Heat of combustion

The calorific value Hs (deprecated calorific calorific value or gross calorific value Ho) is a measure of the specific per unit of assessment contained in a fabric thermal energy. The calorific value is identical to the absolute value of the specified standard enthalpy with negative sign ΔVH ° of the general thermodynamics.

The calorific value of fuel is the amount of heat that is released upon combustion and subsequent cooling of the flue gases to 25 ° C and its condensation.

The calorific value takes into consideration both the energy required for heating the combustion air and the exhaust gases and the heat of condensation and evaporation of liquids, especially water. In contrast, the calorific value (formerly "lower heating value " ) refers to the amount of heat to the initial temperature of the combustible mixture is released during the combustion and subsequent cooling, the combustion water is still present in vapor form. The calorific value of water-rich fuels is therefore significantly lower than its calorific value and by the amount of the enthalpy of vaporization of the water vapor present.

The physical size

Is specified, the calorific value than the mass-related energy value expressed in kilojoules per ( kg ) program in kJ / g or kJ / kg, as volume-based heating value per liter in kJ / l or per cubic meter in kJ / m³. For the gaseous components referring to the calorific value of volume at 101.325 kPa and 25 ° C ( standard conditions). The information is then in kilojoules per standard cubic meter as kJ / m³ STP, where " iN " " in standard condition" means.

The current formula reads characters Hs or B. The subscript s is "higher" for Latin superior. Ho ( the o stand for the upper calorific value ), kcal ( kilocalorie ) as well kJ / mN ³ with indexed unit are no longer the standard.

Energy and Heating

Each time the combustion process of hydrocarbons (such as natural gas or oil ) is produced by the combination of oxygen and hydrogen from the combustion air from the fuel vapor. The energy contained in the water vapor in the exhaust gas and thus is lost in conventional technology over the hot exhaust gases through the chimney. Modern condensing boiler condenses the water vapor contained in the exhaust gas through a heat exchanger. So that the heat of condensation contained in the exhaust gas is recovered as far as possible.

Norms and Standards

  • EN 437:2003 Test gases - Test Pressures - Appliances categories; German: DIN EN 437:2003-09 Calibration gas mixtures - Test pressures - equipment categories and ÖNORM EN 437:1994-05-01 devices for use with fuel gases - Calibration gas mixtures - Proofs and equipment categories This Euro standard performs well in the sense of international harmonization, the formula Hs sign a
  • DIN 5499 calorific value and heat value terms ( January 1972 )
  • DIN 1343 reference state, standard state, standard volume; Concepts and values ​​( January 1990)
  • DIN 51900 Determination of calorific value by the bomb calorimeter and calculation of net calorific Part 1 Principles, apparatus, methods (April 2000)
  • Part 2 procedure with isoperibolem or static jacket calorimeter (May 2003)
  • Part 3 process with adiabatic jacket ( July 2004)