Tinkering with small cabin heat source...

[TimC]

This is a crazy idea but I just have to tinker.

I follow Slim Potatohead's adventures and I'm impressed with his homemade pellet stove for his camper. I don't have much in metal working skills so I'm pursuing an approach using an alcohol stove. Ideally the stove will operate outside of the cabin and somehow a water line will pass through a heat exchanger and via thermal expansion will rise and enter the cabin where another heat exchanger, maybe with a small case fan will capture the heat from the water and return to the stove and reheat.

So far I'm in the initial stages of building the stove. I have a ways to go. The prototype stove is only a 10 oz jar. I hope to fire it up in the next few days and see what kind of burn time I'll get. I've done the beer can alcohol stove before and know that it gets only about 15 minutes per oz of alcohol. They are not known for efficiency and a lot of the fuel in them is used up priming and warming the stove. Maybe ten oz will get me several hours?

I'm thinking the water line transfering the heat from stove to cabin will be a closed loop. At the stove that line will run through a bath of hot water and not be exposed directly to the flame. I would use an expansion chamber on the closed loop. Maybe a pressure relief valve of some sort as well.

While waiting for the stove adhesive to set I'm trying to come up with a wick that I can use to drive the fuel into the copper tubing. Not sure what I'll use there but I've seen people use bamboo skewers so I'll give that a go.

Stay tuned...

[troubleScottie]

There is a larger scale youtube. No idea how to get the heat into the TD -- maybe the pipe could meet a duct opening on the outside of the TD.

https://www.youtube.com/watch?v=QeHGDr81XwM

[Shadow Catcher]

I have played around with the idea of an external boiler set up but since we have a water heater which supplies the hot water I did not go further. It might however give some ideas. automotive heater core, 12V solar hot water pump 120MM computer case fan. Danger of "boiler explosion" etc.

[TimC]

[quote="troubleScottie"]There is a larger scale youtube. No idea how to get the heat into the TD -- maybe the pipe could meet a duct opening on the outside of the TD.

Those clever Finns! I love the ingenuity!

[TimC]

I have played around with the idea of an external boiler set up but since we have a water heater which supplies the hot water I did not go further. It might however give some ideas. automotive heater core, 12V solar hot water pump 120MM computer case fan. Danger of "boiler explosion" etc.

In my imagination I pictured something just like that interior exchanger with blower. Very nice. Did you use silicone tubing? I'm thinking a SharkBite type fitting inside a port somewhere on the outside of the cabin.

What do ya mean "boiler Explosion"? Naw, that couldn't happen could it?

Maybe I'll have to consider the Finn's idea of using hot, fresh air instead of water. I can visualize a simple pipe which travels near a flame and heats fresh air from the far side of the flame and into the cabin. It might be easy to dial down the flow of air inside the cabin with some type of valve. With no real closed system maybe fresh air would not create explosive pressure. Hmmm? I wonder if Cosmo has some ideas!

Tim

[Shadow Catcher]

The hose is Nylobraid plenty of temperature range for the heat of the water from the water heater. The quick disconnects seal so that water does not leak out. Around this neck of the woods you see folks with external wood fired boilers to heat their homes.

[TimC]

Testing burn time for ~6oz of fuel - 9:45a



Is it burning? Yeah.

[tony.latham]

Testing burn time ...

Could you explain how this little test burner works? I don't see a wick and don't understand what the loop does.

Tony

[troubleScottie]

The rocket stove/Finnish design main advantage is very little to transport ie the pipe, nails, wire and axe/saw. Considerably less than a wood stove. The major disadvantage would a wood fire near a structure.

Air is not the best medium for transferring heat. Water and various glycol solutions are generally better being warmed and transferred. However, liquids are heavier, may require a pump, can spill/leak, and require tight connections.

That is where the diesel/propane heating systems come it. By heating air, they are lighter than a water solution. Using an external combustion chamber, they keep the actual flame outside. Requires fuel and power for ignition/fans. Of course you could go something like the Dickenson solution -- non-electrical heated air AND/OR water/solution system. Obviously there is a price to pay.

