Enter Boiler Data
Use consistent units. Results appear above this form after calculation.
Example Data Table
| Parameter | Example Value | Unit | Purpose |
|---|---|---|---|
| Steam Output | 8000 | kg/h | Total boiler steam generation rate. |
| Steam Enthalpy | 2778 | kJ/kg | Energy content of produced steam. |
| Feedwater Enthalpy | 419 | kJ/kg | Energy entering with feedwater. |
| Fuel Flow | 550 | kg/h | Hourly fuel input to the boiler. |
| Fuel GCV | 42000 | kJ/kg | Available energy per kilogram of fuel. |
| Stack Temperature | 220 | °C | Helps estimate dry flue gas losses. |
| Calculated Direct Efficiency | 81.70 | % | Example output from the sample values. |
| Calculated Indirect Efficiency | 83.45 | % | Estimated by subtracting losses from 100%. |
Formulas Used
1. Useful Heat Output
Useful Heat Output = Steam Output × (Steam Enthalpy − Feedwater Enthalpy)
2. Fuel Heat Input
Fuel Heat Input = Fuel Flow × Fuel Gross Calorific Value
3. Direct Efficiency
Direct Efficiency (%) = (Useful Heat Output ÷ Fuel Heat Input) × 100
4. Dry Flue Gas Loss
Dry Flue Gas Loss (%) = [Flue Gas Mass × Cp × (Stack Temperature − Ambient Temperature) ÷ Fuel GCV] × 100
5. Indirect Efficiency
Indirect Efficiency (%) = 100 − (Dry Flue Loss + Moisture Loss + Hydrogen Loss + Unburnt Loss + Radiation Loss + Blowdown Loss)
6. Steam to Fuel Ratio
Steam to Fuel Ratio = Steam Output ÷ Fuel Flow
7. Equivalent Evaporation
Equivalent Evaporation (kg/kg fuel) = Useful Heat Output ÷ (Fuel Flow × 2257)
8. Fuel Saving Potential
Target Fuel Flow = Useful Heat Output ÷ [Fuel GCV × (Target Efficiency ÷ 100)]
How to Use This Calculator
- Enter steam output and the enthalpy of produced steam.
- Enter feedwater enthalpy using measured temperature or steam table data.
- Enter actual fuel flow and the fuel gross calorific value.
- Add stack and ambient temperatures for dry flue loss estimation.
- Enter flue gas mass, average Cp, and other estimated losses.
- Set a target efficiency to estimate fuel and cost savings.
- Click the calculate button to show results above the form.
- Use the CSV or PDF buttons to download the results.
Frequently Asked Questions
1. What is boiler efficiency?
Boiler efficiency shows how much fuel energy becomes useful steam energy. Higher efficiency means less wasted heat, lower fuel use, and lower operating cost for the same steam output.
2. Why compare direct and indirect efficiency?
Direct efficiency uses measured heat output and fuel input. Indirect efficiency estimates total heat losses. Comparing both methods helps identify data quality issues and unusual operating conditions.
3. What causes low boiler efficiency?
Common reasons include high stack temperature, excessive excess air, poor combustion, high blowdown, wet fuel, soot deposits, poor insulation, and incorrect burner tuning.
4. Why does stack temperature matter?
Hotter exhaust gases carry more heat out of the system. When stack temperature rises without higher steam production, dry flue gas loss usually increases and efficiency drops.
5. What is steam to fuel ratio?
Steam to fuel ratio expresses how many kilograms of steam are generated from each kilogram of fuel. It is a practical operating indicator for day-to-day boiler performance.
6. Is this calculator suitable for all boilers?
It is useful for many industrial boiler reviews, but actual plant studies may need detailed flue gas analysis, fuel chemistry, blowdown measurements, and steam quality corrections.
7. How accurate are the savings estimates?
Savings estimates depend on realistic target efficiency, fuel cost, and operating hours. They are best used for screening and planning before detailed engineering validation.
8. Should I use gross or net calorific value?
This calculator uses gross calorific value because the direct and indirect formulas here are structured around GCV-based efficiency reporting. Stay consistent across all inputs and reports.