Calculators · Performance Toolkit
Thermal Efficiency
Estimates fired heater thermal efficiency from stack conditions using a simplified stack-loss method. Enter flue gas O₂, stack temperature, and fuel type to obtain an indicative efficiency figure and loss breakdown.
Inputs
Fuel Type
Flue Gas O₂
%
Typical operating range: 1.0 – 6.0 %
Enter a value between 0.5 and 15 %
O₂ Measurement Basis
Portable analysers typically measure dry; CEMS may be wet or dry — check instrument spec.
Stack Temperature
°C
Typical range: 150 – 350 °C. Measure at the stack base, not the convection outlet.
Enter a value between 80 and 500 °C
Ambient Temperature
°C
Use actual site ambient, not design basis.
Enter a value between −20 and 55 °C
Results
Enter inputs and press
Calculate to see results
Calculate to see results
Calculation method: Simplified stack-loss method based on Siegert / BS 845 principles.
Stack loss is estimated as
(Ts − Ta) × Kf × (1 + EA/100), where Kf is a
fuel-specific flue gas heat coefficient .
Wet O₂ is converted to approximate dry basis using a fixed correction factor of 1.07
.
Radiation and unaccounted losses are fixed at 1.5 %
.
CO and unburned combustibles losses are not included.
⚠ Results are indicative only, based on simplified engineering relationships. Not suitable for use in engineering design, regulatory submissions, energy accounting, or safety-critical decisions. Verify all values with a qualified engineer using site-specific combustion analysis data.
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