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How do we measure calorific value?

One of the key quality aspects of a fuel is the Calorific Value (CV), in effect the amount of potential energy the fuel contains which can become available, upon combustion, as heat. This is known as the calorific value or CV.

Two values are normally quoted; the Gross (higher) and the Net (lower) CV, which we must measure to determine the potential output. So, how do we measure calorific value?

Calorific ValueMeasurement of Calorific Value

To measure calorific value, we use a calorimeter. The fuel is first combusted with Oxygen, under pressure, in a sealed “bomb”. Then, the heat of the subsequent reaction is measured from the temperature rise of a surrounding water bath.

By calibration of the calorimeter system with, for example, thermochemical grade Benzoic Acid, the Gross Calorific value at constant volume is determined.

Additional analytical parameters such as the Sulphur content and the heat of formation of acids also need to be determined to compute this value accurately. We obtain this analysis at constant volume, as it’s combusted in a fixed volume “bomb”, though it’s usual to express the result at constant pressure.

The gross calorific value may be thought of as the maximum potential internal energy content of the fuel and can be expressed on a constant pressure or constant volume basis.

Testing your solid fuels

Alfred H Knight Energy Services are suitably experienced and equipped to perform Calorific Value testing on all types of biomass, solid recovered fuels and refuse derived fuels. Our lab technicians are experts in the testing and inspection of alternative fuels and operate in a timely manner.

We are UKAS accredited to ISO17025 for several calorimetric standards, including BS ISO 1928, BS EN ISO 18125, BS EN 15400 and ASTM D5865.

For further information, or if you wish to discuss your testing requirements, please head to our contact page.