By using an isothermal throttling calorimeter, built for recirculating vapor operation, the effects of pressure on the enthalpy of methane and two methane-propane (93.9 and 86.2% methane) mixtures were measured. Pure methane was run at 150°F. and the two mixtures were studied at 90, 150, and 200°F. The pressures for these experiments were 500, 1,000, 1,500, and 2,000 lb./sq.in.abs.
The resulting data were compared with similar data from other sources for these same systems and conditions. Agreement is good with enthalpy values obtained from both experimental volumetric and Joule-Thomson data.
Prediction methods for the isothermal pressure effect on the enthalpy are compared with these data. These methods demonstrate the reliability of the Redlich-Kwong and Benedict-Webb-Rubin equations and Pitzer's corresponding states correlation for calculating isothermal enthalpy changes for these systems and conditions.