The heat liberated by the combustion of a unit quantity of a fuel under specific conditions; it is measured in calories. During combustion, water vapor is produced and it is possible to recover the heat contained in this water vapor by condensing it.
The higher calorific value (or gross calorific value, GCV) supposes that the water of combustion is entirely condensed and that the heat contained in the water vapor is recovered. The lower calorific value (or net calorific value, NCV) supposes that the products of combustion contains the water vapor and that the heat in the water vapor is not recovered. Conventionally, the basic calorific value for solid and liquid fuels is the gross calorific value at constant volume, and for gaseous fuels it is the gross calorific value at constant pressure.
Related category• HEATING
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