Rapid Measurements of Thermodynamic Properties for Alternative Refrigerants with Vibrating-Tube Densimeter

Abstract

More than 2000 PVT data in the liquid phase, vapor phase, and at saturation boundaries have been obtained for pure compounds of several alternative refrigerants. In addition, more than 1000 liquid-density data have been obtained for several binary and ternary mixtures. The alternative refrigerants measured in the present study include CF 3 OCH 3 (trifluoromethyl methyl ether) and CF 3 CF 2 OCH 3 (pentafluoroethyl methyl ether), which are hydrofluoroethers developed by RITE (the Research Institute of Innovative Technology for the Earth, Japan), and typical hydrocarbons, such as propane, n-butane, isobutene, and their binary and ternary mixtures. The measurement uncertainties are estimated to be 3 to 7 mK for temperature, 0.26 kPa or 0.022% whichever is greater for pressure, and 0.07 kg · m −3 or 0.024% whichever is greater for density. The present measurement system took only a few minutes to get one PVT datum, and one or two days to complete all the measurements for a single fluid at temperatures from 240 to 380 K and at pressures up to 7 MPa. In addition, an empirical equation of state (EoS) for the liquid phase was developed on the basis of the present data, and the EoS nicely reproduces not only the present data but also existing data reported by other researchers.

Automated Densimeter for the Rapid Characterization of Industrial Fluids

“…The instrument is based on a vibrating-tube densimeter. This method of measuring density is well-known and widely used. − Because the measurement technique is not absolute, the accuracy of the data relies greatly on the accuracy of the calibration used to relate the response of the instrument to the measured density, and we describe calibration protocols. The apparatus described here was developed to measure a wide range of fluids in the compressed liquid state, and to do so in a highly automated manner such that the measurement of a complete liquid surface can be made with little operator intervention.…”

Utilization of a High-Pressure Vibrating Tube Densimeter for Liquids at Temperatures Down to 100 K

“…Kayukawa et al [ 9 , 10 ] performed measurements of the evacuated U tube at the end of each investigated isotherm. Bouchot and Richon [ 51 ] consider the temporal shift of by recalibrating the vacuum oscillation at a reference temperature, and Kano et al [ 11 ] account for the aging of their densimeter using the most recent vacuum values.…”

“…Anton Paar, a leading manufacturer of vibrating tube densimeters, distributed the DMA 602 HTP model rated for temperatures from (73.15 to 423.15) K. However, its distribution has been discontinued, and it is likely that the model was never used at temperatures below 243.15 K [ 7 ]. The first applications of a VTD at temperatures as low as 240 K have been presented by Kayukawa et al [ 8 – 10 ] and Kano et al [ 11 ], where density measurements were performed using a modified DMA 512 of Anton Paar. More recently, Jiao et al [ 12 ] published an extended calibration of a VTD for temperatures from (203 to 423) K. The same system was later used for measurements in the temperature range from (203 to 293) K by Tenardi et al [ 13 ].…”

“…Low-temperature vibrating tube densimeters could be used in laboratory applications and in the field, where high-precision densimeters cannot be readily utilized. Potential cryogenic applications [ 39 ] would be, for example, investigations of new or improperly studied refrigerants [ 11 – 13 ], process monitoring and quality assurance of cryogenic product chains, or density measurements along the liquefied natural gas value chain [ 40 ]. Therefore, in this work, a targeted low-temperature study has been performed to specifically evaluate the functionality and accuracy of the DMA HPM temperatures as low as 100 K.…”

Relative Permittivity Measurements of Trifluoromethyl Methyl Ether and Pentafluoroethyl Methyl Ether

“…Further investigations for using HFEs as alternative refrigerants have been reported, [2][3][4] and a short review regarding their use as CFC replacements was published by Bivens and Minor. 5 While the environmental impact, 6,7 critical properties, [8][9][10][11] thermal conductivities, 12,13 vapor pressures, 10,11,14 and other thermodynamic properties [15][16][17] of many fluoroethers have been studied, little work has been carried out to investigate the fundamental solvent properties of these fluids. Lagalante et al 18 measured the Kamlet-Taft thermosolvatochromic parameters of several HFEs and their azeotropic mixtures at (260 to 343) K. In addition, several Japanese research groups have measured the relative permittivities of a range of C 3 and higher fluorinated ethers 19,20 (reported measurements do not include HFE 245mc).…”