What is the relationship between the higher and lower calorific value of a fuel?
The [GLOSS]calorific value[/GLOSS] of a fuel may be expressed either as the Higher (HCV) or Lower Calorific Value (LCV). The terms “Higher” and “Lower” have various synonyms. These can be for example:
- Upper and Lower Calorific Value
- Gross (GCV) and Net Calorific Value (NCV)
The words Heating Value can be used instead of Calorific Value.
But they all represent the same basic concepts. That is to say a calorific value that is conveniently measurable (HCV) and one, which in most cases represents the reality for available heat for boilers and industrial furnaces.
The higher and lower calorific values of a fuel are related by the following expression:
- QL = Lower Calorific Value (kJ/kg)
- QH = Higher Calorific Value (kJ/kg)
- W = wt% moisture in fuel/100
- H = wt% hydrogen in fuel/100
Alternatively, using units of Btu/lb for the calorific value, the expression can be written as:
In Europe it is usual to normal to use the lower heating value for boiler combustion calculations, whilst in the USA the higher heating value is
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29th October 2001