Stack Loss Calculator

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Stack Loss Calculator: The Largest Single Combustion Loss

Stack loss, the heat carried out of a chimney or stack in hot flue gas rather than used productively, is typically the single largest efficiency loss in combustion equipment. This calculator applies the widely used Siegert-type relation to estimate it directly from routine flue gas measurements.

The Formula

Stack Loss% = K × (Tstack − Tambient) / CO2%

Worked Example

Stack temperature is 200°C, ambient is 25°C, CO2 is 10%, with a natural gas K-factor of 0.38.

Stack Loss = 0.38 × (200 − 25) / 10 = 6.65%

How to Use This Calculator

  1. Enter the K-factor for your fuel (typically 0.38-0.42 for natural gas, 0.50-0.56 for fuel oil).
  2. Enter the stack temperature and ambient temperature.
  3. Enter the measured CO2 percentage in the flue gas.
  4. Click Calculate to get the stack loss percentage.

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Feed the result into the Combustion Efficiency Loss Calculator to compute overall combustion efficiency.