A novel non-intrusive microcell for sound-speed measurements in liquids. Speed of sound and thermodynamic properties of 2-propanone at pressures up to 160 MPa

https://doi.org/10.1016/j.jct.2003.12.001Get rights and content

Abstract

A novel high-pressure, ultrasonic cell of extremely reduced internal dimensions (∼0.8 · 10−6 m3) and good precision for the determination of the speed of propagation of sound in liquids was conceived and built. It makes use of a non-intrusive methodology where the ultrasonic transducers are not in direct contact with the liquid sample under investigation. The new cell was used to carry out speed of sound measurements in 2-propanone (acetone) in broad ranges of temperature (265<T/K<340) and pressure (0.1<p/MPa<160). (p,ρ,T) data for acetone were also determined but in a narrower T,p range (298 to 333 K; 0.1 to 60 MPa). In this interval, several thermodynamic properties were thus calculated, such as: isentropic (κs) and isothermal (κT) compressibility, isobaric thermal expansivity (αp), isobaric (cp) and isochoric (cv) specific heat capacity, and the thermal pressure coefficient (γv). Comparisons with values found in the literature generally show good agreement.

Introduction

Measurements of the speed of sound (SS), u, in liquids have proven to constitute a powerful source of valuable information about the thermophysical properties of chemical substances and their mixtures [1], [2]. Most of the SS data reported in the literature have been obtained via so-called intrusive or invasive methods, where both the transmitter and receiver of the acoustic wave are in direct contact with the media under investigation [3], [4], [5], while in a few cases non-intrusive methods have been used [5], [6], [7], [8], [9]. The non-intrusive SS cell used in the current work is distinct from other non-intrusive ones in two respects: (a) no long buffer rods are used (instead, it presents a unique internal shape) and; (b) the internal volume was decreased by one or two orders of magnitude. Commonly, the volume of the liquid to be used is relatively great (typically, of the order of tens or hundreds of cm3). The present work reports the development made at the ITQB laboratories in Oeiras of an ultrasonic cell and its apparatus for measuring the speed of sound propagation in liquids, which makes use of a non-intrusive method using an extremely reduced liquid volume (∼0.8 · 10−6 m3). For this purpose, we designed and built a compact microcell that permits the measurements to be performed by locating the transducers (piezoelectrics) outside the liquid under study. The main advantages of this methodology over traditional invasive and large-volume methods are: (i) the possibility of undertaking measurements on almost any type of liquid, even if it is aggressive or reactive to the piezoelectric materials; (ii) the avoidance of possible damage to the piezoelectrics and/or their electric contacts upon pressurization; (iii) the easy generation of high pressures; (iv) the possibility of undertaking studies in metastable regimes, e.g., liquids under tension and/or supercooled; (v) the ability to obtain measurements of SS in very expensive fluids, e.g., isotopically substituted ones. The three latter points are a direct consequence of the extremely reduced volumes involved.

With the dual purpose of testing the novel microcell and associated methodology as well as determining extended high-accuracy data for an important fluid, acetone (2-propanone) was chosen to carry out SS measurements in a broad range of temperature (265<T/K<340) and pressure (0.1<p/MPa<160). Due to a surprising lack of extensive high quality data for this compound (considering its importance and popular use) even at low pressure, we have also measured at the REQUIMTE laboratories in Caparica its SS up to 60 MPa using a high-accuracy standard technique [3] which makes use of a double pulse-eco method. To the best of our knowledge there exists only one report [10] on the pressure dependence of the speed of sound in acetone at three isotherms.

This new microcell will be very useful in systematic investigations of the physical properties of various liquids and their mixtures under extreme (p,T) conditions, especially if speed of sound data can be combined with those of density. To this end, a more detailed analysis of the data from the literature revealed that precise density data for acetone [11], [12], [13], [14] are only known for very limited temperature and pressure values (mostly at 298 K and 0.1 MPa) and there is, thus, a need to perform more systematic measurements of density. Therefore, we have also carried out such measurements in the temperature range (298 to 333) K and up to 60 MPa. Kooner and Van Hook [15] investigated the deuterium isotope effect on several thermodynamic properties of acetone (perprotonated (-h) versus perdeuterated (-d)). The combined results of the speed of sound and density allowed us to calculate other physical properties of acetone such as isoentropic (κs) and isothermal (κT) compressibilities, isobaric thermal expansivities (αp), isobaric (cp) and isochoric (cv) specific heat capacities and thermal pressure coefficients (γv). Whenever available, these values are compared with literature data obtained via other methods.

