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Heat of Combustion Calculator

Ready to calculate
HHV = LHV + n_w·M_w·ΔH_vap.
10 Fuel Presets.
kJ · kcal · BTU Units.
100% Free.
No Data Stored.

How it Works

01Pick Fuel + LHV

Choose from 10 preset fuels (H₂, methane, propane, diesel, etc.) or enter custom LHV in kJ/g, MJ/kg, kcal/g, or BTU/lb

02Set ΔH_vap of Water

Default 2257 kJ/kg at 25 °C — the heat released when water vapor condenses back to liquid

03Enter Moles

Moles of water vaporized and moles of fuel combusted — from your balanced combustion equation

04HHV = LHV + Δ

Get higher heating value (gross) per mole and per gram of fuel, plus total scenario energies

What is a Heat of Combustion Calculator?

Heat of combustion is the central thermodynamic property of any fuel — the amount of energy released when one unit (mole or kg) of fuel burns completely in oxygen to form CO₂ and H₂O. But there's a subtlety that trips up every chemistry student: the value depends on whether the product water exits as liquid or vapor. The "higher" value (HHV — also called gross heating value) assumes water condenses back to liquid and gives back its 2257 kJ/kg of vaporization heat. The "lower" value (LHV — also called net heating value) treats water as remaining a vapor in the exhaust, the practical case in real engines and boilers. Our Heat of Combustion Calculator computes HHV = LHV + (nwater/nfuel) × Mwater × ΔHvap with full unit flexibility, 10 fuel presets, and complete energy accounting for both per-mole and per-mass outputs.

Just pick a fuel from the 10-entry preset (hydrogen, methane, ethane, propane, butane, pentane, paraffin wax, kerosene, diesel, natural gas) — and the calculator auto-loads its standard LHV from CRC Handbook tables, the molar mass, and the stoichiometric n_water/n_fuel ratio for complete combustion. Then enter the moles of water vaporized and the moles of fuel combusted (defaults to 1 mole fuel and the matching water count). The calculator computes the additional energy from water condensation: ΔE = n_water × M_water × ΔH_vap (in kJ), divides by n_fuel to get a per-mole-fuel value, and adds to the LHV per mole to give the HHV. Output: HHV per mole of fuel (kJ/mol), HHV per gram (kJ/g = MJ/kg), the HHV/LHV ratio (typically 105-118%), and the total energy released for your specific scenario.

Designed for chemistry students learning thermochemistry and Hess's Law, mechanical engineers calculating boiler and engine efficiency, energy analysts comparing fuels (hydrogen vs natural gas vs gasoline), environmental scientists computing CO₂ emissions per unit energy, and HVAC engineers sizing combustion equipment, the tool runs entirely in your browser — no data is stored or transmitted.

Pro Tip: Pair this with our Combustion Reaction Calculator to balance the combustion equation first (gives you the n_water/n_fuel ratio), or our Molecular Weight Calculator to find the molar mass of your custom fuel.

How to Use the Heat of Combustion Calculator?

Pick a Fuel: Choose from 10 preset fuels — hydrogen (LHV 120 MJ/kg, M = 2.016), methane (50.0, 16.04), ethane (47.5, 30.07), propane (46.4, 44.10), butane (45.7, 58.12), pentane (45.4, 72.15), paraffin wax (42.0, 352.7), kerosene (43.0, 170.3), diesel (42.6, 167.3), natural gas (47.1, ~17.0). The calculator auto-fills LHV, molar mass, and the stoichiometric n_water/n_fuel ratio for complete combustion.
Verify or Override LHV: The lower heating value of the fuel — energy released per unit fuel mass when water exits as vapor. Choose units: kJ/g (= MJ/kg), kcal/g, or BTU/lb. Editing the LHV automatically switches the fuel to "Custom".
Set ΔHvap of Water: The latent heat of vaporization of water. Default 2257 kJ/kg at 25 °C (= 40.66 kJ/mol). Use 2260 kJ/kg at 100 °C if computing for hot exhaust gases. Supports kJ/kg, kJ/g, kcal/kg, and BTU/lb.
Enter Moles of Water Vaporized: Total moles of water produced and present as vapor in the combustion exhaust. From the balanced combustion equation: methane gives 2 mol H₂O per mol CH₄; propane gives 4 per mol; cyclohexane gives 6.
Enter Moles of Fuel Combusted: The amount of fuel burned in your scenario (e.g., 1 mol for the per-mole HHV; 100 mol for an industrial run).
Press Calculate: Get HHV per mole of fuel (kJ/mol), HHV per gram (kJ/g = MJ/kg), the HHV/LHV ratio, the total energy at LHV basis vs HHV basis, and the contribution of water condensation to the total.

