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Need a formula that combines the stack effect + venturi effect to find Q

  1. Jan 6, 2013 #1
    Hi,

    I'm trying to find Q for chimney/stove that looks very similar to the picture attached. I was going to use the formula below, but I realized that it does not account for the venturi effect if a chimney was conical in shape - i.e. smaller at the top vs. the base. Nor does it account for differences in the sizes of the air inlet and outlet.

    Q=CA(sq root(2gH(Ti-To)/Ti))
    http://en.wikipedia.org/wiki/Flue_gas_stack

    where:
    Q = flue-gas flow-rate, m³/s
    A = cross-sectional area of chimney, m² (assuming it has a constant cross-section)
    C = discharge coefficient (usually taken to be 0.65–0.70)
    g = gravitational acceleration at sea level, 9.807 m/s²
    H = height of chimney, m
    Ti = absolute average temperature of the flue gas in the stack, K
    To = absolute outside air temperature, K

    I would like to know if there is a formula to find Q that would allow me to account for the following variables:

    - area of the bottom air inlet
    - area of the top outlet
    - temp inside the chimney
    - temp outside the chimney
    - height of the chimney

    Thanks in advance!!
     
  2. jcsd
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