Speed of Sound Measurements of Binary Mixtures of 1,1,1,2-Tetrafluoroethane (R-134a), 2,3,3,3-Tetrafluoropropene (R-1234yf), and trans-1,3,3,3-Tetrafluoropropene (R-1234ze(E)) Refrigerants.

Speed of sound data measured using a dual-path pulse-echo instrument are reported for binary mixtures of 1,1,1,2-tetrafluoroethane (R-134a), 2,3,3,3-tetrafluoropropene (R-1234yf), and trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)). For each binary mixture, the speed of sound is studied at two compositions of approximately (0.33/0.67) and (0.67/0.33) mole fraction. The conditions covered in this study range in temperature from 230 to 345 K and from pressures slightly above the bubble curve up to a maximum pressure of 51 MPa. However, to avoid potential polymerization reactions, data for mixtures containing R-1234yf are limited to a maximum pressure of 12 MPa at temperatures below 295 K and 8 MPa at temperatures above 295 K. The mean uncertainty of the measured speed of sound is less than 0.1%, where relative combined expanded uncertainties at individual state points range from 0.04 to 0.4% of the measured speed of sound value. The greatest combined expanded uncertainties are encountered as the state point approaches the mixture critical region where weakened echo signals and lower speed of sound values are observed. The reported data are compared to available REFPROP mixture models, which are not adjusted using the data reported here, with average absolute deviations ranging from 0.27 to 0.75% with maximum deviations as high as 1.1%. The comparisons to the REFPROP correlations show that further adjustments to the mixture models are needed to provide a representation of the data within its experimental uncertainty.

Measurement and Correlation of the Thermal Conductivity of 1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone.

New experimental data for the thermal conductivity of 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-pentanone (Novec 649) are reported for vapor, liquid and supercritical states. These new experimental data were obtained with transient hot-wire apparatus over the temperature range from 183 K to 501 K and at pressures from 0.02 MPa to 69 MPa. These data were used to develop a wide-range correlation for the thermal conductivity of the vapor, liquid and supercritical fluid. The experimental data reported here have an uncertainty of 1 % for the liquid and supercritical regions (densities > 600 kg m-3), 1.5 % for vapor and supercritical regions (pressures ≥ 1 MPa and densities < 200 kg m-3), 3 % for supercritical states (200 kg m-3 ≤ densities ≤ 600 kg m-3), and 3 % for vapor and supercritical states (pressures < 1 MPa). The thermal-conductivity correlation developed in this work is estimated to have an expanded relative uncertainty, at a 95 % confidence level, ranging from approximately 1 % to 4 % that depends upon the temperature and pressure, with larger uncertainties in the critical region.

Measurement and Correlation of the Thermal Conductivity of trans-1-Chloro-3,3,3-trifluoropropene (R1233zd(E)).

New experimental data on the thermal conductivity of trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) are reported that allow the development of wide-range correlations. These new experimental data, covering a temperature range of 204 K to 453 K at pressures from 0.1 MPa to 67 MPa, are used to develop a correlation for the thermal conductivity. The experimental data reported here have an uncertainty of (1 - 1.5) % for liquid measurements and for gas at pressures above 1 MPa, increasing to (3 - 4) % for gas at low pressures (less than 1 MPa) and near the gas-liquid critical point. Based on the uncertainty of and comparisons with the present data, the thermal-conductivity correlation for R1233zd(E) is estimated to have a relative expanded uncertainty ranging at a 95 % confidence level from 1 % to 4 % depending on the temperature and pressure, with larger uncertainties in the critical region.

A Dual-Path Pulse-Echo Instrument for Liquid-Phase Speed of Sound and Measurements on p-Xylene and Four Halogenated-Olefin Refrigerants [R1234yf, R1234ze(E), R1233zd(E), and R1336mzz(Z)].

We describe an instrument to measure the speed of sound in liquids based on the dual-path, pulse-echo technique; it covers a temperature range of 228.15-423.15 K, with pressures of up to 93 MPa. It differs from similar instruments in the method of mounting the quartz-crystal transducer, a path-length ratio of 2.5:1, and automated data-collection protocols. The path-length difference was calibrated with measurements on high-purity propane. The performance of the instrument was verified by comparison with recent literature data on p-xylene. We present new liquid-phase measurements for the halogenated-olefin refrigerants 2,3,3,3-tetrafluoroprop-1-ene [R1234yf], trans-1,3,3,3-tetrafluoroprop-1-ene [R1234ze(E)], trans-1-chloro-3,3,3-trifluoroprop-1-ene [R1233zd(E)], and cis-1,1,1,4,4,4-hexafluorobut-2-ene [R1336mzz(Z)]. These measurements cover a combined temperature range of 230 to 420 K, with pressures of up to 50 MPa; these data are compared to literature data (where available) and multiproperty equations of state. The average relative expanded uncertainty in the speed of sound ranged from 0.035 to 0.088% for the different fluids.

Modeling and simulation credibility assessments of whole-body finite element computational models for use in NASA extravehicular activity applications.

Computational finite element (FE) models are used in suited astronaut injury risk assessments; however, these models' verification, validation, and credibility (VV&C) procedures for simulating injuries in altered gravity environments are limited. Our study conducts VV&C assessments of THUMS and Elemance whole-body FE models for predicting suited astronaut injury biomechanics using eight credibility factors, as per NASA-STD-7009A. Credibility factor ordinal scores are assigned by reviewing existing documentation describing VV&C practices, and credibility sufficiency thresholds are assigned based on input from subject matter experts. Our results show the FE models are credible for suited astronaut injury investigation in specific ranges of kinematic and kinetic conditions correlating to highway and contact sports events. Nevertheless, these models are deficient when applied outside these ranges. Several credibility elevation strategies are prescribed to improve models' credibility for the NASA-centric application domain.