How is heat of combustion calculated?

The HHV ↔ LHV distinction is so fundamental that every combustion engineer must internalize it. The whole formula reduces to one principle: when water exits as vapor (LHV) you "lose" the heat of vaporization; when it condenses back to liquid (HHV) you recover it. Here's the complete framework:

The IEA, EPA, and DOE in the US use HHV by default; most European and Asian agencies use LHV. Knowing how to convert between them is essential for any cross-border energy analysis.

The Conversion Equation

For a fuel that produces n_water moles of H₂O per mole of fuel during complete combustion:

HHV − LHV = (nwater / nfuel) × Mwater × ΔHvap(water)

where M_water = 0.018015 kg/mol and ΔH_vap = 2257 kJ/kg at 25 °C. The product on the right is in kJ per mole of fuel.

The Two Definitions

  • HHV (Higher Heating Value, gross): Total heat released when products are returned to 25 °C and water condenses to liquid. The value measured directly in a bomb calorimeter (constant volume, isothermal). Used by US energy agencies, chemists doing Hess's Law cycles.
  • LHV (Lower Heating Value, net): Heat released minus the latent heat that would be needed to evaporate the product water. The practical value for engines and boilers where water exits as vapor in the exhaust stream. Used by European energy agencies, mechanical engineers calculating efficiency.

Why the Difference Depends on H/C Ratio

The HHV − LHV gap is proportional to the moles of water produced per unit fuel. For complete combustion of a generic hydrocarbon CxHy: CxHy + (x + y/4) O₂ → x CO₂ + (y/2) H₂O. So n_water = y/2 per mole of fuel.

  • Hydrogen (H₂): n_water = 1 per mole H₂. HHV/LHV ≈ 1.18 (huge gap — hydrogen produces only water).
  • Methane (CH₄): n_water = 2 per mol. HHV/LHV ≈ 1.11.
  • Propane (C₃H₈): n_water = 4 per mol. HHV/LHV ≈ 1.09.
  • Octane (C₈H₁₈): n_water = 9 per mol. HHV/LHV ≈ 1.07.
  • Carbon (C): n_water = 0. HHV = LHV exactly (no water produced).

Per-Mole vs Per-Mass

The calculator handles both conventions:

HHV (kJ/mol fuel) = LHV (kJ/g) × Mfuel (g/mol) + (nwater/nfuel) × Mwater × ΔHvap

HHV (kJ/g fuel) = HHV (kJ/mol) / Mfuel

Numerically kJ/g = MJ/kg, so the per-mass HHV is also the energy density in MJ/kg — useful for comparing fuels on a "per-tank-of-gasoline" basis.

Total Energy for n_fuel Moles Burned

Total energy at HHV basis (kJ): E = nfuel × HHVper mol. The total water contribution is:

Econdensation = nwater × Mwater × ΔHvap

For 1 mole of methane: E_LHV ≈ 50 × 16 = 800 kJ; E_condensation = 2 × 0.01802 × 2257 = 81 kJ; E_HHV = 881 kJ. So HHV = 55 kJ/g (vs LHV 50 kJ/g) — a 10% bonus.

When to Use Which

  • Use HHV for: bomb calorimetry data, Hess's Law thermochemistry, US energy statistics (EIA, DOE, EPA), comparing fuels on a "what's the maximum energy" basis.
  • Use LHV for: engine and boiler efficiency calculations, exhaust-temperature analysis, European energy statistics (IEA), comparing fuels on a "what energy actually drives my machine" basis.
  • The 5-15% gap matters: a "55% efficient" gas turbine on HHV basis is "61% efficient" on LHV basis — the same machine, two different conventions. Always state which one.
Real-World Example

Heat of Combustion Calculator – Worked Examples

Example 1 — Methane (Natural Gas Main Component). Combustion: CH₄ + 2 O₂ → CO₂ + 2 H₂O. So n_water/n_fuel = 2.
  • LHV = 50.0 kJ/g (CRC reference); M_fuel = 16.04 g/mol → LHV per mole = 50.0 × 16.04 = 802 kJ/mol.
  • Water condensation per mole fuel: (2 mol H₂O) × (0.018015 kg/mol) × (2257 kJ/kg) = 81.3 kJ/mol fuel.
  • HHV per mole = 802 + 81.3 = 883.3 kJ/mol.
  • HHV per gram = 883.3 / 16.04 = 55.1 kJ/g = 55.1 MJ/kg.
  • Reference: literature HHV(methane) = 55.5 MJ/kg. ✓ Matches within 1%.
  • HHV/LHV ratio = 55.1/50.0 = 1.10 = 110%. Methane has a 10% gap because every mole produces 2 moles of water.

