RESUMEN
Bubble point pressures of three binary mixtures at two compositions each have been measured utilizing a static method. The mixtures studied were: difluoromethane + 2,3,3,3 tetrafluoroprop-1-ene (R-32/1234yf), difluoromethane + (E)-1,3,3,3-tetrafluoroprop-1-ene (R-32/1234ze(E)) and 1,1-difluororethene + 2,3,3,3 tetrafluoroprop-1-ene (R-1132a/1234yf). For all the mixtures the minimum temperature measured was 270 K. The maximum temperatures measured for the R-32/1234ze(E), R-32/1234yf and R-1132a/1234yf mixtures were 360 K, 345 K and 325 K respectively. A total of 100 bubble point pressures are reported and compared to available literature data relative to the REFPROP database1. Additionally, the bubble point pressures obtained in this study are modeled using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. The PC-SAFT model parameters are reported as well as deviations of this work and literature data from the model.
RESUMEN
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.
RESUMEN
Difluoromethane (HFC-32, DFM), with a global warming potential (GWP) of 677, is of interest as a pure refrigerant and as a component in low-GWP refrigerant mixtures. Additionally, difluoromethane has recently been identified as a safe, liquefied-gas electrolyte material in batteries. Using state-of-the-art instruments for measurements, this paper presents new liquid-phase speed of sound and vapor-phase density data for difluoromethane. Two hundred and nine liquid-phase speed of sound values were measured using a dual-path pulse-echo instrument at temperatures from 230 to 345 K and pressures from 2.1 to 70 MPa. Accounting for all sources of uncertainty, the relative expanded combined uncertainty (k = 2) in the speed of sound ranged from 0.035 to 0.17%. One hundred and thirty-eight vapour-phase density values were measured using a two-sinker densimeter at temperatures from 240 to 340 K and pressures from 0.1 to 1.61 MPa with an uncertainty of 0.011 to 0.12%. These experimental data will be valuable in the ongoing development of a new fundamental thermodynamic equation of state for difluoromethane.
RESUMEN
Bubble point pressures of six binary mixtures at two compositions each have been measured utilizing a static method. The performance of the apparatus was characterized from bubble point measurements of R32 + R125 for which 19 literature studies are available for comparison. The mixtures studied were as follow: R1234yf + R134a, R134a + R1234ze (E), R1234yf + R1234ze (E), R125 + R1234yf, R1234ze (E) + R227ea and R1234yf + R152a. For each mixture measurements were conducted from 270 K to 360 K or to within approximately 10 K of the critical temperature of the pure component with the lower critical temperature. A total of 196 bubble point pressures are reported with combined expanded uncertainties (k = 2) ranging from 0.1% - 0.6%. The measured data are graphically compared to available literature data.
RESUMEN
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.
RESUMEN
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.