Measurements of the Calorific Value of Methane with the New GERG Reference Calorimeter

A new reference calorimeter has been developed under a European research project and set-up by Physikalisch-Technische Bundesanstalt (PTB) in Germany. The objective of the project is to measure the superior calorific value (SCV) of methane and other pure gases with a measurement uncertainty of less than 0.05 %. This paper presents the measurement results obtained for methane. Nine repeatability measurements were made. The molar SCV obtained when the measurements were averaged is 890.578 kJ·mol^-1. This value agrees very accurately with the value of 890.63 kJ·mol^-1 specified by ISO 6976 [ Natural Gas—Calculation of Calorific Values, Density, Relative Density and Wobbe Index from Composition. International Standard ISO 6976, corrected and reprinted 1996-02-01]. Twice the standard deviation determined for the measurements is 0.023 % and is thus clearly lower than in previous experiments. Two independent uncertainty analyses confirm that the envisaged total uncertainty of 0.05 % is achieved (95 % confidence level).