Thermodynamic Properties of Propane. II. Molar Heat Capacity at Constant Volume from (85 to 345) K with Pressures to 35 MPa

Abstract

Molar heat capacities at constant volume (C V) were measured with an adiabatic calorimeter for pure propane. The high purity of the samples was verified by chemical analysis. Temperatures ranged from the triple point of propane near 85 K to the upper temperature limit of the calorimeter at 345 K, while pressures ranged up to 35 MPa. Measurements were conducted on liquid propane in equilibrium with its vapor and on compressed liquid samples along isochores. Heat capacity results are reported for two-phase (C V (2)), saturated liquid (C σ), and single-phase (C V) isochores. Vapor pressure data are based on measurements of C V (2) along a two-phase isochore. Measurements were also made to determine the triple-point temperature of (85.525 ± 0.005) K and heat of fusion of (3508 ± 20) J·mol−1 for propane near its triple point. The principal sources of uncertainty in C V are the temperature-rise measurement and the change-of-volume work adjustment. The expanded uncertainty (i.e., a coverage factor k = 2 and thus a two-standard deviation estimate) for values of C V (2) is estimated to be 0.5 %; for both C σ and C V, it is 0.7 %.

Molar Heat Capacity at Constant Volume for Isobutane at Temperatures from (114 to 345) K and at Pressures to 35 MPa

“…6 The calorimeter consists of a nearly adiabatic cell (also called a calorimetric bomb) that is spherical and has been operated at temperatures from (14 to 345) K at pressures up to 35 MPa. During a measurement, a sample of well-established mass is confined within the cell with a well-known volume (approximately 77 cm 3 ); as shown by Magee 6 and Perkins et al, 8 the exact volume varies with both temperature and pressure. After a precisely measured quantity of electrical energy (Q) pulse is applied and the cell temperature equilibrates, the resulting temperature increase (∆T ) T 1 -T 2 ) is measured.…”

Thermodynamic Properties of Propane. IV. Speed of Sound in the Liquid and Supercritical Regions

“…This paper is the fourth paper in a series of papers on the thermodynamic properties of propane. The first two papers describe measurements of the p –ρ– T behavior and isochoric heat capacity of propane carried out at the National Institute of Standard and Technology in Boulder. , In parallel with this work, a new fundamental equation of state for propane was developed by Lemmon et al, which is presented in the third paper of the series. In the optimization process of this equation of state, our speed of sound data were already used as part of the experimental data set, to which the equation of state was fitted.…”

Isobaric Heat Capacity Measurements of Liquid Methane, Ethane, and Propane by Differential Scanning Calorimetry at High Pressures and Low Temperatures

“…However, this seems optimistic given the offset of the EOS from the adiabatic calorimetry data of Perkins et al as well as the distribution of deviations of the literature data from the EOS. The c v data of Perkins et al, with a stated uncertainty of 0.005· c v , were converted to c p using: c p = c v + v T α 2 κ T Here the specific volume, v , coefficient of thermal expansion, α, and isothermal compressibility, κ T , were calculated using the EOS of Lemmon et al The mean and maximum deviations of the c p derived from Perkins et al from the EOS of Lemmon et al are (0.08 and 0.016)· c p in the temperature range of (80 to 280) K. This is consistent with the mean and maximum deviations of our data from this EOS which are (0.009 and 0.017)· c p , respectively. Additionally, the saturated liquid heat capacity, c σ , data of Goodwin and Guigo et al were converted to c p data using: c p = c σ + v T α γ σ Here γ σ is the slope of the vapor pressure curve, (∂ p /∂ T ) σ , and v , α, and γ σ were calculated using the EOS of Lemmon et al The mean deviation of the Goodwin data from the EOS of Lemmon et al was only 0.003· c p .…”

“…Lemmon et al estimate that their EOS calculates c p to an uncertainty of 0.005· c p . However, this seems optimistic given the offset of the EOS from the adiabatic calorimetry data of Perkins et al as well as the distribution of deviations of the literature data from the EOS. The c v data of Perkins et al, with a stated uncertainty of 0.005· c v , were converted to c p using: c p = c v + v T α 2 κ T Here the specific volume, v , coefficient of thermal expansion, α, and isothermal compressibility, κ T , were calculated using the EOS of Lemmon et al The mean and maximum deviations of the c p derived from Perkins et al from the EOS of Lemmon et al are (0.08 and 0.016)· c p in the temperature range of (80 to 280) K. This is consistent with the mean and maximum deviations of our data from this EOS which are (0.009 and 0.017)· c p , respectively.…”

“…Relative deviations of the isobaric heat capacity of propane, c p , from the reference equation of state (Lemmon et al) heat capacity, c p ,ref . ■, this work at 5.3 MPa; ◆, this work at 5.2 MPa; ●, this work at 3.7 MPa; ▲, this work at 1.1 MPa; ×, Kemp and Egan; □, Guigo et al; ○, Goodwin;◇, Lammers et al; △, van Kasteren and Zeldenrust; +, Perkins et al (Note the data Guigo et al and Goodwin were converted from c σ to c p using specific volumes, coefficieints of thermal expansion, and slope of the vapor pressure curve calculated using the Lemmon et al equation of state implemented in REFPROP 9.0. Additionally, the data of Perkins et al were converted from c v to c p using specific volumes, coefficients of thermal expansion, and isothermal compressibilities calculated using the Lemmon et al equation of state implemented in REFPROP 9.0.…”