The idea of using alcohol as the medium to transfer heat is a bit scary. An alcohol fire can be near invisible.

Using alcohol are the combustible is also a bit scary. I am not aware of the heat generated per weight of fuel. It might be an issue on how much fuel you have to carry.

[TimC]

...That is where the diesel/propane heating systems come it. By heating air, they are lighter than a water solution. Using an external combustion chamber, they keep the actual flame outside. Requires fuel and power for ignition/fans. Of course you could go something like the Dickenson solution -- non-electrical heated air AND/OR water/solution system. Obviously there is a price to pay.

As I mentioned, I like to tinker. I won't be camping in enough cold weather to make a manufactured heating system worth the money. Without any heat source I'm OK down to around 32F.

The idea of using alcohol as the medium to transfer heat is a bit scary. An alcohol fire can be near invisible.
Yup, scary and invisible. As pictured in the last photos both show no flame, but there is a flame.

Using alcohol are the combustible is also a bit scary. I am not aware of the heat generated per weight of fuel. It might be an issue on how much fuel you have to carry.

That is exactly what I am trying to determine... quantity of fuel to burn overnight. I accept it might be prohibitive and expensive. Points are well taken. I see these little alcohol stoves being used for cooking quite often. I'm trying to determine if the capability can be boosted. The Origo 5100 Heat Pal is one pricey proof of concept.

[TimC]

Testing burn time ...

Could you explain how this little test burner works? I don't see a wick and don't understand what the loop does.

Tony

Tony, there are lots of examples of these little stoves on youtube. What I know about the theory is limited. You might want to investigate some of those videos but I'll try.

There are two wicks in the last photos. Each is just a strip of denim fabric stuffed up the copper tube to about where the tubing starts to bend. About an inch and a half of wick extends into the fuel at the bottom.

The loop has a small (.0625) hole on the top of the bottom bend. To prime the stove a small amount of fuel is put below the loop and lit. In my case this is a removable bottle cap. That temporary priming flame heats the tubing and begins to vaporize the fuel coming off the wick. The fuel turns to gas and exits the small hole which acts as the burner. As the flame burns from the hole on the bottom of the loop it continues to heat the tubing which vaporizes more fuel.

You may wonder about the second mason jar ring upside down on the top. That is for a small 8oz jar to screw on to store the stove when not in use.

It's just an experiment, likely to go nowhere. I like to tinker and I'm curious about the amount of fuel that will last for a night. So far the test burn has failed to burn more than an hour with plenty of fuel left in the jar. I've relit it twice and just looked at it and it's out again. I have had the stove inside a large terra cotta pot to try to eliminate the wind blowing it out. Still went out. Not giving up yet.

Yeah, not doing this near any combustibles.
Tim

[iggy3860]

There is some interesting info on this subject on a Kiwi site 'TinyHouse and Offgrid Resources'

He shows how to builds DIY Micro Heater & then, because of a lot of feedback on safety concerns, conducts a Full Safety Test.

I have tried to copy & paste the links but each time I get the same one

Search for 'TinyHouse and Offgrid Resources'

Scroll down until you find 'alcohol stoves'

Click on 'View Full Playlist'

The DIY Micro Heater video is
'DIY Micro Heater- how its made- Greta Thunberg in my shed?' You may have to learn to appreciate Kiwi humor

The Safety Test video is:
DIYAlcohol Camper Heater Full Safety Test

Hope this is helpful

[TimC]

Thanks Iggy. I'll check that out.

I'm beginning to think that my fuel is to far from the burner. Either that or the wick is not efficient enough to wick fuel that distance. The stoves I've seen are smaller Mason jars and the manufactured stove's fuel tank is short and wide.

[tony.latham]

The loop has a small (.0625) hole on the top of the bottom bend.

Gotcha.

And thanks.

Tony

[TimC]

For all those worried about my safety and sanity I have abandoned this experiment. No matter how many times I tried I couldn't get the stove to stay lit for more than an hour in cold (<32f) conditions. It might work in warm weather. Along with other undesirable characteristics of this design I'll move on to some other crazy experiments.