Calculator Inputs
Formula Used
For a fuel represented as CxHyOzSw:
Total theoretical energy = |ΔHcomb| × moles of pure fuel
ΔHcomb = Σ(n × ΔHf,products) − Σ(n × ΔHf,reactants)
Usable energy = Theoretical energy × combustion efficiency
CO₂ = x × fuel moles
H₂O = (y/2) × fuel moles
SO₂ = w × fuel moles
How to Use This Calculator
- Enter the fuel name and elemental composition using carbon, hydrogen, oxygen, and sulfur counts.
- Leave custom molar mass empty to let the calculator derive it from the formula.
- Choose whether your amount is entered by mass or by moles, then select the matching unit.
- Set fuel purity, combustion efficiency, and excess air to reflect real operating conditions.
- Use the direct method when you already know the combustion enthalpy in kJ/mol.
- Use the Hess method when you want the page to derive combustion enthalpy from formation enthalpies.
- Click the calculate button to display the full results block above the form.
- Use the CSV or PDF buttons to export the result table for reports or documentation.
Example Data Table
| Fuel | Formula | Approx. HHV (kJ/mol) | Molar Mass (g/mol) | Typical Use |
|---|---|---|---|---|
| Methane | CH₄ | 890.3 | 16.043 | Natural gas combustion studies |
| Propane | C₃H₈ | 2220.0 | 44.097 | LPG burner and heater estimates |
| Ethanol | C₂H₆O | 1366.8 | 46.069 | Biofuel and lab fuel analysis |
| Benzene | C₆H₆ | 3267.0 | 78.114 | Organic combustion comparison |
These values are rounded examples for quick testing. Use verified laboratory or engineering data for final design decisions.
FAQs
1. What does this calculator estimate?
It estimates combustion energy, oxygen demand, air requirement, and major product formation. It also converts usable energy into kJ, MJ, kWh, and BTU for easier engineering review.
2. Why are purity and efficiency included?
Purity adjusts the actual amount of combustible material. Efficiency estimates how much theoretical energy becomes useful output after practical losses inside a burner, engine, or heater.
3. What is the difference between HHV and LHV?
HHV includes the heat recovered when water vapor condenses. LHV excludes that recovered condensation heat. Choose the basis that matches your reference data or equipment rating method.
4. When should I use the Hess method?
Use the Hess method when you know formation enthalpies and want the page to derive combustion enthalpy from thermochemical data rather than entering a direct heating value.
5. Does this handle sulfur-containing fuels?
Yes. Sulfur atoms increase oxygen demand and produce SO₂ in the simplified output model. This helps compare cleaner fuels with sulfur-bearing alternatives in a quick screening workflow.
6. Why can oxygen demand become invalid?
If the entered formula contains too much oxygen relative to combustible elements, the stoichiometric expression may become zero or negative. That indicates the composition should be checked.
7. Are the emissions values complete?
No. The page estimates major stoichiometric products only. It does not model NOₓ, unburned hydrocarbons, soot, dissociation effects, or detailed equilibrium chemistry.
8. Can I use this for process design?
It is useful for preliminary sizing, education, and comparison. For final design, confirm inputs with trusted fuel data, operating conditions, and a more detailed combustion model.