Improving Out door wood stove efficiency

[Old F]

Improving  Out door wood stove efficiency

A resent  post showed  this to be a hot topic .  : )

Ok to start we know that the over all system  efficiency  sucks.

 Average  about  %50 more or less your mileage my very.

So lets put are heads together a see what can be done to improve  it.

One thing that was pointed out  is that you are heating the hole house evenly  24/ 7.

This means more wood being burned .

 So first thing I going to do for mine is to replace the in house thermostat  with a programmable set back model.

   Lowering the temperature at night means  less wood burned. Should pay for its self  quickly.

Old F

[brians]

ok this is what i had planed . i have 6 foot long by 2 foot pipe   i plan on making a heater out of that .going to be outside because of size anyway i was going to put sand around the pipe to keep heat .1 in copper pipe will run the lengh of fire box. for  hot water and radint heat . i also am going to bulid a hood over the fire box to chatch the heat and send it to where every i need it . the heater buliding will probley be made out of 8 in block filled with sand .well this is what i had in mind so what do you all think.

[brians]

i went and took some pics what i was talking about here they are

[Old F]

Brians

I believe you will get there.  Back in the 70s a set of plans came out

For a stove that had a large fire box that was surrounded by 8 or 12 tons of sand with coils of copper tubing buried  in  it .

 You would load it up and let the  fire roar  this way you would get a clean high temp burn.  

 The sand stored the heat .

They claimed you only had to fire it once  every three days  to heat your whole house.

   With  the size of your fire box you mite have to fire once a day with 2 or 3 ton  of sand storage.

   This mite be a better way to for home builders than a water  based  stove like my Wood Master.

[ignesandros]

Would you be wrapping the copper pipe around the bigger pipe? In what way did you plan on regulating your water temperature?

You may want a slightly larger diameter burn chamber so there's plenty of air space, not to mention save you time splitting logs.

Is this going to be naturally aspirated? As I mentioned in another thread, imparting heat from the exhaust gases into intake air heats the process exponentially. In addition, it burns the wood more efficiently.

I like the sand idea, but it's just as practical to use dirt. Fire brick (like the 4x13in variety)in at least one layer around the burn chamber is advisable, though.

Make sure the piping for the flew gas is resistant to corrosion so you can clean out the creosote, rosin, and other wood by-products with proper cleaners come summer. This is especially essential if you're burning green wood, pine, and other sappy woods.

-Andrew

[richhagen]

Heat transfer occurrs by conduction, convection, and radiation.  For an outdoor wood furnace you need to limit all of those losses to the environment at the outdoor furnace, and through the tubing uses to transfer the working fluid into the house.  For an inside furnace, those losses still end up as heat in your house and are no big deal.  For an outdoor furnace you would need well insulated tubing, and thick insulation around your fire box to minimize the heat transfer to the outside environment.  A counter flow air to air heat exchanger for incoming and exhaust air from the firebox to minimize convective losses out the stack.  You still won't likely beat an inside wood stove for efficiency, since the only losses there are the convective losses out the stack, but it might be worth it for the safety of not having a fire inside in some cases (at least from your insurers point of view).  

[brians]

ignesandos i live next to a ckeek i will use a water wheel to turn a pump to cirlate the water and use pressure vale and hot water heater tank i have 3 bildings i plan to use raterators for heat in them with 12 volt fan this will take some hear away i hope i was just going to place pipe in the sand about 2 feet from fire box . i was going to use house air as fresh air intake this will cirlate air . i also burn coal here in south carlina as i work long days it will burn hot but slow . i dont have everything figure out yeat that why i depend on this web site to help me think of new wasy  to do things thanks guys keep on thinking

[elvin1949]

Old F

 Wasn't that called a  Hasha.

The mother earth news had something about it i think

later

Elvin

[mikey ny]

 Hello,

   I have an out door boiler in my detached garage. I have many improvements to make to it this year. The first thing I will do is put in a better chimny, maybee a 6 inch steel pipe, make a heat exchanger around it and pipeit into the combustion air intake, because most of the time it sucks in very cold outside air for combustion air.

                                                       Mike

[electrondady1]

i'm not shure why these out door furnaces are considered waste full or inefficient . is it because they are cycleing on and off ?  with a little air added you can get old wet leaves to burn with a nice blue flame. i thought that would be good!