William M. Haynes

Isochoric (p, Vm, T) measurements on CO2 and on (0.982CO2 + 0.018N2) from 250 to 330 K at pressures to 35 MPa☆☆☆

Abstract Comprehensive isochoric ( p , V m , T ) measurements have been performed for pure CO 2 and for (0.982CO 2 + 0.018N 2 ). The range of state points studied for pure CO 2 include those with amount-of-substance densities from 1 to 24 mol·dm −3 , temperatures from 250 to 330 K, and pressures to 34 MPa. Similarly, the mixture was studied over amount-of-substance densities of 1 to 24 mol·dm −3 , temperatures from 250 to 330 K, and pressures to 33 MPa. Based on these and other experimental results from the literature, a 32-term equation of state of the form suggested by Jacobsen and Stewart has been developed for pure CO 2 . This equation was then used to demonstrate the effect of a small amount of N 2 on the ( p , V m , T ) surface of CO 2 —an effect which can be as great as 100 per cent in the amount-of-substance density at fixed temperature and pressure. Finally, the equation of state for pure CO 2 was used in a conformal-solution model to calculate the mixture amount-of-substance densities which had been obtained in this study. In general the results of this calculation were very good—the model reproduced the experimental results to within an r.m.s. deviation of 0.26 per cent.

Measurements of the orthobaric liquid densities of methane, ethane, propane, isobutane, and normal butane☆

Abstract The orthobaric liquid densities of the major components of natural gas have been determined with a magnetic suspension densimeter. This paper reports results for methane (105 to 160 K), ethane (100 to 270 K), propane (100 to 288 K), isobutane (115 to 300 K), and normal butane (135 to 300 K). The imprecision of the measured densities is approximately 0.015 per cent; the estimated overall uncertainty is 0.1 per cent at low temperatures and decreases to 0.06 per cent at 300 K. A simple expression has been used to represent the densities as a function of temperature. Comprehensive comparisons with the experimental results of other investigators are presented.

Orthobaric liquid densities and excess volumes for binary mixtures of low molarmass alkanes and nitrogen between 105 and 140 K

Abstract A magnetic suspension densimeter has been used to determine orthobaric liquid densities of gravimetrically prepared binary mixtures of the major components of liquefied natural gas (LNG) i.e. nitrogen, methane, ethane, propane, i-butane, and n-butane, generally between 105 and 140 K. All binary combinations were included in this study, with the exception of nitrogen + i-butane and nitrogen + n-butane. Uncertainties in the reported liquid-mixture densities are discussed in detail. Comparisons are made between excess volumes computed from the present results and comparable values from the literature. It was found that the volumetric properties of binary liquid mixtures of the heavy hydrocarbons (those mixtures not containing nitrogen or methane) are closely approximated by ideal mixing. Some observations are included on the use of excess volumes of the heavy hydrocarbon systems to determine effective molar volumes of n-butane in liquid mixtures below its triple-point temperature. For mixtures containing nitrogen or methane, approximate total vapor pressures are given.

Isochoric (p, Vm, x, T) measurements on (methane + ethane) from 100 to 320 K at pressures to 35 MPa☆

Abstract Comprehensive isochoric (p, Vm, x, T) values have been obtained for {xCH4 + (1 − x)C2H6} with x = 0.35, 0.50, and 0.69 at amount-of-substance densities from 1 to 25 mol·dm−3. The measurements for each composition cover a temperature range from approximately 100 to 320 K at pressures up to 35 MPa. For each mixture the results have been fit to a 32-term modified Benedict-Webb-Rubin equation of state. Further development of the extended corresponding-states model has been accomplished using the results presented here. Comparisons with values from independent sources have been made where possible.

Measurements of orthobaric-liquid densities of multicomponent mixtures of lng components (N2, CH4, C2H6, C3H8, CH3CH(CH3)CH3, C4H10, CH3CH(CH3)C2H5, and C5H12) between 110 and 130 K☆

Abstract A magnetic suspension densimeter has been used to measure the orthobaric-liquid densities of 17 multicomponent mixtures of the major components of liquefied natural gas ( lng ) at temperatures from 110 to 130 K. These mixtures ranged from a ternary mixture containing nitrogen, methane, and butane to 4-to-8-component methane-rich (74 to 90 moles per cent) mixtures containing up to 5 moles per cent of nitrogen, 16 moles per cent of ethane, 7 moles per cent of propane, 5 moles per cent of the butanes, and 0.44 mole per cent of the pentanes. Some of the compositions were selected to simulate commercial lng mixtures. Results of vaporpressure measurements are also presented. The major purpose of this work was to obtain multicomponent-mixture values that could be used to test mathematical models that have been developed for the prediction of lng densities. To demonstrate the consistency of the multicomponent-mixture values, comparisons are presented between experimental densities and calculated values from an extended corresponding-states method that was optimized to purefluid and binary-mixture results from the lng density project here. The total uncertainty of a single density measurement is estimated to be approximately 0.1 per cent, which includes an allowance of three times the standard deviation for random error. The imprecision of measurement is a few parts in 104.