Example 2 — Hydrogen (Highest HHV/LHV Gap). Combustion: 2 H₂ + O₂ → 2 H₂O. So n_water/n_fuel = 1.

  • LHV = 120 kJ/g (the highest gravimetric energy density of any fuel); M_fuel = 2.016 g/mol → LHV per mole = 120 × 2.016 = 241.9 kJ/mol.
  • Water condensation: (1) × (0.018015) × (2257) = 40.7 kJ/mol fuel.
  • HHV per mole = 241.9 + 40.7 = 282.6 kJ/mol.
  • HHV per gram = 282.6 / 2.016 = 140.2 kJ/g = 140 MJ/kg.
  • HHV/LHV ratio = 140/120 = 1.17 = 117%. Hydrogen has the LARGEST HHV-LHV gap because it's pure water-producer (no CO₂).
  • This is why fuel-cell efficiency is often quoted on HHV vs LHV basis — the 17% gap matters enormously: a 60% LHV fuel cell is only 51% HHV efficient.

Example 3 — Diesel. Average diesel ~C₁₂H₂₃, so n_water/n_fuel ≈ 11.5; M_fuel ≈ 167.3 g/mol; LHV ≈ 42.6 kJ/g.

  • LHV per mole = 42.6 × 167.3 = 7,127 kJ/mol.
  • Water condensation: 11.5 × 0.018015 × 2257 = 467.6 kJ/mol fuel.
  • HHV per mole = 7,127 + 468 = 7,595 kJ/mol.
  • HHV per gram = 7,595 / 167.3 = 45.4 kJ/g = 45.4 MJ/kg.
  • HHV/LHV ratio = 45.4/42.6 = 1.066 = 107%. Diesel has a small gap because it's hydrogen-poor (lower H/C ratio than methane).

Example 4 — Real-World Total Energy. A 50-liter (≈ 42 kg) diesel tank burns completely.

  • Moles of diesel: 42,000 g / 167.3 g/mol = 251 mol.
  • Moles of water vaporized: 251 × 11.5 = 2,887 mol.
  • Total LHV energy: 251 × 7,127 = 1.79 GJ = 497 kWh.
  • Water condensation heat: 2,887 × 0.018015 × 2257 = 117 MJ = 33 kWh.
  • Total HHV energy: 1.79 + 0.117 = 1.91 GJ = 530 kWh.
  • A diesel engine at ~35% efficiency delivers about 1.79 × 0.35 = 0.63 GJ of useful work — about 174 kWh. The other 65% leaves as heat in the exhaust and cooling water (most of it the LHV − engine_work portion).

Who Should Use the Heat of Combustion Calculator?

1
Chemistry Students: Solve thermochemistry problems on heat of combustion; convert between bomb calorimeter (HHV) and engine-efficiency (LHV) values; use Hess's Law with consistent definitions.
2
Mechanical Engineers: Calculate boiler, furnace, and engine efficiency on the correct LHV basis; spec exhaust heat exchangers; size condensing furnaces (which recover the HHV-LHV gap).
3
Energy Analysts: Compare fuels (gasoline 44 MJ/kg vs natural gas 50 MJ/kg vs hydrogen 120 MJ/kg) and convert between HHV (US convention) and LHV (international convention) for cross-border reporting.
4
Environmental Scientists: Compute carbon intensity (kg CO₂ / kWh) for fuel comparison; the HHV/LHV choice affects emission factors by 5-18%.
5
HVAC Engineers: Specify condensing vs non-condensing boilers — only condensing units capture the HHV-LHV gap (extra 10-12% efficiency for natural gas).
6
Pharmaceutical / Food Calorimetry: Bomb calorimetry of biological samples reports gross calorie content (HHV); subtract water vaporization to get the metabolizable energy (closer to LHV).

