ISO 20765-2:2015 pdf free

ISO 20765-2:2015 pdf free.Natural gas一Calculation of thermodynamic properties
The method described here is also applicable with no increase in uncertainty to wider ranges of temperature, pressure, and composition for which the method of Part 1 is not applicable. For example, it is applicable to natural gases with lower content of methane [down to 0,30 mole fraction), higher content of nitrogen (up to 0,55 mole fraction), carbon dioxide (up to 0,30 mole fraction), ethane (up to 0,25 mole fraction), and propane (up to 0,14 mole fraction), and to hydrogen-rich natural gases. A practical usage is the calculation of properties of highly concentrated CO2 mixtures found in carbon dioxide sequestration applications.
The mixture model presented here is valid by design over the entire fluid region. In the liquid and dense-fluid regions the paucity of high quality test data does not in general allow definitive statements of uncertainty for all sorts of multi-component natural gas mixtures. For saturated liquid densities of LNG-type fluids in the temperature range from 100 Kto 140 K (-280 °F to -208 °F), the uncertainty is ≤(0,1 – 0,3) %, which is in agreement with the estimated experimental uncertainty of available test data.
The model represents experimental data for compressed liquid densities of various binary mixtures to within +(0,1 – 0,2) % at pressures up to 40 MPa (5800 psia), which is also in agreement with the estimated experimental uncertainty. Due to the high accuracy of the equations developed for the binary subsystems, the mixture model can predict the thermodynamic properties for the liquid and dense-fluid regions with the best accuracy presently possible for multi-component natural gas fluids.
pressure at which an infinitesimal amount of liquid is in equilibrium with a bulk vapour for a specified temperature
Note 1 to entry: More than one dew pressure may exist at the specified temperature. For example, isothermal compression at 300 K with a gas similar to that shown in Figure 1: At low pressure the mixture is a gas. At just above 2 MPa (the dew pressure), a liquid phase initially forms. As pressure increases more liquid forms in the two-phase region, but a further increase in pressure reduces the amount of liquid (retrograde condensation) until at about 8 MPa where the liquid phase disappears at the upper dew pressure, and the mixture is in the dense gas phase. In the two-phase region, the overall composition is as specified, however the coexisting vapour and liquid will have different compositions.ISO 20765-2 pdf free.