No Pressure Steam for moving heat...

OK, crazy idea. Boil water via rocket stove, channel the steam into a relatively large diameter pipe,condense the water into a steel tank which is located in the area you want to heat.
If the area you want to heat is located above the rocket stove, the steam will rise to the condensing steel tank and the condensed water can drain back to the boiling vessel.
If the rocket is located on the same level or higher, an exhaust fan can move the steam and a pump can move the condensed water.

In a green house a with a subterranean heating and cooling system, the rocket generated steam could be directed into the system, super charging the soil with heat.

Why do this? Well If one needs to have a rocket in in one place and move the heat to another place, actively encouraging the creation of steam in a no pressure system could be a way to use the energy density of water to move that heat.

I need such a system. I can't have rocket in the house, but I can move the heat inside. Hot air into the forced air furnace return air duct, preheating the distributed air.
But hot air is a terrible way to store heat. Hot water could work, but risks steam explosion. So, use a no pressure system, which might steam but not explode.
But if yo are going to allow steam, why not encourage it? Water to steam and steam to water are phase changes, potentially efficient ways to store and move heat.

OK, enough crazy talk, lets hear some feedback!

I think the main issue would be to vent it to the outside, so that you don't end up with moisture issues inside.

A simple experiment using any electric kettle that has a spout on it, could help you see just how large a condensing surface would be needed to prevent steam from leaving the condenser before it's done. I think you'd find that it may require a very large condenser.

A hot water system that is open to the atmosphere outside, is unlikely to lose vast quantities of heat. If your Reservoir is relatively large, firing can be reduced as you near the boiling point. Many older hot water systems we're open to the atmosphere.

Hello William, a steam heating system is certainly possible.
I will try to point out the difficulties, that I am aware of:
- It requires distilled water (otherwise you end up with minerals in your stove pipe, blocking the heat transfer).
- An open system will loose steam over time unless you keep the energy in the system constant (which is impossible). -> refilling with distilled water
- Some steam will condense in the pipes and this water has to flow either downwards with the steam or back to the rocket stove. It should not be allowed to collect somewhere else and block the pipe.
- The pipes and connections in and round the rocket stove have to tolerate the highest temperatures that it might produce.
- Controlling the pumps might be tricky. Too slow and all the water is boiled; too fast and hot water is flowing out of the rocket stove.

I would suggest an open gravity hot-water system instead. If you don't want pipes thick enough to have sufficient low flow resistance for a gravity system, a (temperature controlled) pump will do the job.
You still need to pay attention to the water and contained minerals. To be save, make it slightly alkaline (chalk/lime), boil it and let it rest. Everything that is still liquid should remain so.

If you don't want to risk overheating, you could use thick pipes in your rocket stove (after the heat riser) and a big (possibly insulated) water tank above.
From there you pump the water to the places that you want to heat.

If this isn't save enough, put the pipes to and from the rocket stove downwards and add an open buffer somewhere. When the water overheats, the steam displaces the water downwards out of the rocket stove and into the buffer.
The leftover steam insulates the remaining water in your system. But make sure that the pipes that might contain steam can handle the heat and the buffer container is can take the displaced water.


greetings, Sebastian

Thank you for the feedback!
I am not sure if distilled water is an affordable option.
Maybe an occasional cleaning would suffice.
I had envisioned a 1.5" pipe passing through the return airduct on a downward slant toward a 55 gallon drum .
That drum would be set smack-dab against the vertical portion the return air duct and wrapped in insulation except for the side up against the duct. If I could find a square tank it would be better be better for heat transfer.
A pump would tansfer the (relatively) cooled water back to rocket stove via the same return air duct run,in order to remove the last bit of heat from it.

The problem I see with running through the return air duct is possible condensation.

This design could be built as a hot water system,but it's the potential for not needing a pump and the magic of phase change that intrigue me.

I intend to set the rocket boiler inside a semi detached sunspace and siphon off the solar/wood heated air for immediate heat, with the heated water being the thermal mass.

There's no need for distilled water to be expensive. You could simply have another expendable container that occasionally sits on the stove and boils into a condensing barrel, to produce a regular supply of distilled water.

Systems requiring constant flow can be more troublesome than batch systems, if there are pumps. Hopefully, you can situate your rocket beneath the radiator. Then the whole system will flow automatically. You would need to check the water level occasionally.

William Bronson wrote: If I could find a square tank it would be better be better for heat transfer.

http://donkey32.proboards.com/thread/1817/starting-build-220mm-rocket-double

William Bronson wrote:Maybe an occasional cleaning would suffice.

Our water is rich in carbonates which results in deposits in every place that gets into contact with hot water. Pipes, Kettle, hot water boilers, ... Now I am a paranoid about it.
If you don't have these problems, you could try it with untreated water.

William Bronson wrote:I had envisioned a 1.5" pipe passing through the return airduct on a downward slant toward a 55 gallon drum .
That drum would be set smack-dab against the vertical portion the return air duct and wrapped in insulation except for the side up against the duct. If I could find a square tank it would be better be better for heat transfer.
A pump would tansfer the (relatively) cooled water back to rocket stove via the same return air duct run,in order to remove the last bit of heat from it.

The problem I see with running through the return air duct is possible condensation.

The water is boiling in the drum, therefore the temperature of the air stream after it will be above 100°C (energy transfer requires a temperature difference). And unless your return air duct is extremely bad insulated and creates a lot of turbulence, chances are the air inside is still above 100°C.
So you won't get condensation there. But too much condensed water running into there could still cause problems.

William Bronson wrote:This design could be built as a hot water system,but it's the potential for not needing a pump and the magic of phase change that intrigue me.

I intend to set the rocket boiler inside a semi detached sunspace and siphon off the solar/wood heated air for immediate heat, with the heated water being the thermal mass.

Is the rocket stove in a location, lower than the places where the steam is supposed to condense?

The rocket would be located just outside of the back wall of my house. The return air duct starts just on the other side of the wall and travels almost 20 feet in a straight line before turning down to meet up with the furnace.
An exhaust fan would be needed to insure the steam ran down to the condensing tank, yet another reason to avoid the steam system and use the hot water idea.

William, you may want to check out this link. Many Homesteaders and off-grid people have considered a design like this. when working with wood heated water one MUST UNDERSTAND THE DANGERS. With that said good luck and know our forefathers have done it before us for many years without the technology of safety valves we have today.

http://solarhomestead.com/using-your-wood-stove-to-heat-water/

One idea may be to use the above link idea and run copper inside with baseboard style fins on them to help radiate the heat.