Technical Reference

Why Two Definitions Exist. Bomb calorimeters operate at constant volume and condense the water — the natural setup gives HHV directly. Engines and boilers operate at constant pressure (atmospheric) with water exiting as vapor — the natural quantity is LHV. Both are correct measures of "heat of combustion"; the choice is purely operational. ISO 1928, ASTM D240, and ASTM D4809 standardize the bomb-calorimeter measurement; the conversion to LHV is then performed mathematically using the formula HHV − LHV = (n_w/n_f)·M_w·ΔH_vap.

Standard Heat of Vaporization of Water.

  • At 25 °C: 2,442 kJ/kg (44.0 kJ/mol) — the standard "ΔH_vap°" for thermochemistry tables.
  • At 100 °C: 2,257 kJ/kg (40.66 kJ/mol) — the latent heat at boiling. Most engineering tables use this value (this is the calculator's default).
  • At 0 °C: 2,501 kJ/kg (45.05 kJ/mol).

The HHV-LHV gap is computed at the temperature where the water is assumed to "condense back" — typically 25 °C for thermochemistry, 100 °C for boiler engineering. The 10% difference between these conventions can shift the gap by ~0.5 MJ/kg.

Standard LHV Values (CRC Handbook, 25 °C, 1 atm):

  • Hydrogen (H₂): LHV = 120.0 MJ/kg, HHV = 142.0 MJ/kg (HHV/LHV = 1.18)
  • Methane (CH₄): LHV = 50.0 MJ/kg, HHV = 55.5 MJ/kg (1.11)
  • Ethane (C₂H₆): LHV = 47.5 MJ/kg, HHV = 51.9 MJ/kg (1.09)
  • Propane (C₃H₈): LHV = 46.4 MJ/kg, HHV = 50.4 MJ/kg (1.09)
  • Butane (C₄H₁₀): LHV = 45.7 MJ/kg, HHV = 49.5 MJ/kg (1.08)
  • Octane (C₈H₁₈, gasoline): LHV = 44.4 MJ/kg, HHV = 47.9 MJ/kg (1.08)
  • Diesel (~C₁₂H₂₃): LHV = 42.6 MJ/kg, HHV = 45.5 MJ/kg (1.07)
  • Coal (anthracite): LHV = 27 MJ/kg, HHV = 28 MJ/kg (1.04)
  • Wood (dry): LHV = 18 MJ/kg, HHV = 20 MJ/kg (1.11)

Connection to Other Quantities. The standard enthalpy of combustion ΔH_combustion equals −HHV (because combustion releases heat, ΔH is negative). For methane: ΔH_c° = −890 kJ/mol = −55.5 MJ/kg. The Gibbs free energy of combustion ΔG_c° includes the entropy term −T·ΔS — for hydrogen ΔG_c° (water as vapor) = −229 kJ/mol vs ΔH_c° = −242 kJ/mol, the difference being the lost entropy on combining H₂ + ½O₂ → H₂O.

Engine and Boiler Efficiency Conventions.

  • Internal combustion engines (gasoline, diesel): Efficiency typically reported on LHV basis (~25-45%); the exhaust water leaves as vapor and the latent heat is "lost".
  • Power plant boilers: Conventional boilers report LHV efficiency (~35-45%); condensing boilers (HVAC, district heating) capture the latent heat and report HHV efficiency closer to 90-95%.
  • Fuel cells: Often reported as both — a hydrogen PEM fuel cell at "60% LHV" is 51% on HHV basis. Always check.
  • US natural gas industry: Reports HHV in BTU (1 therm = 100,000 BTU = 105.5 MJ); residential gas bills use HHV.

Carbon Intensity (Climate Implications). Per kg fuel: methane → 2.75 kg CO₂; gasoline → 3.10 kg; diesel → 3.16 kg; coal → ~3.0 kg (varies by rank). Per MJ of HHV energy: methane → 50 g CO₂/MJ; gasoline → 65 g/MJ; diesel → 70 g/MJ; coal → 90-100 g/MJ. Hydrogen → 0 g/MJ at point of use (but depends on production pathway: green H₂ ~0, gray H₂ from steam reforming ~80 g/MJ).

