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cob oven hot water design

 
Posts: 5
Location: Ryde, Australia
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hi
im looking for some plans for a hot water heater i had in a rental house once please

it was a beer keg on its side with many pipes going through it( like a steam train)
at the front was a steel  burning section, it was  triangular being wider at the top and the point at the bottom,
all of this was housed in a large cob

if anyone could help me i would realy appreciate your help
thanks
 
pollinator
Posts: 341
Location: Penticton, Canada
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building woodworking rocket stoves
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G'day Robin and welcome to the Rocket stove forums! The best I can come up with for you is Geoff Lawton's rocket stove hot water heater. Hope this helps  
How to Build a Rocket Stove Mass Water Heater, with Geoff Lawton
 
gardener
Posts: 2213
Location: latitude 47 N.W. montana zone 6A
275
cat pig rocket stoves
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Hi Robin;    I searched this morning for the very post that Gerry had at the tip of his finger the whole time... that Gerry always on the ball!
I believe this is a fool proof way for you to safely make hot water.

Your bear keg water heater sounds like it is based on a modern conventional boiler.  With the cross pipes over the fire, in the event of a sudden rupture the steam/water would douse the flames.  Hopefully before rupturing the keg.

 
robin miller
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Location: Ryde, Australia
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Thanks Gerry and Thomas.
The design I'm interested in has the fire going though the pipes.
So it's the pipes that get exposed to the fire.
Basically the fire passes through the water.  Not water pipes in the flame.
 
pollinator
Posts: 318
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food preservation cooking homestead
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robin miller wrote:Thanks Gerry and Thomas.
The design I'm interested in has the fire going though the pipes.
So it's the pipes that get exposed to the fire.
Basically the fire passes through the water.  Not water pipes in the flame.




There are those who use Old natural gas heaters up thru the center.     Often though the center is very narrow and takes time to heat it up.

I considered the idea of taking a 7 inch 1/2 inch pipe  and having it welded into a old tank and using that as a chimney.

As it has been said before,   " BOOM SQUISH"     be careful when you heat water as steam burns / death really dim a permie's perspective.
 
Mart Hale
pollinator
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food preservation cooking homestead
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robin miller
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Location: Ryde, Australia
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Thanks mart.
This design has no build up of pressure as it works similar to low pressure slow combustion stoves. A 1/2 inch pipe goes up in the air as the pressure release.

The keg basically has about 10-15 pipes running through it. The fore passes through the pipes.
Around the pipes is water.
So no pressure build up.

I have a rough idea of the design .
I'm just trying to find some plans to save me doing it twice. Or ten times. Lol
Thanks
 
robin miller
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Location: Ryde, Australia
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this is sorta what im looking for,
excuse me for the rough pics
end-view.png
[Thumbnail for end-view.png]
sideview.png
[Thumbnail for sideview.png]
 
gardener
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Location: Upstate NY, zone 5
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You wouldn't want to build a heater the way you have shown - as is, the fire would hit the water heat exchanger before it finished burning, and deposit tons of creosote right in the exchanger. Pollution, inefficiency, and danger. You would want the fire to do all its burning in a hot, insulated chamber, then the hot gases would go through the exchanger.
 
pollinator
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Glenn's right. You need to have a very hot, highly insulated firebox/riser to burn the wood cleanly first and then target the heat generated towards your heat exchanger.

Any cooling of the combustion area will result in a dirty burn that will smoke like crazy and deposit tar and creosote.
 
Posts: 280
Location: Philippines
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You are referring to a "shell and tube heat exchanger" It could work but cover on the exit of fire is removable so that you can clean it up with tube brush. Its not difficult to do. One thing you should know is to put the water inlet opposite the fire inlet, more efficient and prevent  thermal shock. Its actually more efficient when fire touches the tubes because heat transfer is directly proportional to differential temperature. Then try to put higher stack for more flue velocity. Also heat transfer is directly proportional to fluid velocity and the amount of surface area. More smaller tube better than few big ones. Although more difficult to construct also. If you use hard water there would be scale build up on the water side. You can use cleaning soda to remove it. But you will need a bottom drain to extricate the lose scales. Just fill the shell with saturated cleaning soda solution boil the water and soak for at least twelve hours longer better. scales should come off the tubes. Or better else use rain water for less scale buildup. Dont fire the HE without first filling it with water. As mentioned above you'll need a clean burn to save for cleaning sessions.



 
robin miller
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Location: Ryde, Australia
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Thanks for the input.

The build-up of soot and scale is an issue.

This design DOES work.
Ive used it many times.

For the scale I'll need to seriously think about that one as it's bore water.

The pipes that carry the flame I used to clean with a metal pipe cleaner thing.

But down the road it may have had issues with the soott and creasote at the flue end.
So I'm thinking that an access panel would be needed.

As for the clean burn issue.
The exhaust gases were very clean.
Whoever built it got the dimensions correct.

It would use about a bucket of small sticks to fill a bath with hot water.

I'm starting to wonder if it's the only one in existence as I can't find any pics or info on the net. Yet.

Thanks
 
julian Gerona
Posts: 280
Location: Philippines
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robin miller wrote:Thanks for the input.

The build-up of soot and scale is an issue.

This design DOES work.
Ive used it many times.

For the scale I'll need to seriously think about that one as it's bore water.

The pipes that carry the flame I used to clean with a metal pipe cleaner thing.

But down the road it may have had issues with the soott and creasote at the flue end.
So I'm thinking that an access panel would be needed.

As for the clean burn issue.
The exhaust gases were very clean.
Whoever built it got the dimensions correct.

It would use about a bucket of small sticks to fill a bath with hot water.

I'm starting to wonder if it's the only one in existence as I can't find any pics or info on the net. Yet.

Thanks




The past week I was actually thinking of making almost exactly the same as this to heat our baby swimming pool. In my case I was thinking that the end cover opposite the fire feed end, should be fasten by bolts. Thus removing the cover gives you access to the inside of tubes. Just because you dont see smoke coming out the stack means its burning very clean. The inside of the tubes should be the proof of clean burn.
Also I will go for a longer profile and smaller diameter for efficiency. The baffles is to make the water have a longer travel and also holds the tubes to prevent it from dancing. As for a cleaner burn I have publish a proposal, Actually its an entirely new concept far as I know I invented it. You can try it for fun https://permies.com/t/107056/Steam-Injected-Wood-Burner
 
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