Gas phase PVTx properties for binary mixtures of HFC-161 and HFC-134a

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Abstract

An experimental study of the pressure–volume–temperature–composition (PVTx) properties in the gas phase for binary mixtures of ethyl fluoride (HFC-161) and 1,1,1,2-tetrafluoroethane (HFC-134a) was conducted in the range of temperatures from 318.22 to 403.20 K, pressures from 1120.6 to 5767.0 kPa, densities from 0.494 to 3.974 mol dm−3, and compositions from 0.3203 to 0.9474 HFC-161 mole fractions. The measurements were performed with an isochoric cell apparatus. The uncertainties in the present work were estimated to be ±1.5 kPa for pressure and ±6 mK for temperature. On the basis of the experimental PVTx property data, a truncated virial equation of state was developed for the HFC-161/134a binary system. This equation reproduces the experimental data in the gas phase within ±0.18% in pressure and within ±0.32% in density.

Research highlights

► HFC-161/134a has potential as a working fluid in refrigeration system. ► The PVTx properties for HFC-161/134a have been measured. ► A virial-type equation of state for HFC-161/134a has been developed.

Introduction

With the increasing recognition of environment protection, a great deal of attention has been devoted to the negative environmental effect of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). It is strongly recommended to replace remaining CFCs and HCFCs with zero ozone depletion potential (ODP) refrigerants such as hydrofluorocarbons (HFCs). Ethyl fluoride or HFC-161 has a boiling point 235.85 K and critical temperature 375.31 K that are desirable for an HCFC-22 alternative. However, the flammability of HFC-161 lowers its potential as a refrigerant. 1,1,1,2-Tetrafluoroethane (HFC-134a) is nonflammable for it to serve as a replacement for CFCs and HCFCs in refrigeration application. Reliable information about the thermodynamic properties of HFC-161/134a is essential for its application as a working fluid in the refrigeration system. The vapor–liquid equilibrium properties of the mixtures as refrigerant containing HFC-161 are also discussed by Beyerlein, Kul et al. [1], [2], [3]. However, for the HFC-161/134a binary system, there are no published reports on its gas phase PVTx properties.

PVTx data are required as one of the most important types of information in evaluating the performance of refrigeration cycles and determining their optimal compositions. In the present study, we aim to measure a first set of PVTx properties in the gas phase of this important binary blend. A total of 111 gaseous PVTx data for the HFC-161/134a binary system were measured using an isochoric method in a wide range of temperatures from 318.22 to 403.20 K and corresponding pressures from 1120.6 to 5767.0 kPa.

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 [4].

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. Its temperature fluctuations are determined to be less than ±3 mK in 30 min. The temperature measurements

Results and discussion

In this study, a total of 111 PVTx data were obtained at temperatures from 318.22 to 403.20 K along 9 independent isopleths: 0.3203, 0.4301, 0.5191, 0.5217, 0.5472, 0.7135, 0.8840, 0.9206 and 0.9474 HFC-161 mole fractions. A temperature correction to the densities was made to compensate for the thermal expansion of the sample cell. Results of the isochoric measurements are given in Table 1.

To represent the experimental PVTx data in the gas phase of the HFC-161/134a binary system, a truncated

Conclusions

In this work, the PVTx properties in the gas phase for the HFC-161/134a binary 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 111 PVTx data were obtained along nine independent isopleths: 0.3203, 0.4301, 0.5191, 0.5217, 0.5472, 0.7135, 0.8840, 0.9206 and 0.9474 HFC-161 mole fractions.

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

Acknowledgements

We are greatly indebted to Zhejiang Chemical Industry Research Institute for providing the ethyl fluoride (HFC-161) and 1,1,1,2-tetrafluoroethane (HFC-134a) samples. Financial support of National Basic Research Program of China (project no. 2010CB227304) is also gratefully acknowledged.

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