J. E. Powers

A new high-pressure recycle-flow calorimeter and results of determinations with ethane

A new recycle-flow calorimeter is described with which the thermodynamic properties of fluids can be determined between pressures of 2 to 20 MPa and temperatures of 90 to 400 K. Precise control of both flowrate and pressure is provided by dual precision metering pumps. Details are presented on a new calorimeter which incorporates several innovations. Heat losses from this calorimeter are reduced by a novel shielding arrangement and were shown to be less than the experimental precision of i 0.1 per cent. The calorimeter can be operated in either the isobaric or the throttling mode. The results of experimental determinations around the critical point of ethane are described. Enthalpies of vaporization and heat capacities were obtained by operating in the isobaric mode. Determinations in the throttling mode yielded isothermal throttling coefficients and Joule-Thomson coefficients. Analysis of these results showed that the thermodynamic consistency of the enthalpies in the isobaric and isothermal mode is better than 0.1 per cent, and that of the derived values of properties is 0.4 per cent or better.

Experimental determination of the enthalpy of mixing of N + CO2 under pressure

A once-through flow-calorimetric facility for measuring the enthalpy of mixing of binary gas mixtures at elevated pressures is described. The design of a new flow calorimetric incorporated in the facility is presented. Results for N 2 + CO 2 from mole fraction of nitrogen 0.22 to 0.73 are reported at the nominal conditions 40°C: 34.02 and 64.64 atm, and 31°C: 34.02 and 64.64 atm. The experimental results are interpreted and smoothed, and compared with predictions using the Benedict-Webb-Rubin equation of state. The probable accuracy of the results is discussed, along with a check on the assumption of adiabaticity in the calorimeter.

Direct determinations of the effect of pressure on the enthalpy of nitrogen

The isothermal throttling (Eucken) coefficient ϕ of nitrogen has been measured in a new apparatus. Measurements were made at 173.7, 273.5, and 367.2° K at pressures from 7 to 135 atm. The results are compared with other direct measurements, with Joule-Thomson data, and with pressure-volume-temperature data.