Stirlingengineforum.com

I don’t know if anyone is still keeping up on this thread or will see this reply, but I did a little experimenting and managed to more than double the pumping output of this unit! Check the video out and see it.

https://youtube.com/shorts/tisahnp5ApI?feature=share

I found that:

1) you get the best pumping rate if you heat at the very BOTTOM of the Tee. Yes it will pump if you heat just about anywhere along the leg, but if you heat the very bottom it will pump more water per “stroke” as it were.

2) I rearranged the valve positions as you can see in the video. The inlet valve is above the outlet valve. I found that by doing this the bursts of water out the outlet are longer and with a bigger quantity of water each time. I can also hear a lot less pinging of the valves opening and closing. I’m thinking it might have something to do with water in the TEE configuration tries to head towards the outlet valve when it is being pushed up, but this rushing the opposite direction from the inlet valve causes a small low pressure area to build which momentarily opens the inlet valve. The current configuration definitely seems to have much better defined “intake stroke” and “exhaust stroke” as it were.

3) the longer you make the leg of the TEE, the better the flow rate will be out the outlet. This one I have to admit confuses me. I have no idea why adding length to this section would boost the flow rate so much, but it seems to be the single biggest flow booster. Perhaps it allows more heat to be held in the system so your flame isn’t trying to heat as cold of water every cycle? Honestly I’m skeptical of this being the reason, because I’ve ran this pump for 30-40 minutes non stop before, recirculating the same 1.5-2 liters of water, and after all that the water is still barely even warm to the touch. Quite frankly I’m stumped as to why this makes so much difference. You can see in the video the mess of pipes I added to the TEE leg in an attempt to lengthen it. If anyone has any idea as to why doing this would make such a big difference let me know! I am very curious to find the reason.

My best guess would be that the greater length/height increases back pressure on the second check valve so holds the valve closed longer, allowing more time for heating, more pressure build up per cycle, resulting in a longer surge when it does open.

I assume when you say "the mess of pipes I added to the TEE leg in an attempt to lengthen it" you mean the outlet pipe after the outlet check valve. Going up and over to the tank ?

Oh yes, those mess of pipes as well haha the whole thing is really a mess of pipes. Trying to change things and mess the dimensions and geometry doesn’t work so well when a guy only has a certain amount of fittings at his disposal unfortunately.

Tom, by back pressure on the valve, are you speaking of back pressure on the output side of the outlet check valve? Just so we understand each other, the extra length I was referring to was the heated section, I added another 6 inches of iron pipe or so below the outlet check valve, into which I fitted the original copper tube which is heated at the bottom.

https://ibb.co/f12Wqfk

justincorhad wrote: ↑Thu Mar 31, 2022 12:22 am ...by back pressure on the valve, are you speaking of back pressure on the output side of the outlet check valve?

That was what I was thinking.

Just so we understand each other, the extra length I was referring to was the heated section, I added another 6 inches of iron pipe or so below the outlet check valve, into which I fitted the original copper tube which is heated at the bottom.

https://ibb.co/f12Wqfk

OK, well, ...


Maybe more pipe let's it take a bigger "gulp" each cycle ?

It would be interesting if you could somehow fit a "sight glass" in that section. Or "Boiler Liquid Level Gauge", the replacement pyrex tube itself is a few dollars at most hardware stores, about the same diameter as copper tubing. Or almost any size diameter and length can be ordered online.

Or maybe a test tube?

Yeah that would be ideal for sure, actually get to visualize what’s happening in there. It’s just so strange that the flow rate increases. My thinking was that the opposite would be true, if you lengthened the tube then it has more water to try and push through the outlet, which requires more energy, which should make the “pumping out” process slower.

I could be wrong, but I believe the reason a shorter tube doesn’t work as well could be the accumulation of a “steam pocket”.

I’ve actually found that if the tube is short enough it will only pump for about 30 seconds and then stop pumping altogether. If the tube is eliminated completely and heat is simply applied to the area between the inlet and outlet valve, it will not pump any water whatsoever.

I believe what might be going on is a pocket of steam forms, which doesn’t have enough energy to open the outlet valve, especially against the weight of the water on the other side, but it still has just enough energy and buoyancy to prevent any more water from coming through the inlet valve. If water were allowed to pass through the inlet valve, even a little bit, it should trigger a condensing of the steam and further water suction, letting the cycle restart and continue on as normal.

So perhaps by lengthening the tube, the chances of forming a steam pocket near the valves diminish, this would either slow or completely stop the process. The increased water weight above the heated area must be aiding in keeping the operation steam at the bottom where we want it to stay. The increased length and water weight may also aid in the condensing stage, bringing in more water to pump out.

I guess the next step would be to find out how much length is too much, and is there a “magic length” or ratio in relation to the diameter that will give optimum performance.

Tom Booth wrote: ↑Thu Mar 31, 2022 1:31 am

justincorhad wrote: ↑Thu Mar 31, 2022 12:22 am ...by back pressure on the valve, are you speaking of back pressure on the output side of the outlet check valve?

That was what I was thinking.

Just so we understand each other, the extra length I was referring to was the heated section, I added another 6 inches of iron pipe or so below the outlet check valve, into which I fitted the original copper tube which is heated at the bottom.

https://ibb.co/f12Wqfk

OK, well, ...


Maybe more pipe let's it take a bigger "gulp" each cycle ?

It would be interesting if you could somehow fit a "sight glass" in that section. Or "Boiler Liquid Level Gauge", the replacement pyrex tube itself is a few dollars at most hardware stores, about the same diameter as copper tubing. Or almost any size diameter and length can be ordered online.

Or maybe a test tube?

tom booth what is your email address?

This looks like a similar fluidyne pump of some sort, I just came across:


https://youtu.be/gAEv0viug4U


Solar powered?

Edit: Not solar. On rewatching the video, I see there is a hair dryer blowing heat on the pipe.

Very similar setup, with a pair of check valves.

I imagine that maybe it could be solar powered.