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Computer Model for Temperature Curves

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  • Computer Model for Temperature Curves

    Here's a graph from a computer simulation on how the heat travels through the thickness of the brick dome during a 2 hour fire, and 8 hours after putting out that fire.

    The model's variables still needs tweaking (thermal capacity of the bricks, temperature of the fire, conductivity of the bricks, the air-brick layer, and the insulation as a whole), but nevertheless, it is already corresponding to several real-life-observations:

    - If you measure with IR, then you might have a fairly quick drop after removing the fire (while the heat is still distributing more evenly through the thickness of the brick). This drop is determined by the duration of the feating fire.
    - Once stabilised, the temperature drops much slower, in this phase, the drop-rate is determined by the exterior insulation.
    - The heat really needs time to travel through the bricks: On the outside, the bricks won't reach their max temperature until well after putting out the fire

    This shows why it makes sense to have a thermocouple one or two inches below the interior surface, as it will better predict at what temperature the oven will stabilize after putting out the fire.

  • #2
    Hi Kvanbael, you might be interested in reading this post I did a few years ago on this subject, it is interesting how these ovens heat up and how they cool down
    ​​​​​​https://community.fornobravo.com/for...586#post157586

    Cheers Doug
    https://community.fornobravo.com/for...-s-48inch-oven

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    • #3
      Interesting thread indeed. Your findings seem to support this simulation. The heat travels slower into the bricks than we think.
      Next up is making measurements to tune the model’s parameters.

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      • #4
        Your simulation looks very reasonable. Taking data from here, http://batchrocket.eu/en/building#bellsizing, they think it is suitable to burn 1-1.5 kg wood (4-6 kW minus efficiency) per m2 of inner dome surface area ( per hour) to charge the bricks. One can then calculate the amount of kWh needed to saturate a specific oven given its brick and floor mass to get the saturation time as a rough estimation. A faster burn only yields a great thermal gradient in the brick and heat loss though the chimney. It seems like very little wood though compared to videos and other recommendations how to fire the wfo.

        ​​​

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