet valve closes, and the pocket of steam begins to cool, having lost a good portion of its energy. Asthe steam cools in begins to contract a form a partial vacuum in the bottom of the tube. This vacuum in turn opens the inlet check valve which supplies more water to fill the voided space in the unit. The cycle then continues.
I believe it has to be using the Rankine cycle, but when I try to draw out a rough and dirty PV diagram I kind of run into a bit of a wall and get nowhere.
Can anyone explain what’s going on here a little better to me? Perhaps what I think is going on is completely wrong and somebody else has a better idea that would help me understand more. Thanks for any replies!
Well unfortunately I have come to the conclusion that it is indeed the vertical height increase that increases the flow rate.
I switched out the 2 foot 1” pipe for a 2 foot 1/2” pipe, I also had to add a 1” to 1/2” reducer along with a 6 inch long 1” pipe to accommodate the heating element. This brought the total height of the leg to roughly 32”, which is approximately 7-8 inches longer than it was when I was using the 2 foot 1” diameter leg.
The result from this was about 2.3 liters per minute or so. Roughly 0.2 - 0.3 liters per minute more than I was getting with the 2 foot 1” diameter leg. This tells me that increasing the volume does not in fact increase the flow rate, only increasing the height of the leg.
This result is actually quite disappointing to me because I figured if the volumetric increase was the deciding factor than it wouldn’t be too difficult to build something of a practical size with a practical flow rate. For example it would be feasible to build the pumping chamber to be a 4 inch diameter that was 10 inches long or so, doesnt really take up a whole lot of space.
Unfortunately it would seem to me the only method method of increasing my flow rate with this setup is to make the pipe longer and longer. Its not very practical to have a pump that’s 20 feet tall in order to pump 2-3 gallons per minute.
i’m not quite giving up yet though. I would like to find out if the height increase is affecting the flow rate because of the pressure increase that goes hand in hand with that. If it is in fact that the boiling point is increasing, than maybe some sort of calving setup could accomplish the same results without the need for an absurdly long pipe.