Thermal behaviour modelling of a reference calorimeter for natural gas

The French National Metrology and Testing Institute (LNE) build an isoperibolic reference gas calorimeter to measure the calorific value of natural gas with a high level of accuracy with the collaboration of the R&D Division of GDF-Suez. With 3D numerical modelling tools, GDF-Suez developed a comprehensive and refined model of the complete calorimeter geometry and evaluated the heat flux sources to reproduce the thermal behaviour of this calorimeter. The objectives are to optimise the thermal homogeneity and to maximize heat transfer to the water bath. The accurate assessment of the different thermal fluxes transferred to the water bath was performed based on a complete simulation of the combustion of the fuel gas in the burner. The numerical model results fit quite closely the experimental thermal behaviour of the calorimeter. The energy balance shows that approximately 90% of the total energy is absorbed by the water bath and about 10% by the calorimetric walls with a weak contribution of the radiative heat transfer to the calorimeter vessel. A comparative study between the numerical and experimental results confirms both that the geometries of the calorimeter vessels and the glass burner are adequate. The new refined geometric model validates also the location of the thermal sensor in the bath. The expected outcome of both experiments and thermal modelling is to decrease the uncertainty of the calorific value measured with this standard combustion calorimeter.

► Comprehensive and refined 3D model of the geometry of a reference calorimeter.
► Evaluation of heat flux sources to reproduce thermal behaviour of the water bath.
► Integration of a complete simulation of the combustion in the burner.
► 90% of the total energy is absorbed by the water bath.
► Comparison between modelling and experiments confirms the geometries of the set up.