Compressed liquid density measurements of dimethyl ether with a vibrating tube densimeter

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Abstract

A measurement system for compressed liquid densities over the temperature range of (293 to 373) K with pressures up to 70 MPa has been developed in this work. The core component of the system is a commercial vibrating tube densimeter (DMA-HPM) and the system was calibrated by water and vacuum via the method of Lagourette et al. Compressed liquid densities of dimethyl ether have been measured along nine isotherms between (293.84 and 372.94) K up to 70 MPa with the densimeter system as a function of temperature and pressure. The experimental data obtained in this work were correlated to the Tait equation with an average absolute percentage deviation of 0.014%. Also, the Tait equation was compared with the literature data.

Highlights

► A density measurement system based on Anton Paar DMA-HPM was developed in this work. ► Compressed liquid densities of dimethyl ether up to 373 K and 70 MPa were measured. ► The data were correlated to a Tait-type equation with an AAD value of 0.014%.

Introduction

Dimethyl ether (DME, CAS number 115-10-6) is an important chemical which has been widely used in many engineering applications, such as aerosol propellant, assistant solvent, vesicant and so on. Furthermore, dimethyl ether is regarded as a potential environmentally friendly alternative fuel for its lager oxygen content and lower emissions of SOx, NOx and 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. The thermophysical properties of dimethyl ether are indispensable for optimum design of energy-conversion systems and selection of the refrigerant. Our group has already acquired a lot of experimental data for dimethyl ether on various thermophysical properties, such as vapor pressure [2], critical properties and saturation densities [3], surface tension [4], saturated liquid viscosity [5], liquid thermal conductivity [6] and gaseous thermal conductivity [7].

The compressed liquid density data of dimethyl ether are still limited [8], [9], [10], [11]. Three earlier available experimental sources were obtained using vibrating tube apparatus: Bobbo et al. [8] measured compressed densities at temperatures from (283.15 to 353.15) K at pressures up to 35 MPa. Ihmels and Lemmon [9] measured the densities at temperatures from (273 to 523) K at pressures up to 40 MPa. Outcalt and McLinden [10] measured the compressed densities over the temperature range of (270 to 470) K and pressures up to 46 MPa. Recently, Tanaka and Higashi [11] measured the density of dimethyl ether from (310 to 360) K at pressures up to 5 MPa in the liquid phase with a metal-bellows calorimeter. For this reason, an experimental system for the measurement of the densities of compressed liquids in the temperature range of (293 to 373) K with pressures up to 70 MPa has been developed. The system was based on the vibrating tube method [12] and its measurement capability nicely complements other apparatus developed in our research group for PVT properties [13]. In this work, compressed liquid density data of dimethyl ether have been investigated to prove the capability of the apparatus. On the other hand, with the new density data the pressure range was extended up to 70 MPa.

Section snippets

Chemical

The sample of dimethyl ether was provided by Shandong Jiutai Chemical Co. Ltd. of China. The mass purity stated by the manufacturer 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.

Apparatus

The schematic diagram of the experimental system developed in this work is shown in figure 1. The compressed liquid density data were measured with a high temperature

Results and discussion

Compressed liquid densities of dimethyl ether were measured from (293.84 to 372.94) K, with pressures up to 70 MPa. A total of 108 points were obtained, as listed in table 1. The density data obtained in this work were correlated to the Tait equation [23]:ρ=ρ01-CTlnBT+pBT+p0,where for the parameters BT and CT, the following temperature dependences are used, respectively [14]:BT=b0+b1TE+b2TE2+b3TE3,CT=c0+c1TE.As shown in above equation, a reference state (ρ0 and p0) is required. A four-parameter

Conclusions

In this work a vibrating tube densimeter system has been developed for temperatures up to 373 K and pressures up to 70 MPa. The compressed liquid densities of dimethyl ether have been investigated along nine isotherms in the temperature range between (293 and 373) K and pressures up to 70 MPa using this experimental system. As there are no experimental data for the pressures higher than 46 MPa reported, the present work extends the pressure range of the density study on dimethyl ether. The density

Acknowledgements

This research is supported by the Hi-Tech Research and Development Program of China (No. 2009AA05Z107), the Research Fund for the Doctoral Program of Higher Education (No. 20090201110008) and the Chinese-Russian (NSFC-RFBR) scientific co-operation project (No. 50911120032).

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