Speed of Sound Measurements of Binary Mixtures of Difluoromethane (R-32) with 2,3,3,3-Tetrafluoropropene (R-1234yf) or trans-1,3,3,3-Tetrafluoropropene (R-1234ze(E)) Refrigerants.

Sound speed data measured using a dual-path pulse-echo instrument are reported for binary mixtures of difluoromethane (R-32) with 2,3,3,3-tetrafluoropropene (R-1234yf) or trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)). The sound speed is reported at two compositions for each binary mixture of approximately (0.33/67) and (0.67/0.33) mole fraction at temperatures between 230 K and 345 K. Data are reported from pressures slightly above the bubble point to 12 MPa for R-32/1234yf mixtures to avoid potential polymerization reactions and to 53 MPa for the R-32/1234ze(E) mixtures. The mean uncertainty of the sound speed data are less than 0.1% of the measured value where uncertainties at individual state points range from 0.04% to 0.5% of the measured value as the conditions approach the mixture critical region. The reported data are compared to available Helmholtz-energy-explicit EOS included in REFPROP and all systems studied have average absolute deviations greater than 2%. The comparisons show that further adjustments to the mixture models are needed to provide a reasonable representation of the data within its experimental uncertainty.

Thermal Conductivity of Binary Mixtures of 1,1,1,2-Tetrafluoroethane(R-134a), 2,3,3,3-Tetrafluoropropene (R-1234yf), and trans-1,3,3,3-Tetrafluoropropene (R-1234ze(E)) Refrigerants.

A total of 2160 thermal conductivity data points, measured using a transient hot-wire instrument, are reported for binary mixtures of R-134a, R-1234yf, and R-1234ze(E) refrigerants from 200 to 340 K to pressures of 12 MPa for mixtures containing R-1234yf and to 50 MPa for R-134a/1234ze(E) mixtures. Data are reported at compositions of approximately (0.33/0.67) mole fraction and (0.67/0.33) mole fraction for each binary mixture investigated. The estimated relative expanded uncertainty of the thermal conductivity measurements is less than 2%. The data are used to refit binary interaction parameters for the Extended Corresponding States (ECS) model implemented in REFPROP (version 10.0). Additionally, the data in this study are used to assess the performance of a generalized entropy scaling model for refrigerants. Finally, the strengths and weaknesses of the ECS and entropy scaling models are compared.

Reference Correlation for the Viscosity of Xenon from the Triple Point to 750 K and up to 86 MPa.

A new wide-ranging correlation for the viscosity of xenon, based on the most recent theoretical calculations and critically evaluated experimental data, is presented. The correlation is designed to be used with an existing equation of state, and it is valid from the triple point to 750 K, at pressures up to 86 MPa. The estimated expanded uncertainty (at a coverage factor of k = 2) varies depending on the temperature and pressure, from 0.2 % to 3.6 %. A term accounting for the critical enhancement is also included. The correlation behaves in a physically reasonable manner when extrapolated to 200 MPa, however care should be taken when using the correlations outside of the validated range.

Measurement and Correlation of the Thermal Conductivity of cis-1,1,1,4,4,4-hexafluoro-2-butene.

New experimental data for the thermal conductivity of cis-1,1,1,4,4,4-hexafluoro-2-butene (R-1336mzz(Z)) are reported for vapor, liquid and supercritical states. These data were obtained with transient hot-wire apparatus over the temperature range from 192 K to 498 K and at pressures from 0.05 MPa to 69 MPa. These data were used to develop a wide-range correlation for the thermal conductivity of the vapor, liquid, and supercritical fluid. The experimental data reported here have an uncertainty of 1 % for the liquid and supercritical regions (densities above 600 kg·m-3), 1.5 % for vapor and supercritical regions (pressures greater than or equal to 1 MPa and densities less than 200 kg·m-3), 3 % for supercritical states (densities between 200 kg·m-3 and 600 kg·m-3), and 3 % for vapor and supercritical states (pressures below 1 MPa). The thermal-conductivity correlation developed in this work is estimated to have an expanded relative uncertainty, at a 95 % confidence level, ranging from approximately 1.4 % to 4.2 % depending on the temperature and pressure, with larger uncertainties in the critical region.

Speed-of-Sound Measurements in (Argon + Carbon Dioxide) over the Temperature Range from (275 to 500) K at Pressures up to 8 MPa.

The speed of sound of two (argon + carbon dioxide) mixtures was measured over the temperature range from (275 to 500) K with pressures up to 8 MPa utilizing a spherical acoustic resonator. The compositions of the gravimetrically prepared mixtures were (0.50104 and 0.74981) mole fraction carbon dioxide. The vibrational relaxation of pure carbon dioxide led to high sound absorption, which significantly impeded the sound-speed measurements on carbon dioxide and its mixtures; pre-condensation may have also affected the results for some measurements near the dew line. Thus, in contrast to the standard operating procedure for speed-of-sound measurements with a spherical resonator, non-radial resonances at lower frequencies were taken into account. Still, the data show a comparatively large scatter, and the usual repeatability of this general type of instrument could not be realized with the present measurements. Nonetheless, the average relative combined expanded uncertainty (k = 2) in speed of sound ranged from (0.042 to 0.056)% for both mixtures, with individual state-point uncertainties increasing to 0.1%. These uncertainties are adequate for our intended purpose of evaluating thermodynamic models. The results are compared to a Helmholtz energy equation of state for carbon capture and storage applications; relative deviations of (-0.64 to 0.08)% for the (0.49896 argon + 0.50104 carbon dioxide) mixture, and of (-1.52 to 0.77)% for the (0.25019 argon + 0.74981 carbon dioxide) mixture were observed.