wood stove efficiency, and a crazy idea

Discussion in 'Homesteading Questions' started by comfortablynumb, Oct 18, 2005.

  1. comfortablynumb

    comfortablynumb Well-Known Member

    Messages:
    4,808
    Joined:
    Nov 18, 2003
    Location:
    Dysfunction Junction, SW PA
    ok I had this idea today... and i put it in to motion.

    I am amazed, it actually works.

    I screwed steel gutter gaurd mesh strips on my UP pipe off the woodstove, that gets to hot most of the time, and a fan on it doesnt cool it.

    I was wondering how to suck that heat off the pipe and not have to reinvent the wheel...

    about then I had to blow the dust out of my PCs heatsink and it hit me like a train...

    heat sinks...

    so here it is... this stove is about... 6 feet from my desk and I never feel the heat from the stove. NOW.. I have this massive radiant wave on me so bad I have to move the desk. and the stove is birning pretty "nomal", not full blast.. its just cooking a log, low flame... a state where before i wouldnt be etting much heat off the stove.

    try this trick... I cant belive it really works.

    I set a fan behid the pipe to blow thru the mesh and I had to take it off, the heat in here is just to much.

    I serious... this thing radiates heat like you wouldnt believe.
    :happy:

    crazy yeah, ugly, absolutely.
    who cares it works.

    oh cost; 6 bucks. :rock:

    there are four 3 ft strips screwed to this 6" pipe, one on each side and two in front.
    cant put them on the back, the wall would get to hot from the radiant heat.

    I know it works, the pipe temp dropped to @270, it was running at @350+ all the time, so the pipe is cooler.... which is what I was after.... how to cool the pipe and use that wasted heat.

    [​IMG]
     
  2. Ramblin Wreck

    Ramblin Wreck Well-Known Member Supporter

    Messages:
    7,215
    Joined:
    Jun 10, 2005
    Location:
    NW Georgia
    You may want to consider a patent...if its not too late.
     

  3. LOCKHA885

    LOCKHA885 Active Member

    Messages:
    32
    Joined:
    Sep 23, 2005
    Location:
    WV
    This is a great idea and I am saving it to my computer and showing it to my DH tomorrow when he comes home. We are getting ready to install a Wood stove soon, and this is a great idea for keeping the stovepipe cooler and using all that "wasted heat".
    Thanks for sharing.
     
  4. bill not in oh

    bill not in oh Well-Known Member

    Messages:
    1,869
    Joined:
    Jul 27, 2004
    Location:
    Earth
    Great idea...

    At some point (and I have no clue what it exactly is) by lowering the temp of the pipe you should begin to get [more] creosote buildup. My attitude to that, given the extra heat provided is that I'd simply clean the chimney an extra time or two a year....
     
  5. comfortablynumb

    comfortablynumb Well-Known Member

    Messages:
    4,808
    Joined:
    Nov 18, 2003
    Location:
    Dysfunction Junction, SW PA
    I can get the pipe hot... easy. past 400 your buning the crud. it does go up to 600 or 700 for a while when its first fired up.

    my probem was, my fire goes right up the pipe, and the stove doesnt heat up as it should. this was a problem with the grate I solved too today. but while it is on a low burn, the pipe still stays to high, showing me the heat is going upthe pipe and not transfering to the stove metal.

    so, this pulls the heat off that hot pipe while its on low burn and radiates the heat.

    its an old style stove, I can put th pipe out the back but it doesnt draw right unless its out the top.

    I brush out the pipes a few times during the winter anyhow, so i'm not to concerned with creasote... it gets burned out when the stove is first fired up.
    thansk for pointing that out, it is a good point if you have a long pipe prone to build up, this would make it worse.
     
  6. prairie hill

    prairie hill Well-Known Member

    Messages:
    237
    Joined:
    Jul 14, 2002
    Location:
    western nebraska
    Really feel ignorant, but just what about this causes the heat to radiate as you are describing?

