An experimental study of PVTx properties in the gas phase for binary mixtures of HFO-1234yf and HFC-134a

doi:10.1016/j.fluid.2014.10.047

Fluid Phase Equilibria

Volume 385, 15 January 2015, Pages 25-28

https://doi.org/10.1016/j.fluid.2014.10.047 Get rights and content

Abstract

An experimental study of the pressure–volume–temperature-composition (PVTx) properties in the gas phase for binary mixtures of 2,3,3,3-tetrafluoropropene (HFO-1234yf)+ 1,1,1,2-tetrafluoroethane (HFC-134a) was conducted in the range of temperatures from 298.58 to 403.24 K, pressures from 567.5 to 3171.2 kPa, densities from 0.258 to 1.258 mol dm⁻³, and compositions from 0.0380 to 0.8641 mole fractions of HFC-134a. The measurements were performed with an isochoric cell apparatus. The uncertainties in the present work were estimated to be ±1.5 kPa for pressure, ±6 mK for temperature, and ±0.15% for composition. On the basis of the experimental PVTx property data, a truncated virial equation of state was developed for the binary HFO-1234yf/HFC-134a system. This equation reproduced the experimental data in the gas phase within ±0.20% in pressure and within ±0.23% in density.

Introduction

The Montreal Protocol establishes schedules for phasing out the manufacture of chlorine-containing refrigerants, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which have been implicated in stratospheric ozone depletion [1], [2]. And the European Union decides to ban refrigerants with a global warming potential (GWP) over 150 in automobile air conditioning to lower the impact on the environment. The commonly used fluid HFC-134a has an ODP = 0, but a GWP is 1430 as compared to that of carbon dioxide (CO₂). HFO-1234yf is a new refrigerant with a zero ODP and its GWP is approximately 12 for a 20 year time horizon and 4 for a 100 year time horizon. One of the main drawbacks of HFO-1234yf is its mildly flammability. By adding HFC-134a to HFO-1234yf, the mixture can become non-flammable with GWP still less than 150. Hence, it can solve successfully the major issue of HFO-1234yf’s flammability while it meets the mobile air-conditioner directive requirement.

Reliable information about the thermodynamic properties of HFO-1234yf/HFC-134a is essential for its application as a working fluid in the refrigeration system. PVTx data are required as one of the most important properties of information in evaluating the performance of refrigeration cycles and determining their optimal compositions. The vapor–liquid equilibrium properties of HFO-1234yf/HFC-134a system was presented by Kamiaka [3], and ‘drop-in’ performance of the mixture was measured in a heat pump bench tester by Lee [4]. In this study, a total of 94 gaseous PVTx data for the binary HFO-1234yf/HFC-134a system were measured using the isochoric method at temperatures from 298.58 to 403.24 K. To our knowledge, no data are currently available on the PVTx properties of this binary mixture.

Section snippets

Experimental

The experimental apparatus includes a sample cell, a high-accuracy thermostatic bath, a pressure measurement system, a temperature measurement system, and a vacuum system. It is the same as the one described previously [5], and it is only briefly described here. The temperature in the thermostatic bath can be varied from 230.15 to 453.15 K. The bath fluid is alcohol, distilled water, or silicon oil, depending on temperature range. The temperature measurements are made with a four-lead 25-Ω

Results and discussion

In this study, a total of 94 PVTx data were obtained at temperatures from 298.58 to 403.24 K along 7 independent isopleths. Results of the isochoric measurements are given in Table 2.

To represent the experimental PVTx data in the gas phase of the binary HFO-1234yf/HFC-134a system, a truncated virial equation of state was developed. Since the applicable density range of the present model is up to 1.258 mol dm⁻³, the fourth and higher viral terms are truncated [7]. The virial-type equation of state

Conclusion

In this work, the PVTx properties in the gas phase for the binary HFO-1234yf/HFC-134a system have been measured using the isochoric method. The maximum uncertainties were estimated to be ±1.5 kPa, ±6 mK and ±0.15% for pressure, temperature, and density, respectively. A total of 94 PVTx data were obtained along seven independent isopleths: 0.0380, 0.2445, 0.2565, 0.5430, 0.6236, 0.8220 and 0.8641 mole fractions of HFC-134a.

By using the experimental values, a virial-type equation of state of the

Acknowledgements

We are greatly indebted to Juhua Group Corporation (China) for providing the 2,3,3,3-tetrafluoropropene (HFO-1234yf) and 1,1,1,2-tetrafluoroethane (HFC-134a) samples. Financial support of the National Natural Science Foundation of China (Grant No. 51376156) is also gratefully acknowledged.

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The pvTx property is one of the most important thermophysical properties of mixtures, especially for developing equation of state (EOS) and measuring the other thermophysical properties (such as thermal conductivity, surface tension and viscosity). Unfortunately, only one data source for the gaseous pvTx properties of R134a/R1234yf mixtures was reported by Chen et al. (Chen et al., 2015) measured by using an isochoric apparatus. The experimental measurements at the mole fractions of R134a from 0.038 to 0.864 were performed in the temperature range from (298 to 403) K and at pressures up to 3.17 MPa.
In the present study, the accurate determination of the vapor phase pvTx behavior of binary mixtures of 1,1,1,2-Tetrafluoroethane (R134a) + 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) by using a Burnett apparatus was demonstrated. Measurements have been performed over the temperature range from (303 to 388) K and at pressures up to 5023 kPa covering the mole fractions of x_R134a = (0.000, 0.099, 0.328, 0.523, 0.726, 0.919, 1.000). The combined expanded uncertainties of temperature, pressure, mole fraction and vapor density with a level of confidence of 0.95 (k = 2) were estimated to be 24 mK, 1.6 kPa, 0.01 and within 0.2% over the entire temperature, pressure and mole fraction ranges, respectively. In order to facilitate practical industrial applications and explore the thermophysical behavior of the second and third virial coefficients, the experimental vapor density data of this work were used to develop the virial equation of state with the average absolute deviation of compressibility factor lower than 0.52% for each composition. Furthermore, the obtained gaseous pvTx properties of R134a/R1234yf mixtures were compared with the multi-parameter equation of state of REFPROP 10.0 (Lemmon et al., 2018) and the relative deviations were less than 1.2%.
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At present, the difficulty in the research of auto cascade refrigeration system lies in the selection of the mixed refrigerant ratio and the design of system process. Accurate thermodynamic data is the key to solve those problems. In this paper, isothermal vapor liquid equilibrium (VLE) behavior was experimentally studied for the strongly-zeotropic ternary mixture 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14) at 253.15 K, 263.15 K, and 273.15 K. The pressures and the vapor mass fractions were found to be thermodynamically consistent and were satisfactorily correlated with the NRTL-RK model and the MUNIFAC-SRK model. The average absolute relative deviations of pressure (AARD-p), and the average absolute deviations of vapor phase mass fraction (AAD-y₁, AAD-y₂ and AAD-y₃) are less than 0.25%, 0.0032, 0.0048 and 0.0040 for the MUNIFAC-SRK model, respectively, which are better than those of 0.4%, 0.0138, 0.0198 and 0.0049 for the NRTL-RK model. The results of the MUNIFAC-SRK model showed excellent agreement with the experimental values. The isothermal three-dimensional VLE behavior and the isothermal-isobaric ternary VLE diagrams under 1500 kPa were also established using a flash calculation method.
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An experimental study of PVTx properties in the gas phase for binary mixtures of HFO-1234yf and HFC-134a

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Acknowledgements

Int. J. Refrig.

Int. J. Refrig.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.