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Those in the know??? Question about stove mods?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by BobUrban, Dec 29, 2011.

  1. BobUrban

    BobUrban Minister of Fire

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    Just curious as I have not read or seen anything like this on here but why are there no stoves with radiator fins? It seems that if you had fins on the sides/top of a stove you would be able to gain more heat radiation from the same fuel and therefore be more eficient. Am I missing something or is it just asthestics and maintenance that is the issue?

    As an experienced welder and fabricator it would be pretty easy to fab up something that looks nice(at least to me) and attach it to the stove rather simply. I even thought about the weight issue but that could be rectified with a bolt or slide on part. Some fasionable fin system that just slides onto a light set of angles tacket to the side of the stove with very limited mod to the stove itself. Not anything that would damage or penetrate the stove itself.

    Also, what about something like a 1 or 2" tall grate that is placed on top of the stove. Could still have a cut out for the thermometer to set directly onto the stove but the grate would radiate heat from the top of the stove more eficiently.

    Again, I may be thinking to far outside the box here so correct me please. I have no plan to modify my stove or go total Frankenstove, just trying to gather why this is not something that is offered. Other than cost I cannot see any downside and I have access to steel and welders so cost would be relatively free.

    Help me out with my thinking here - I am just enjoying the heat from my stove, reading Hearth.com and thinking to much.

    Bob Urban

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  2. rdust

    rdust Minister of Fire

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    I'm not 100% sure but I think I remember the new Woodstock stove with the bad name having fins on the back of it? I thought I read that posted somewhere, maybe one of the new owners can comment.

    My stove has what they call a convection deck on top of it, it takes up a little less than half the stove top.
  3. LLigetfa

    LLigetfa Minister of Fire

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    The answer is that most stoves already extract as much heat as necessary without the need for fins. For those that think there is surplus heat, there is the Magic Heat. What heat remains is needed to service the flue draft. The choice of singlewall versus doublewall smokepipe is often based on reclaiming versus preserving heat that is going up the flue.
  4. Peter B.

    Peter B. Feeling the Heat

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    I'm 'with you' in your thinking, though I had a different (or supplemental) approach in mind.

    Cast aluminum vertically finned 'sleeves' to fit over single wall stove pipe... something (sort of) like the image below...

    Tried to find something 'approximate' on the web a while ago, and even asked one or two mfr's if they could/would make up something of the like. I didn't get far.

    Likely, someone here will post to the effect that you'd be robbing the pipe of needed heat... and blah, blah, blah. I'd still like to (be able to) give it a try.

    PB

    -----

    Attached Files:

  5. LLigetfa

    LLigetfa Minister of Fire

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    It is a complex topic WRT how much heat to pull out of the stove and how. There is a lot of ancdotal evidence that the use of blowers to aid in heat removal may take a stove out of the sweet spot causing it to burn dirty.

    In the same vein as a finned stove is the Bullerjan "free flow" stove with convection tubes.

    [​IMG]
  6. LLigetfa

    LLigetfa Minister of Fire

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    If you want to see a finned design, look at this from Harrie Leenders.

    [​IMG]
  7. BobUrban

    BobUrban Minister of Fire

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    Thanks for the input folks - again, just thinking outside the box so to speak. I never considered the "robbing" heat from the draft thing, which is an obvious concern.

    My plan would be to make something that hung from pins or simple hinges and could be removed easily. It would lay flat against the side of the stove and offer more surface area to dispense heat. I would imagine when in peak season with the stove firing full bore this would be ok but shoulder season it would need to be romoved.

    No plans just yet - input here is what I am after and any more examples that others have tried.

