Gas phase PVT properties and second virial coefficients of dimethyl ether
Introduction
Dimethyl ether (DME) is an important chemical material which has many engineering applications such as aerosol propellant, assistant solvent, vesicant and so on. Furthermore, dimethyl ether is regarded as a promising clean alternative fuel for its lager oxygen content and lower emissions of SOx, NOx or particulates than conventional fuel when burning as well as its high-efficiency and non-petroleum based character [1]. It also has been suggested as an alternative refrigerant named as RE170. In these fields, the thermophysical properties of dimethyl ether are indispensable. A preliminary fundamental equation of state was derived by Ref. [2] and our group has also been done some research on vapor pressure, critical properties, saturation densities, surface tension, liquid viscosity and thermal conductivity of dimethyl ether recently [3], [4], [5], [6], [7], [8].
After a literature survey, a very limited data of second virial coefficients and gas phase PVT properties for dimethyl ether were found [9], [10], [11], [12], [13], [14], [15], [16]. In this work, a total of 126 experimental data were collected in the gas phase region for the temperature range of 328–403 K including 9 points in the super-critical region. Derived second virial coefficients were compared with the literature data.
Section snippets
Experimental
The sample of dimethyl ether was provided by Shandong Jiutai Chemical Co. Ltd. of China. The stated mass purity is better than 99.95%. In order to eliminate the effect of gaseous impurity, the sample was purified several times by freeze-pump-thaw cycles by using liquid nitrogen and a high vacuum (<0.01 Pa) pump.
The experimental apparatus used in this work is illustrated in Fig. 1. It consists of a Burnett apparatus, a thermostatic bath, a temperature measurement system, a pressure measurement
Results and discussion
A total of 126 gas phase PVT data for dimethyl ether along 16 isotherms in temperature range from 328 to 403 K and for pressures from 183 to 4733 kPa were obtained and the data surface is shown in Fig. 2.
All the PVT data were analyzed by Burnett analysis method along each isotherm with the cell constant obtained using helium. The experimental data along with the calculated compressibility factors and densities are given in Table 2. The density uncertainty was estimated to be within ±0.15%. The
Conclusions
A total of 126 gas phase PVT data for dimethyl ether were obtained using Burnett-isochoric method in the temperature range of 328–403 K, the pressure range of 183–4733 kPa and density range from 0.07 to 2.5 mol dm−3. The measurement uncertainty of temperature was estimated to be within ±10 mK and that of pressure was less than ±0.7 kPa. Second virial coefficients along 16 isotherms were obtained and a temperature relationship for the calculation of second virial coefficients was also given based on
Acknowledgements
This research is supported by the Research Fund for the Doctoral Program of Higher Education (No. 20090201110008) and the Fok Ying Tung Education Foundation Award (No. 111060).
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