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why waste the heat?

Discussion in 'Home Power and Microgeneration' started by Nomen Nescio, Dec 10, 2006.

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  1. Nomen Nescio

    Nomen Nescio Guest

    why do factories let heat go up the chimney? can't they use it to bake
    bread by having the dough slowly turn inside the chimney and pop out a
    door when it's cooked? you might need to wrap the dough up so it doesn't
    absorb the smoke, but it would still be heated nicely.

    Maybe they could warm water too.

    What do you think?
  2. daestrom

    daestrom Guest

    Well, as another mentioned, a temperature difference is often used to create
    the draft. But if other industries are anything like the thermal power
    plant industry, a great deal of the heat in the chimney *is* used. In power
    plants it isn't used to bake bread, but it is used to pre-heat incoming air
    for the furnace/boiler, and pre-heat the water that is injected into the

    The 'smoke' from many chimneys is mostly water vapor and CO2. The water
    vapor condenses at the outlet forming a miniature cloud. That's what makes
    it visible. Yes, there are also other compounds that are less desirable,
    like SO2 and NOx.

    One problem is that the cost of heating an oven to a modest cooking
    temperature is so easy/cheap to do with a separate fuel source, that the
    money saved using 'chimney heat' isn't really worth it.

  3. true but then that is what fan flues are for .
  4. homeboy465

    homeboy465 Guest

    but it would make sense that this difference could be used you could use the
    heat to then generate pomer of their own and also using in this manner you
    could collect and find other ways to use the emmitions instead of letting
    them distroy the envirlment there has to be a way of using them instead of
    just letting them go to waist and do damage.
  5. You

    You Guest

    EXCEPT, if you rob all the heat from the chimney, to make power, and
    replace it with a Flue Fan, will the Robbed Heat make enough power, to
    run the Flue Fan, and supply some extra for other uses?????????

    NOT likely........
  6. Guest

    The "robbed heat" might be a hundred times more than the fan power,
    eg 10cfmx500F/3.412 = 1465 watts, vs a 15 watt fan.

  7. daestrom

    daestrom Guest

    A good point. But some furnaces already have a 'flue fan', so then it makes
    sense to recover as much heat as practical.

    But depending on the flue gasses, cooling too far can lead to other
    headaches. Condensate can have acids in it that eat away at the chimney;
    tars or creosotes can collect, requiring frequent cleaning.

    This is a sort of 'case-by-case' kind of problem. Not one-size-fits-all.

  8. Yeah, baked in the waste heat of the local creamatorium. Yum.
  9. for ng/lpg condensing boilers the heat exchangers have to be made from
    ss and the condensate drain to the sewer needs to be made in plastic
    pipe (upvc/abs/pp) of cause once it has mixed with other effluent it is
    highly dilute .
    as for flue gases that contain lots of tar (solid fuel) these can be
    reburnt before exiting the appliance .
  10. prob the q you ort to be asking is should we be useing creamatorium at
    all from an enviromental view point ? I dont know the answer to this q .
  11. Jack

    Jack Guest

    I would say yes we should so long as they are fired with biofuels. The body
    itself is carbon neutral.

  12. Jack

    Jack Guest

    now you're thinking outside of the 'box'

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