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Physics question: A stove fan .. worth it?

  • 13-11-2016 9:58am
    #1
    celtic_oz
    Registered Users, Registered Users 2 Posts: 1,656 ✭✭✭


    Does a thermo Electric Stove Fan (no external power source) reduce the amount of heat going up the chimney thereby increasing the heat of room and saving on fuel ?


    https://www.youtube.com/watch?v=kgfAAA4Uajc



    if true would it also work for this design where the chimney exits the back of the stove and is directed up behind insulating bricks

    Henley-The-Laune-stove.jpg


Comments

  • #2
    _Brian
    Registered Users, Registered Users 2 Posts: 18,721 ✭✭✭✭_Brian


    I can't see how it stops heat going up the chimney, I think you have that bit wrong.
    I could see them as being good to increase the distribution of heat from a stove within the room.


  • #3
    markfinn
    Registered Users, Registered Users 2 Posts: 266 ✭✭markfinn


    I've been using one since the start of last winter, and had the same questions at the start.

    The theory behind them is that they increase airflow around the stove, increasing the rate at which the heat from the body of the stove is offloaded to the air thereby reducing the heat of the stove's body.

    This in turn means that the heat from the fire is received more rapidly by the body of the stove (greater thermal difference between the burning fuel and the body => more rapid heating of the body), which does suggest to me that less energy is going up the chimney.

    I can't say for sure that it all works as described, but:-
    1. The temperature of the stove body is significantly reduced, from ~250-280 without the fan to ~200-220 with the fan with my usual fuel blend.
    2. The movement of the air at the source of the heat means the room heats faster and more evenly. The ceiling is no longer the first/only area being warmed.


  • #4
    celtic_oz
    Registered Users, Registered Users 2 Posts: 1,656 ✭✭✭celtic_oz


    From a physics point of view if the room is a closed system (except for the chimney), then the only way more heat is left in the room is if the temperature of exhaust gases is lower with the fan ?


  • #5
    SOL
    Registered Users, Registered Users 2 Posts: 1,155 ✭✭✭SOL


    heat-coming-from-radiator.gif




    The fan is probably helping to improve heat distribution instead of having it happen like above.

    In terms of getting more heat out of the stove, this also makes sense but I'd say the faster heating of the room is all to do with distribution rather than improved efficiency of heat transfer. While this is possible, it also could lead to problems - if you lower the combustion environment temperature you may reduce the efficiency of combustion and things wont burn as fully and release as much heat and will cause more soot in your chimney.

    That said I'm not an expert on stoves and I can't see it realistically being a big problem but you should be cautious when changing how your stove works!


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