Vapor–liquid equilibrium data for the difluoromethane (R32)–dimethyl ether (RE170) system at temperatures from 283.03 to 363.21 K and pressures up to 5.5 MPa

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Abstract

Isothermal vapour–liquid equilibrium data have been measured for the R32 + RE170 binary system at seven temperatures between 283.03 and 363.21 K, and pressures between 0.5 and 5.5 MPa. The experimental method used in this work is of the static-analytic type, taking advantage of two pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in the CEP/TEP laboratory. The data were obtained with uncertainties within ±0.02 K, ±0.0002 MPa and ±1% for molar compositions.

The isothermal P, x, y data are well represented with the Peng and Robinson equation of state using the Mathias–Copeman alpha function and the Wong–Sandler mixing rules involving the NRTL gE model.

Introduction

Industry needs new fluids to replace ozone-destroying refrigerants like chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Their use, production and distribution are ruled by the modification of the 1987 Montreal Protocol. CFCs are prohibited since 1996 for countries-members and the deadline for HCFCs which have lower ozone depletion potential is 2030.

A new system is studied in this paper. It contains R32 and RE170 that was proposed in the past by Charles Tellier (1828–1913). RE170 has been extensively used in industrial refrigeration, as much as ammonia, it has zero ozone depletion potential and can be associated to HFCs. R134a–RE170 system was previously investigated in our laboratory [1]. R32 being an alternative refrigerant used in air conditioning and refrigeration, it was interesting to study it with RE170 in order to verify if this new system could be an advantageous new candidate for refrigeration industry. This system belongs to the type II of the Scott and van Konynenburg classification [2].

Accurate knowledge of thermophysical properties of alternative refrigerants, like HFCs containing mixtures, is necessary to evaluate the performance of refrigeration cycles. As an answer to this request, the TEP laboratory has already published many experimental data concerning refrigerant mixtures, the most recent can be found in [1], [3], [4], [5], [6], [7], [8].

The new enclosed experimental results are fitted using the Peng and Robinson equation of state (PR EoS). Our data are compared to those of Fedele et al. [9] that were measured at three temperatures: 258.15, 273.15 and 293.15 K.

Section snippets

Materials

RE170 was obtained from Atofina (France) with a certified purity higher than 99.9 vol.%. R32 was purchased from Dehon (France) and has a certified purity higher than 99.95 vol.%. RE170 was carefully degassed before use to remove incondensable gases.

Apparatus

The apparatus used in this work is based on a static-analytic method with liquid and vapour phase sampling. This apparatus is similar to that described by Laugier and Richon [10] and Valtz et al. [1].

The equilibrium cell is contained in a liquid

Correlations

The critical temperatures (TC), critical pressures (PC), and acentric factors (ω), for each of the two pure components are provided in Table 1. Our experimental VLE data are correlated by means of homemade software TepThermosoft [12], developed by Armines, Ecole des Mines de Paris. We have used the PR EoS [13] to correlate the data.

To have accurate representation of vapour pressures of each component, we use the Mathias–Copeman alpha function [14] given below with three adjustable parameters,

Vapour pressures

The vapour pressures of pure RE170 were measured between 278.25 and 360.52 K. The experimental data were tabulated in a previous publication [1]. The Mathias–Copeman coefficients adjusted on these experimental data are reported in Table 2. The observed absolute relative deviation is less than 0.1%. Our RE170 experimental vapour pressures have been compared to literature experimental data [19], [20], [21], [22], [23], [24] in one of our previous studies [1]. The corresponding Mathias–Copeman

Conclusions

In this paper we present VLE data for the system R32 + RE170 at seven temperatures that are either below or above the R32 critical temperature. We used a static-analytic method to obtain our experimental data. We chose the Peng and Robinson EoS, with the Mathias–Copeman alpha function and the Wong–Sandler mixing rules involving the NRTL model to fit experimental data. The experimental results are given with following uncertainties: ±0.02 K, ±0.0002 MPa and ±1% for vapour and liquid mole fractions.

    List of symbols

    a

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