    Bob Urban
    ScotO likes this.
  8. Scott2373

    Scott2373 Member

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    On my Jotul Rangeley there are side heat shields that are open at the top and bottom to create a convection effect...and they ARE effective. A lot of heat is transferred out from between the side of the steel firebox and the cast iron shields. They aren't "heat sinks" per se, but do retain heat and disperse it out into the living space similar to what a heat sink would do.
  9. precaud

    precaud Minister of Fire

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    If you've ever used a stove with a cookplate that had ribs on the bottom (inside) surface, and measured the temp difference of the cookplate to the cast iron it sits in, you might want to see those fins on the inside, not the outside, and especially on the top plate. That is where the increased surface area will do the most good.
  10. begreen

    begreen Mooderator Staff Member

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    I seem to recall the Hearthstone Bennington having a heat exchanger built in.
  11. precaud

    precaud Minister of Fire

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    Jotul designed the F100 top plate with this in mind. But it only really helps when the top exhaust outlet is used; the rear one draws the exhaust gasses down away from it.
  12. woodmiser

    woodmiser New Member

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    Keep in mind stoves a certified as designed. Pulling off more heat might take it out of it's efficiency zone too easily.
  13. precaud

    precaud Minister of Fire

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    What's an "efficiency zone" ?
  14. woodgeek

    woodgeek Minister of Fire

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    a picky internet nerd comment: Fins like the above improve convective heat loss, not radiative heat loss.
  15. woodmiser

    woodmiser New Member

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    That would be where the stove is burning the least amount of wood, putting out the least amount of smoke and generating usable heat.
  16. LLigetfa

    LLigetfa Minister of Fire

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    Some stoves have a double-wall construction and air is drawn through the cavity to superheat it for secondary combustion. Modifying such a stove could reduce the heat needed for good secondary combustion.
  17. DevilsBrew

    DevilsBrew Minister of Fire

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    Bob, I am interested to know if you modified the stove. Thanks.
  18. tekguy

    tekguy Feeling the Heat

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    i would think in the case of a house fire or other damage modifying the stove or pipe would give you trouble with your insurance policy
  19. BobUrban

    BobUrban Minister of Fire

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    Never did any mods other than upgrading to a modern EPA stove and relegated the old VC to the fab shop.
  20. mellow

    mellow Resident Stove Connoisseur

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    [​IMG]

    http://www.maderightstoves.com/
  21. begreen

    begreen Mooderator Staff Member

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    Any robbing of heat will have a penalty that needs to be compensated for it the goal is a clean burning system. Rob the stack and you will get creosote accumulation if the chimney gas temp is below 250F. Rob the firebox of heat and you risk incomplete combustion. It can be done, but there are trade offs. One is usually faster combustion in order to keep the burn clean. This is the way masonry stoves are run and it does work.
    ScotO likes this.
  22. Highbeam

    Highbeam Minister of Fire

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    While the fin system extracts heat from the stove using conduction, it releases it using both radiation and convection from hot fins exposed to air.
  23. DevilsBrew

    DevilsBrew Minister of Fire

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    Since there is no mass, would the fins be a decent trade off? Not the best choice but better than nothing?
  24. Highbeam

    Highbeam Minister of Fire

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    Efficiency is defined as the amount of heat delivered to the room per lb of wood. You determine this by measuring the amount of heat wasted up the stack.

    When I burned a non-cat stove I would stare at my flue probe meter and see the 800-1000 degree temps all the time. There is heat being wasted with those flue temps. A magic heat, or other device on the flue, would allow you to reclaim this heat with little or no effect to the fire. Used wisely, you could keep flue temps high enough to prevent cresosote accumulation. This reduction in waste heat is the only way to improve efficiency of the stove.

    If your stove is the proper size then you have nothing to gain from adding fins to the firebox. If you need more btu than your stove can give off at max firebox temp then yes, more HE area will get you more btu. This would not be an efficiency improvement but rather an improvement in heat extraction and you'll need to burn more wood to maintain the same stove temp.
  25. woodgeek

    woodgeek Minister of Fire

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    Re the 'made right'...yuck. The emissivity of aluminum (or aluminum oxide) is very low....shiny Al is a poor radiator surface. Sounds like a cheaply made low mass steel stove wrapped in cheap extruded Al fins and thin gauge Al sheet. Wonder how it looks after a couple burns...

    I also liked the bit about recommending an open flue cap....the ones with mesh clog up too fast!! :rolleyes:

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