Section snippets

Novel acoustic cell

In order to measure the speed of propagation of sound waves in liquids using a non-intrusive method, a new cell was designed and built (figure 1). It consists roughly of a 316 stainless steel hollow, thick-wall cylinder (diameter and length are approx. 30 mm and 36 mm, respectively) where two 1 MHz piezoelectric transducers (PZT), one acting as a transmitter and the other as a receiver, are housed in specially designed compartments in the outer section of the cylinder. They are firmly fixed to

Results and discussion

The measured values of the speed of sound and densities of acetone as a function of temperature and pressure are shown in FIGURE 3, FIGURE 4, FIGURE 5. In the case of the SS, results obtained with this novel cell are compared with those using the standard pulse-eco method (figure 4). Although physical and thermodynamic properties of acetone have been studied for many years, it still appeared that most of the work has been done at room temperature and atmospheric pressure. In particular, using

Conclusions

The values of calculated thermodynamic properties of acetone are generally in good agreement with the most reliable data found in the literature proving the high quality of the experimentally measured densities and speeds of sound. This, in turn, proves the usefulness of the new microcell for speed of sound measurements in broad temperature and pressure ranges.

Acknowledgements

This work was financially supported by Fundação para a Ciência e Tecnologia, Portugal, under contract POCTI/EQU/34955. R.G.A. and J.M.S.S.E. are grateful to Fundação para a Ciência e Tecnologia for doctoral fellowships.

References (30)

  • P.F. Pires et al.

    J. Chem. Thermodyn.

    (1999)
  • J.L. Daridon et al.

    J. Chem. Thermodyn.

    (1998)
  • V. Kozhevnikov et al.

    Fluid Phase Equilib.

    (1996)
  • H.T. French

    J. Chem. Thermodyn.

    (1989)
  • R. Malhotra et al.

    J. Chem. Thermodyn.

    (1991)
  • A. Lainez et al.

    J. Chem. Thermodyn.

    (1987)
  • J.P.M. Trusler

    Physical Acoustics and Metrology of Fluids

    (1991)
  • G. Douhéret et al.

    Chem. Phys. Chem.

    (2001)
  • S.J. Ball et al.

    Int. J. Thermophys.

    (2001)
  • R.C. Asher

    Ultrasonic Sensors

    (1997)
  • H.J. McSkimin
  • J.P. Petitet et al.

    Int. J. Thermophys.

    (1983)
  • H.F. Eden et al.

    Acustica

    (1960)
  • J. Timmermanns

    Physico-Chemical Constants of Binary Systems

    (1950)
  • H. Pöhler et al.

    J. Chem. Eng. Data

    (1997)
  • Cited by (46)

    • Influence of temperature and pressure on the density and speed of sound of N-ethyl-2-hydroxyethylammonium propionate ionic liquid

      2019, Journal of Chemical Thermodynamics
      Citation Excerpt :

      The cell was calibrated by measuring the speed of sound in water [27] and toluene [27], for the overall temperature and pressure ranges T = (298.15–348.15) K, and p = (0.1–20) MPa, using a total of 156 data points. The calibration equation from Gomes de Azevedo and coworkers’ [28], already reported by the authors in a previous work [15], was used. Taking in consideration the temperature, pressure, and the calibrating fluids speed of sound uncertainties, the combined standard uncertainty in the reported speed of sound values was estimated to be uc(u) = 1.6 m.s−1.

    • SAFT-VR-Mie with an incorporated polar term for accurate holistic prediction of the thermodynamic properties of polar components

      2018, Fluid Phase Equilibria
      Citation Excerpt :

      This proposal can be justified by considering speed of sound data for 3 linear C5 esters and 2 linear C6 esters in Fig. 2. The presented data show that the largest relative difference between the data for the three isomers is 3% (with experimental uncertainties averaging only 0.08% [38–48]), and that data for each component follow a similar trend with temperature. Lafitte et al. [9] demonstrated that typical deviations in speed of sound predictions for models other than SAFT-VR Mie are of the order of 10%.

    View all citing articles on Scopus
    View full text