Key Takeaways

Heat of combustion comes in two flavors that differ by 5-18% depending on the fuel's H/C ratio: HHV (higher / gross) assumes water condenses back to liquid in the exhaust; LHV (lower / net) treats water as vapor (the real-engine case). The conversion is universal: HHV = LHV + (nwater/nfuel) × Mwater × ΔHvap. Hydrogen has the largest HHV/LHV gap (~17%); pure carbon has zero gap. Use HHV for bomb calorimetry and US energy reporting; use LHV for engine/boiler efficiency and international (IEA) reporting. Use the ToolsACE Heat of Combustion Calculator with 10 fuel presets, four energy-per-mass units, and complete energy accounting (per mole, per gram, total scenario). Bookmark it for chemistry homework, combustion engineering, energy comparisons, and any time you need to convert between HHV and LHV with confidence.

Frequently Asked Questions

What is the Heat of Combustion Calculator?
It computes the higher heating value (HHV, gross) from the lower heating value (LHV, net) of a fuel using HHV = LHV + (nwater/nfuel) × Mwater × ΔHvap. Inputs: fuel preset (10 options) or custom; LHV in kJ/g, MJ/kg, kcal/g, or BTU/lb; ΔH_vap of water in kJ/kg, kJ/g, kcal/kg, or BTU/lb (default 2257 kJ/kg at 25 °C); moles of water and moles of fuel in mol/mmol/kmol; molar mass of fuel in g/mol (auto-filled from preset).

Output: HHV per mole and per gram of fuel; Δ between HHV and LHV; HHV/LHV ratio; total energy released for your specific scenario at both LHV and HHV bases; fuel mass burned and water mass produced. Designed for chemistry students, mechanical engineers, energy analysts, environmental scientists, and HVAC engineers. Runs entirely in your browser — no data stored.

Pro Tip: Use our Combustion Reaction Calculator to balance the equation first.

What's the difference between HHV and LHV?
HHV (Higher Heating Value, gross): total heat released when combustion products are returned to 25 °C and water condenses back to liquid. The value measured directly in a bomb calorimeter. Used by US energy agencies and chemists.

LHV (Lower Heating Value, net): heat released minus the latent heat needed to evaporate the product water. The practical value when water exits as vapor in exhaust. Used by European energy agencies (IEA) and mechanical engineers calculating engine/boiler efficiency.

The gap depends on the fuel's hydrogen content: hydrogen has 18% gap (HHV/LHV = 1.18); methane 11%; gasoline 8%; pure carbon 0% (no water produced).

