For clarity, this is the section I’ve found that by increasing it’s length the pumping rate is increased as well, so long as it is still heated from the bottom. This is the part that confuses me, I have yet to think of a reason why this might be.
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Well it’s been a while since the last post/update. I’ve made a few changes that have definitely helped.
The first thing I decided to do simply for experimental purposes was to install a thread in 1500w electric heating element in the bottom pipe. No my plan is not to make this an electric system, this is just for use while I experiment. Now whenever I make a change in the geometry of the system I know that my heating source is consistent, and therefore any increase or decrease in system performance must be directly due to whatever other changes I have made.
In order to accompany the thread in heating element I had to change the lower pipe from a 1/2” diameter tube to a 1” diameter tube. The first one I tried was a 2 foot long 1” pipe. This gave me a hair over 2 liters per minute pumping rate.
This was probably 0.75 liters or so more per minute than I had pumped with any other setup. Part of me thinks it’s because the electric heater is doing a much more efficient job at heating the water in the bottom than I was doing previously with my torch. Part of me however also thinks it may have to do with the increase in volume between the check valves, changing from a 1/2” tube to a 1” tube would give me almost 4x the volume given the same length.
My next attempt I again switched the 2 foot tube for an 8 foot tube of the same diameter. The result was an increase to just a smidge over 3 liters per minute. The heating element was the same one used previously. I know I said 2 liters per minute in the video, however after the video was taken a did several more flow rate tests that all resulted at or slightly above the 3 liter per minute mark, so I’m guessing the first run may have had some air trapped in the system.
The way I measure the flow rate is set a timer for one minute, turn the outlet to pump into a seperate container, while it pumps I have to be filling the reservoir continuously otherwise it will run empty. After the minute is up I shut the outlet valve off, and from there I dump the water collected in the container into several 1 liter bottles to get my result.
I still don’t understand why increasing the tube length between the check valves increases my flow rate, my question right now is this…
“Is it the increase in vertical height that subsequently increases my flow rate? Or is it the increase in volume associated with the longer pipe that increases the flow rate?”
Perhaps it’s the actual increase in height that makes the flow rate go up, with an increase in water height comes an increase in pressure at the bottom of the pipe. Increasing the pressure also raises the boiling point, perhaps that is what is going on.
Perhaps it’s the volume increase that increases the flow rate. As you can see, with the longer pipe, there is a much longer lasting outlet stroke, more volume coming out before the intake stroke begins again.
The other thing I have noticed is that the unit actually gives 3-4 outlet strokes before the inlet valve opens and allows more water to be sucked back in. This tells me that there must be 3-4 slightly pressurized oscillations of the water column within the pipe before the low pressure area is created to open the inlet valve.
More experiments to follow, hopefully I can solve the mystery of volume vs height.
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