    Assuming we can gain some undersrtanding of this, we may do this. We have expanded metal lathe in the barn for if/when we ever finish our firewall behind the stove to look nice... we could use it for the more pressing need of radiating that heat, assuming expanded metal lathe is basically the same as gutter guard.

    Thanks for the idea, and would welcome any further explanation, please!
     
  7. comfortablynumb

    comfortablynumb Well-Known Member

    Messages:
    4,808
    Joined:
    Nov 18, 2003
    Location:
    Dysfunction Junction, SW PA
    it works like the heat sink on a CPU in your computer...
    heat is conducted from the chip to the metal fins of the heat sink, and it in cools the chip, by dissapating heat.

    now this is galvanized steel, different metal wouu;ld work better but.. this is cheap.

    ok, it works like an oron skillet handle... hot right? its not over the flames, the handle is gettig hot from the rest of the skillet...

    this is the same, the mesh is screwed tight to the hot pipe, the mesh "soaks" up the heat, but at the same time has little ability to hold it, and the mesh cools off on the edges as the the centter, in contact with the pipe is heated..

    in short... you got more metal to heat, more hot surface area which means more heat loss.

    its the same reason if you have a hot water radiator system, a long radiator puts out more heat than a short one... you have more hot metal radiating the heat.

    so.. your adding more metal to be heated... bigger pice of hot metal gives off more heat.

    I have noticed, as the fore burned out and I restarted it a fe times, the real effect is when the pipe is HOT.... after a while when the fiore burns down and the pipe cools it doesnt "soak up" the heat very much. The upside for me, anyway, is I can fire up the stove real hot with wood scraps (I have tons) twigs branches kindling ect... for a short hot fire, that has now more radiant heat, thus shorter burn time, thus less wood.
    its pretty nippy out, Ive only burned one bucket of wood tonight since sundown. with the fans blowing the air from room to room its still 70 in here, and about 60 in the far rooms.

    thats even a bit to warm... but I'm tweaking it.

    if I could find copper mesh or sheet, copper would do a better job at heat sinking.
     
  8. Alex

    Alex Well-Known Member

    Messages:
    833
    Joined:
    Mar 20, 2003
    Location:
    Vancouver, and Moberly Lake, BC, Canada
    Heat is conducted (by direct contact), and radiated (by temperature difference between the temperature of flue, and the temperature of the attached mesh), and by convection (gravity air movement from lower area to higher area in the room, or by fan powered air currents). That is how heat is transferred from the flue to the excellent semicircular perforated plate radiator.

    Other metals will have little (very little effect -- they will have only marginal, hardly noticeable effect) on the overall heat transfer and performance of the radiator. The shinny surface is excellent and the rigidity of the steel is good. I would not waste time and money changing the type of metal.

    Once the semi-circular radiators are heated, then they efficiently transfer heat by radiation, and/or by convection if you blow air over them with a fan. Radiant heat is transferred directly to your body and the surrounding. So you don't have to heat the house up too much to FEEL warm. You don't have to accept all the heat loss going out of the building, to feel warm.

    This same radiant heat is what many people like about central wood heat, and cookstoves. You can FEEL the heat. Your radiator is a better, and larger emitter than the single 6" diameter pipe, even though your pipe was hotter.

    This is a good practical idea.

    Alex
     
  9. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

    Messages:
    15,607
    Joined:
    May 10, 2002
    Location:
    Between Crosslake and Emily Minnesota
    Be careful regarding how much heat you extract from your stovepipe. If the stovepipe gets too cool, creosote will condense in it. Use a stovepipe thermometer and keep its temp in the "green zone."
     
  10. comfortablynumb

    comfortablynumb Well-Known Member

    Messages:
    4,808
    Joined:
    Nov 18, 2003
    Location:
    Dysfunction Junction, SW PA
    yup... got 2 on the pipe one on top one on bottom...

    research reasons...
    lol

    pointing the little fan at the BASE of the pipe, where it connects to the stove keeps the top half amore stable temp.
    and the air blowing off is hotter.