What's the formula for converting LHV to HHV?
HHV = LHV + (nwater / nfuel) × Mwater × ΔHvap(water), where the right-hand term is in kJ per mole of fuel. M_water = 0.018015 kg/mol, ΔH_vap = 2257 kJ/kg at 25 °C (= 40.66 kJ/mol). For methane (n_water/n_fuel = 2): added energy = 2 × 0.018015 × 2257 = 81.3 kJ/mol fuel = 81.3/16.04 = 5.07 kJ/g — exactly the HHV − LHV gap of 55 − 50 = 5 kJ/g. ✓
Which one should I use for engine or boiler efficiency?
Almost always LHV. Engines and boilers exhaust water as vapor (it doesn't condense in the engine), so the latent heat is genuinely lost. A 35% efficient diesel engine on LHV basis is only 33% on HHV basis — the same physical machine, different conventions. The ONLY exception is condensing boilers and condensing furnaces (HVAC), which actively cool exhaust below the dew point to recover the latent heat — those report HHV efficiency (~90-95%) and capture the gap.
Why does hydrogen have such a large HHV/LHV gap?
Because hydrogen produces only water — no CO₂, no other products. Every mole of H₂ produces exactly 1 mole of water (2 H₂ + O₂ → 2 H₂O), and that water represents a huge fraction of the combustion energy. ΔH_vap of water (40.66 kJ/mol) is a sizable fraction of the LHV per mole H₂ (242 kJ/mol), giving a 17% gap. By contrast, methane produces water plus CO₂ (which doesn't condense), so water is a smaller fraction of the energy budget — giving only 11% gap. Pure carbon produces only CO₂ → 0% gap.
Which countries use HHV vs LHV?
HHV (gross) convention: United States (EIA, DOE, EPA), Canada, Mexico — including residential natural-gas billing in therms.
LHV (net) convention: Most of Europe, Asia, Australia — including the IEA (International Energy Agency), most national energy statistics, and engine-efficiency reporting worldwide.
When comparing US energy data with international data, ALWAYS check which convention is used. Cross-border carbon intensity numbers can differ by 5-15% solely from the HHV/LHV choice.
How is heat of combustion measured experimentally?
By bomb calorimetry (ISO 1928, ASTM D240, ASTM D4809). A precisely weighed fuel sample is placed in a sealed steel "bomb" filled with pure O₂ at high pressure (~30 atm), submerged in a water bath of known mass and temperature. The sample is electrically ignited; complete combustion releases heat that warms the surrounding water by a measured ΔT. The calorimeter is calibrated with a known standard (benzoic acid). The result is the HHV directly, because water condenses inside the bomb. LHV is then computed from HHV using the same formula our calculator uses.
What's a typical ΔH_vap value to use?
2257 kJ/kg (= 40.66 kJ/mol) at 100 °C (the boiling point of water at 1 atm) — this is the standard latent heat used in most engineering tables. The calculator's default. Alternative values: 2442 kJ/kg at 25 °C (the IUPAC standard temperature for thermodynamics) — use this for high-precision Hess's Law calculations. The choice affects the HHV − LHV gap by about 8% (2442 vs 2257), which is significant for hydrogen but negligible for high-carbon fuels.
Where do n_water and n_fuel come from?
From the balanced combustion equation. For complete combustion of any hydrocarbon CxHy: CxHy + (x + y/4) O₂ → x CO₂ + (y/2) H₂O. So n_water/n_fuel = y/2. Methane (CH₄, y=4): 2. Propane (C₃H₈, y=8): 4. Octane (C₈H₁₈, y=18): 9. Hydrogen (H₂): 1. For mixtures (natural gas, kerosene, diesel) use a representative average formula; the calculator's presets pre-load typical values.
How does HHV relate to ΔH_combustion in chemistry textbooks?
HHV = −ΔHcombustion° (with sign change). Thermochemistry tables list ΔH_c° as a negative number (combustion releases heat, so ΔH < 0); HHV is the magnitude. For methane: ΔH_c° = −890 kJ/mol = −55.5 MJ/kg → HHV = 55.5 MJ/kg. For octane: ΔH_c° = −5470 kJ/mol = −47.9 MJ/kg → HHV = 47.9 MJ/kg. The standard convention is products at 25 °C with water as liquid — exactly the HHV definition.
Why do condensing furnaces have higher efficiency than conventional ones?
Because they capture the HHV-LHV gap. A conventional natural-gas furnace exhausts water as vapor at 150-200 °C — the LHV efficiency is around 80%, but on HHV basis only 72% (since 11% of the energy left as latent heat). A modern condensing furnace cools the exhaust below the dew point (~55 °C), condenses the water, and recovers the 5.5 MJ/kg latent heat. This pushes the HHV efficiency to 90-95% — closing the 11% gap. The trade-off: condensing units need stainless-steel exhaust (acid condensate) and a drain. Same physics underlies condensing boilers in district heating and cogeneration plants.

Author Spotlight

The ToolsACE Team - ToolsACE.io Team

The ToolsACE Team

Our chemistry tools team implements the universal HHV ↔ LHV relationship that every combustion engineer, thermochemist, and energy analyst needs: HHV (higher / gross heating value) = LHV (lower / net heating value) + the heat released when product water vapor condenses back to liquid. The calculator handles 10 standard fuel presets — hydrogen (the gravimetric champion at 120 MJ/kg), methane, ethane, propane, butane, pentane, paraffin wax, kerosene, diesel, and natural gas — each with CRC-Handbook LHV values, molar mass, and the stoichiometric n_water/n_fuel ratio for complete combustion auto-loaded. Custom mode lets you enter any fuel. Four energy-per-mass units (kJ/g, MJ/kg, kcal/g, BTU/lb), four heat-of-vaporization units, and three mole units cover all engineering and chemistry conventions. Output includes HHV per mole and per gram of fuel, the HHV/LHV ratio, the contribution of water condensation to the total energy, and the total energy released for your specific n_fuel of fuel burned.

Combustion ThermochemistryEnergy EngineeringSoftware Engineering Team

Disclaimer

LHV preset values come from CRC Handbook standard tables at 25 °C and 1 atm; real fuel LHV varies with composition (gasoline 42-46 MJ/kg by octane and additives; natural gas 45-50 MJ/kg by ethane/propane content). Default ΔH_vap = 2257 kJ/kg is at 100 °C; use 2442 at 25 °C for thermodynamics tables. Calculator assumes complete combustion to CO₂ + H₂O — incomplete combustion (CO, soot) gives lower experimental values. HHV/LHV ratios depend on H/C ratio: hydrogen ~1.18, paraffin ~1.07, pure carbon = 1.00.