Heat of Combustion Calculator

This heat of combustion calculator will tell you the heat released during the combustion process. When fuel burns or undergoes the combustion process, it combines with oxygen in the air and forms carbon dioxide and water vapor along with some heat. The heat of combustion, also known as the higher heating value, is a function of the number of moles of water vapor formed and considering the heat of vaporization.

The heat of combustion is a crucial parameter in the area of energy and heat used to drive machines like internal combustion engines, fuel cells, waste heat recovery to reuse it. It is also used to estimate the quality of fuels like natural gas or coal. Read on to understand if you are wondering what higher heating value is or how to calculate the heat of combustion?

Learn more about engines in the horsepower calculator.

Definition of the heat of combustion is the amount of energy released when a particular fuel undergoes combustion. The heat of combustion goes by several names like higher heating value, higher calorific value, and upper heating value. When fuel is combusted, one of the byproducts is water vapor that is formed due to heat of vaporization and is often wasted when allowed to escape. However, in the formula for the heat of combustion, the energy to form water vapor is considered. The heat of combustion having a symbol, $H_c$ is given by the equation:

where:

• $LHV$ – Lower heating value;
• $H_v$ – Heat of vaporization;
• $n_{H_2O}$ – Number of moles of water $(\text{H}_2\text{O})$ released; and
• $n_{fuel}$ – Number of moles of fuel combusted.

Heat of vaporization definition: the amount of energy required to transform the liquid into gas form.

The lower heating value is the energy produced from the combustion of fuel, considering water vapor loss. In other words, lower heating value is the difference between higher heating value and heat of vaporization of water vapor. The heat of combustion, lower heating value, and heat of vaporization are measured in the units of energy per mass, i.e., kJ/kg or BTU/lb.

Now let's have a look at the steps for calculating the higher heating value:

1. Enter the lower heating value of the fuel.
2. Insert the heat of vaporization of water of the fuel.
3. Fill in the number of moles of water vaporized.
4. Enter the number of moles of fuel combusted.
5. The calculator uses the heat of the combustion equation to return its value.

Determine the heat of combustion of methane given its lower heating value is 50 MJ/kg and it releases 5 moles of water vapor when 2 moles of fuel is combusted

1. Select Methane from the list of fuels.
2. The heat of vaporization for water as 2.257 MJ/kg.
3. Fill in the number of moles of water vaporized as 5.
4. Enter the number of moles of fuel combusted as 2.
5. Using the heat of combustion formula:

Before you go, check your engine's capacity with our engine displacement calculator.