Orthobaric liquid densities and excess volumes for multicomponent mixtures of low molar-mass alkanes and nitrogen between 105 and 125 K☆

Abstract A magnetic suspension densimeter has been used to determine orthobaric liquid densities of gravimetrically prepared multicomponent mixtures containing the major components of liquefied natural gas, i.e. nitrogen, methane, ethane, propane, isobutane, and normal butane, between 105 and 125 K. These results were obtained to provide a test of the capability of mathermatical models to predict the densities of liquefied natural-gas mixtures. Combinations of the subject components were chosen to provide the most severe test of the models and the possibility of using the measured densities to optimize parameters of the models. Deviations are given between the experimental densities for each mixture and values predicted with an extended corresponding-states model optimized to binary-mixture and pure-component orthobaric liquid densities obtained with the same apparatus. Uncertainties of the present results are discussed in relation to the experimental technique, the knowledge of the compositions of the liquid mixtures, and the comparisons between the experimental and predicted results. Approximate total vapor pressures are also given for each mixture at the temperatures studied.

Orthobaric liquid densities and dielectric constants of (methane+2-methyl-propane) and (methane+n-butane) at low temperatures☆

Abstract Measurements of the orthobaric liquid densities and dielectric constants of methane-rich (methane+2-methylpropane) and (methane+n-butane) have been obtained at temperatures between 110 and 140 K. Densities were determined with a magnetic-suspension densimeter, while a concentric-cylinder capacitor was used for simultaneous measurements of dielectric constant. These measurements were part of an experimental program that has provided a consistent and comprehensive set of densities for the major components of liquefied natural gas (LNG) and their mixtures, which was used to develop mathematical models for the calculation or prediction of LNG densities. Along with the (methane+2-methylpropane) and (methane+n-butane) experimental densities and dielectric constants, are presented experimental vapor pressures, as well as excess volumes, Clausius-Mossotti functions, and excess Clausius-Mossotti functions, derived from the densities and dielectric constants. Comparisons are shown between the excess volumes of the present work and those from independent measurement using an extended corresponding-states model that had been optimized to the results from this work. The total uncertainty of a single density measurement is approximately 0.1 per cent with a precision of a few parts in 104. Dielectric constants are estimated to be accurate to approximately 0.05 per cent. A brief description of the apparatus, experimental method, and procedures is also presented.

Guidelines for reporting of phase equilibrium measurements (IUPAC Recommendations 2012)

Recommendations are given for reporting in the primary scientific literature of measurements involving phase equilibrium. The focus is on documentation issues, and many of the recommendations may also be applied to the more general fields of thermodynamic and transport properties. The historical context of the work and specific plans for implementation of the recommendations are discussed.

Low-density isochoric (p, V, T) measurements on (nitrogen + methane)

Abstract Isochoric (p, V, T) measurements have been made on three mixtures of nitrogen and methane (0.29N2 + 0.71CH4), (0.50N2 + 0.50CH4), and (0.68N2 + 0.32CH4) at densities of 1 to 6 mol·dm−3. The three isochores for each mixture cover a temperature range from approximately 150 to 320 K up to a maximum pressure of 16 MPa. Comparisons with other experimental results and with values calculated from an extended corresponding-states model are discussed.

Isochoric heat capacity measurements for binary refrigerant mixtures containing difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), and trifluoroethane (R143a) from 200 to 345 K at pressures to 35 MPa

Molar heat capacities at constant volume Cv were measured for binary refrigerant mixtures with an adiabatic calorimeter with gravimetric determinations of the amount of substance. Temperatures ranged from 200 to 345 K, while pressures extended up to 35 MPa. Measurements were conducted on liquid samples with equimolar compositions for the following binary systems: R32/R134a, R32/R125, R125/R134a, and R125/R143a. The uncertainty is 0.002 K for the temperature rise and is 0.2% for the change-of-volume work, which is the principal source of uncertainty. The expanded relative uncertainty (with a coverage factor k=2 and thus a two-standard deviation estimate) for Cv is estimated to be 0.7%.