Heating Value

The gross (high) and net (low) heating values

The heating value is

• the amount of heat produced by combustion of a unit quantity of a fuel

We differentiate in gross and net heating values:

Gross (or high, upper) Heating Value

The gross or high heating value is the amount of heat produced by the complete combustion of a unit quantity of fuel.

The gross heating value is obtained when

• all products of the combustion are cooled down to the temperature before the combustion
• the water vapor formed during combustion is condensed

Net (or lower) Heating Value

The net or lower heating value is obtained by

• subtracting the latent heat of vaporization of the water vapor formed by the combustion

from the gross or higher heating value.

Common Units

Common units used for heating value are

• 1 Btu/lb = 2,326.1 J/kg = 0.55556 kcal/kg
• 1 J/kg = 0.00043 Btu/lb = 2.39x10^-4 kcal/kg
• 1 kcal/kg = 1.80 Btu/lb = 4,187 J/kg

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