Rocket stove pool heater.

Hi all,
I'm after some advice please. I have recently built, what I now know isn't actually a rocket stove, to tru and heat an above ground 12' round pool. The main parts (horizontal and vertical sections) are 6" x 6" hollow section and the fuel feed is 4" x 4". I have 3no 3mtr 15mm copper pipe coils running up the chimney.

Although this does a fair job of heating the water running through it, I dont seem to be getting "rocket effect" whilst burning.

Any suggestions on how I can improve this?

Many thanks

Hi Joe; Welcome to Permies!
Joe I have to tell you that if you ever get your stove up to true rocket performance you stand a good chance of a catastrophic failure.
In a standard well burning rocket, temps in the riser approach 1500 F Your water would flash to steam and bad things happen to copper pipes and bystanders.

Sorry to start out on a down note but we really stress safety around RMH's and water.
Here is a link to a super cool rmh water heater that might be a better option for you.
https://www.permaculturenews.org/2012/11/23/rocket-stove-hot-water/

Try building a rmh with clay bricks and mud. Metal only lasts so long before spauling into oblivion.
Stick with 6" dimensions throughout , with a standard J tube design.  Seal any possible air leaks with cob (mud)
Stand back as this design will rocket like you expected from your design.  

I would agree with Thomas on the safety factor. An open system is way more safer and there are many people that have built one with great results.
I suspect your getting such poor draft due to the fact that you've plugged up about 1/4 of the heat riser with the coil, adding a whole lot of drag to slow down combustion.

Hi Thomas,

Thanks for your advice. Do you think it would be safe to use this temporarily as I'm not getting "hot" temperatures until I build something else?

Gerry Parent wrote:I would agree with Thomas on the safety factor. An open system is way more safer and there are many people that have built one with great results.
I suspect your getting such poor draft due to the fact that you've plugged up about 1/4 of the heat riser with the coil, adding a whole lot of drag to slow down combustion.

Ah right, I hadn't thought that the pipe would restrict air flow. Obvious now!

It looks open enough to me to be safe; I don't see any valves or anything. If it were to reach the boiling point, the pressure should go out each tube if the pump were to fail or something. I imagine the problem has something to do with the restriction as mentioned, or the area where the fuel meets the air may not be optimal.

Hi Joe;   With care I think it will hold up until you can make changes.
Just don't get carried away trying to get a roaring fire. If you get it to hot...We call it squish boom...
The thing about water in an enclosed pipe. If it spot heats to steam  it collapses the copper pipe (this is the squish) The pipe splits allowing the steam and super hot water to explode outward(this is the Boom)
You might think that the hot water would just squirt out the pipe as Jordan suggested.  Things happen in split seconds going from a liquid to a gas. No time to push water out a pipe, its less work to blow a seam.
So please be careful ... Oh and welcome to the wonderful world of Rocket Science!

Jordan Holland wrote:It looks open enough to me to be safe; I don't see any valves or anything. If it were to reach the boiling point, the pressure should go out each tube if the pump were to fail or something. I imagine the problem has something to do with the restriction as mentioned, or the area where the fuel meets the air may not be optimal.

Thanks Jordan,

I haven't 100% got my head around the science behind all of this yet but I'm having fun finding out. Just dont want to blow myself up in the process haha

thomas rubino wrote:Hi Joe;   With care I think it will hold up until you can make changes.
Just don't get carried away trying to get a roaring fire. If you get it to hot...We call it squish boom...
The thing about water in an enclosed pipe. If it spot heats to steam  it collapses the copper pipe (this is the squish) The pipe splits allowing the steam and super hot water to explode outward(this is the Boom)
You might think that the hot water would just squirt out the pipe as Jordan suggested.  Things happen in split seconds going from a liquid to a gas. No time to push water out a pipe, its less work to blow a seam.
So please be careful ... Oh and welcome to the wonderful world of Rocket Science!

Hi Thomas,

Thank you for the welcome. It seems I have a lot to learn! I'll be giving your suggestions a try as soon as I can source material.

Joe

Kevin Vader wrote:In my opinion, as a rocket man who has been engaged in rockets for the past 8 years, I can say that some additional atomizer or candle is missing. And also there is a lack of air. Try to make cuts outside

Hi kevin, can you elaborate on the atomiser/candle please? And where do you think would be the best place for cuts?

Tia

thomas rubino wrote:Hi Joe; Welcome to Permies!
Joe I have to tell you that if you ever get your stove up to true rocket performance you stand a good chance of a catastrophic failure.
In a standard well burning rocket, temps in the riser approach 1500 F Your water would flash to steam and bad things happen to copper pipes and bystanders.

Sorry to start out on a down note but we really stress safety around RMH's and water.
Here is a link to a super cool rmh water heater that might be a better option for you.
https://www.permaculturenews.org/2012/11/23/rocket-stove-hot-water/

Try building a rmh with clay bricks and mud. Metal only lasts so long before spauling into oblivion.
Stick with 6" dimensions throughout , with a standard J tube design.  Seal any possible air leaks with cob (mud)
Stand back as this design will rocket like you expected from your design.  

Hi again Thomas, I've been thinking about this a lot again today. Can you explain to me in layman's terms how the method shown in your example would create more heat in the water than having the copper pipe in direct contact with the heat from the fire? I 100% understand the safety issues. But please forgive my ignorance as I'm an absolute newbie to this.

Many thanks in advance, Joe.

Hi Joe;  Its not that it creates more heat than your design. Your design would by all means get hotter faster.
It does so with no chance of  flashing the water to steam.

Here is a different link. http://walkerstoves.com/index.html   That is Master builder Matt walkers site.
Matt sell complete build plans for his designs.  He has just recently built a stand alone water heater, that might be to your liking.

Here is a link to Geoff Lawton building a heater like the first design I showed you https://www.youtube.com/watch?v=z-Cdx0W3Eqc
As you can see his rocket stove is very crude but works great!

There's also one at Wheaton Labs. See here for video: rocket hot water heater

Welcome to Permies Peter!