Flue Gas Temperature Calculator
How Much a Heat Exchanger Cools Flue Gas
As flue gas passes through a boiler, economizer, or heat recovery unit, it gives up heat and drops in temperature. This calculator finds that exit temperature from the heat absorbed and the gas flow's mass and specific heat.
The Formula
Exit Temp = Inlet Temp − (Heat Absorbed / (Mass Flow × Specific Heat))
Worked Example
Flue gas entering at 350°, with 40 kW absorbed from a flow of 800 kg/hr (0.222 kg/s) at 1.05 kJ/kg.K:
Exit Temp = 350 − (40 / (0.222 × 1.05)) ≈ 178.5°
How to Use This Calculator
- Enter the Inlet Flue Gas Temperature.
- Enter the Heat Absorbed by the heat exchanger in kW.
- Enter the Gas Mass Flow rate in kg/hr.
- Optionally adjust the gas Specific Heat (defaults to 1.05 kJ/kg.K).
- Select Calculate to get exit flue gas temperature.
Related Calculations
Check if this exit temperature risks condensation in the Dew Point of Flue Gas Calculator, or find draft at this temperature in the Stack Draft Calculator.