Does this water pumping device use the Rankine cycle?

@Thermodynamics Forum I’m thinking it may similar to the Lenoir cycle only in the pressure/volume graph that I’m imagining is going on in this system. I know the Lenoir cycle is a gas cycle, which definitely doesn’t correspond with this. That’s why I initially thought that it must follow the Rankine cycle because there’s a phase change, but the more I think about what may be going on the less I think it must follow a Rankine cycle.

Just to touch on what you said about open and closed systems. I think this may actually be a closed system. My reasoning is this, I believe the “working fluid” in this system is ONLY the water in the very bottom of the “playpipe”, the water where the heat is applied. I think the same water boils and then re-condenses every cycle. The water above this is the pumped medium. The water that is pumped out is very cool, telling me it’s absorbing little to no heat from the heat source. Also no steam has ever come out the outlet, which also tells me there is some sort of separation between the expansion medium and the pumped medium. The final reasoning is that the amount of water in every “discharge” stroke is quite a bit less than the entire playpipe holds, so that tells me only a portion of water at the top of the playpipe is every pumped out, and being that the water is always cool then it must be that the water in the bottom always stays in the bottom. If these assumptions were correct, could we then consider this to be a closed system?

I will be honest, some of the thermodynamic processes confuse me and I don’t fully understand them, but I will take my best stab at what I believe is going on.

I believe process 1, the heating process, is isochoric. The playpipe is full of water with no air space to allow for expansion. The outlet valve has a column of water in front of it holding it closed with a certain amount of pressure. So when heat is added, expansion cannot take place, not until temperature and pressure conditions are met to overcome the outlet valve. So the water at the bottom of the pipe is heated, cannot expand, so the pressure goes up and volume stays the same.

I’ll be honest I don’t really understand the isentropic process, so I can’t say for sure if the expansion process in this system is isentropic or not. I do think however in the expansion process in this system that the PV graph would look very similar to that of a Lenoir cycle, if we are only following the small volume of water at the very bottom of the pipe that is. If we do that, then once the water finally meets conditions to boil, it will expand, our volume goes up on the graph, and while expanding the pressure would go down.

Is it possible do you think that the expansion process could be isothermal? I only say this because the heat source is never taken away, so could it be a reasonable assumption to say the working fluid is more or less held at a constant temperature in this case?

The last process I’ll admit has me stumped as to what it is. I think I’ve abandoned the idea that there is a “cooling” stage in this system. I think the reason the steam condenses back to water is simply because it used up all its energy pushing water through the outlet. As we know if you make steam do work it will lose energy, if it loses enough it will condense back to water. I believe this is the reason for the condensing stage, not some sort of cooling affect as I thought before.

As for what process the last one is, I honestly have no clue. Thermodynamics still goes a little over my head at times, but I do really enjoy learning more about it. I believe it may be isobaric though, as volume is going down and most likely the pressure would remain constant, but I could be very wrong.

Part of where the Lenoir cycle came to mind is after I read a short article where someone mapped, or at least attempted to map a PV diagram for a Putt Putt Boat, and it was mentioned how it ended up looking similar to the diagram for a Lenoir. After thinking it over I realized what I’ve made here is very similar to how a putt putt boat works, just with added valves and slightly different orientation. I’ll post it down below, let me know what you think :)

Sorry for such a long reply, but if you have any thoughts on anything I mentioned let me know, even if just to say that I am way out to lunch :)

@justincorhad Yes, I am also a little bit confused about how to draw a P-v plot for this. But in my opinion, this is an open process for sure. If you imagine this system to be sending water continuously from one place (bottom) to another place(top) this has to be an open system.

Look at it as just a pump that pumps water from the bottom to the top (if it works continuously).

The valves you mentioned are present inside a pump in the Rankine cycle too.

But the pump is just one part of 4 flow devices in the Rankine cycle.

1.Boiler

2.Turbine

3.Condenser

4.Pump

I will do some search about this kind of system if anyone has tried to make it and let you know if I find something that would be useful to you. Until then I encourage you to keep doing the experiments. Keep iterating until you find the best possible system.

Also, Keep measuring quantities like pressure, volumetric flow rate, and temperature while doing experiments.

Cheers. :)

@Thermodynamics Forum oh okay I totally understand what your saying about the pumping system being an open system. I was referring to the “working” part of the system possibly being a closed system, meaning just the bottom inch or two of water where the heat is added. I imagine 3 parts to the water as it were, the portion in the top being was is pumped in and out, the portion in the middle acting almost like a piston, and the portion in the bottom being the part that boils and condenses to accomplish the work. That’s just the way my mind works though and may have no basis in reality lol

If you find anything interesting though just mention me on here :) if I discover anything new I will post it here as well :)

@Thermodynamics Forum

The heat source is definitely intense. I think I am using it in a very inefficient way, a lot of the heat is just escaping to atmosphere. If I can come up with some sort of insulated shroud that would probably help a lot. Another thing I was thinking is exchanging the single big tube for multiple smaller tubes in an attempt to capture and utilize more of the heat applied by having more surface area being heated. If none of that shows any great improvements the only other option would be to stack multiple sections together, I mean at the end of the day this little 25mm tube is only ever going to be able to pump so much water on it’s own, regardless of any efficiency improvements I can make.

it will definitely be interesting to see what the maximum suction length could be. I built a simple Venturi pump a while back, and with that system I could not discharge the water more that 12 inches or so above the outlet, it would not work. However I put a 30 Foot suction line on it and it pumped great! Maybe this we be similar.

The experimenting part is definitely fun, the physics and thermodynamics is the part I struggle with, I feel like if I can get a better understanding of how it works that maybe I could make the setup more efficient.

@justincorhad Yes stacking the pipes and having some insulating surface would represent a boiler like structure that is used in steam power plants. But do not make it very small because that would increase frictional losses inside pipe and it will reduce pumping performance. As head loss due to friction is inversely proportional diameter of the pipe. (Check out Darcy-weisbach equation for more info. about this)

I think if you increase the height of the delivery pipe it will become more and more difficult for water to flow as the effect of the gravity will also come into the picture. And water will start boiling and start getting converting into steam because it will gain more and more heat because it will spend more time in contact with heat source at the bottom.

Keep experimenting. :)

That is better way to understand things in my opinion. Almost all the laws of nature have come from experiments. :)