Problematika mereni velkych prutoku zemniho plynu ve vysokotlakych plynovodech

The thesis submitted refers to the stud of the accuracy connected with the measurement of large amounts of natural gas. It describes the influence of physical property uncertainty on the orifoce plate meter system and the advantage of accurate calculation methods applied in the gas industry. General rules for the calculation of measurement of flow-rate uncertainty are done on the basis of International Standard ISO 5167. In addiction to the near future possibility of the importation of natural gas from Norway to the Czech Republic, the main emphasis insists on the methods for calculation of the compressibility factor, the isentropic exponent and dynamic viscosity, which occur in the basic volume flow-rate formulae. The comparison of computation results with experimental data of seven methods for the compressibility factor calculations are provided. From the classical equations of state the Soave-Redlich-Kwong and Bennedict-Webb-Rubin methods were employed there. Furthermore, the first method constructed for natural gases AGA NX-19, in the Czech Republic still applied its modified version (AGA NX-19mod.) were used to do. At the end the three methods (AGA8 DC-92, SGERG-88 and MGERG-88) which represent today's state of the art were also selected. For the calculation of the isentropic exponent there are comparisons of these eight methods: Soave-Redlich-Kwong, Bennedict-Webb-Rubin, MGERG-88, AGA8-DC92, three empirical equations and the ratio of ideal molar heat capacities. The calculation of the dynamic viscosity is provided in three steps: the low pressure gas viscosity, the gas mixture viscosity at low pressures and the viscosity at high pressures. The computation results of thirty-seven combinations of methods are compared with experimental data. The new methods (especially AGA8-DC92 and SGERG-88) allow the accurate calculation of the compressibility factor with relative percentage difference between calculated and experimental magnitudes of less than 0,1% for wider ranges of natural gas compositions and pressure and temperature fields. The Accuracy within 0,05% for common Norwegian and Russian natural gases for the current high-presure pipeline flow-rate measurement conditions can be achieved. The isentropic exponent can be calculated by the AGA8-DC92 method with uncertainty of less than 0,5%. The calculation of the dynamic viscosity of natural gases seems to be more problematic. The mentioned methods allow the calculation with a relative percentage difference less than 1%Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi