Dew Point of Flue Gas Calculator

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Dew Point of Flue Gas Calculator: Prevent Corrosive Condensation

If flue gas or the duct/stack surfaces it contacts drop below the water dew point, moisture condenses, and combined with acidic combustion byproducts, it can rapidly corrode equipment. This calculator computes the dew point temperature from the flue gas's water vapor content using the Antoine equation.

The Formula

PH2O = Water Vapor Mole Fraction × Total Pressure, then Dew Point = B / (A − log10(PH2O in mmHg)) − C (Antoine constants for water)

Worked Example

Flue gas at 101.325 kPa contains 11% water vapor by mole fraction.

PH2O = 0.11 × 101.325 = 11.15 kPa, giving a dew point of approximately 48°C

How to Use This Calculator

  1. Enter the water vapor mole fraction in the flue gas (0-1).
  2. Optionally adjust the total pressure (101.325 kPa, standard atmospheric, by default).
  3. Click Calculate to get the water dew point temperature.

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Use with the Flue Gas Water Vapor Calculator to determine the moisture fraction input, and note that acid dew point runs higher still for sulfur-bearing fuels.