Viscosity for Aqueous Li₂SO₄ Solutions at Temperatures from 298 to 575 K and at Pressures up to 30 MPa

Abstract

Viscosities of four aqueous Li 2 SO 4 solutions [(0.10, 0.28, 0.56, and 0.885) mol‚kg -1 ] have been measured in the liquid phase with a capillary flow technique. Measurements were made at four isobars [(0.1, 10, 20, and 30) MPa]. The range of temperatures was from (298 to 575) K. The total uncertainties of viscosity, pressure, temperature, and concentration measurements were estimated to be less than 1.5%, 0.05%, 10 mK, and 0.014%, respectively. The reliability and accuracy of the experimental method were confirmed with measurements on pure water for three isobars [(10, 20, and 30) MPa] and at temperatures between (298 and 575) K. The experimental and calculated values from the IAPWS (International Association for the Properties of Water and Steam) formulation for the viscosity of pure water show excellent agreement within their experimental uncertainty (AAD is about 0.51%). A correlation equation for viscosity was obtained as a function of temperature, pressure, and composition by a least-squares method from the experimental data. The AAD between measured and calculated values from this correlation equation for the viscosity was 0.7% for pure water and 0.74% for the solutions. The measured values of viscosity at atmospheric pressure were compared with the data reported in the literature by other authors.

Viscosity

“…Figure 6.1 shows a schematic diagram of a typical capillary viscometer (Pepinov et al 1978(Pepinov et al , 1979a(Pepinov et al ,b, 1983(Pepinov et al , 1986(Pepinov et al , 1988(Pepinov et al , 1989Abdullaev et al 1990Abdullaev et al , 1991aAkhundov et al, 1990aAkhundov et al, ,b, 1991bAbdullaev, 1991;Zeynalova et al 1990Zeynalova et al , 1991Pepinov, 1992;Iskenderov, 1996;Azizov, 1996Azizov, , 1999Azizov and Akhundov, 1997;Abdulagatov and Azizov, 2003, 2005a-d, 2006a,b, and Abdulagatov et al 2004, 2005. They all employed a very similar Abdulagatov and Azizov.…”

“…The inner surface of the capillary walls is perfectly polished with powders of successively smaller grain size (1 to 40 nm). The average capillary radius is measured using a weighing technique or/and by calibration (relative method, see Abdulagatov and Azizov, 2003) from the viscosity of a standard fl uid (pure water) with well-known viscosity values (IAPWS formulation, Kestin et al, 1984a). The correction for capillary radius, due to the meniscus curvature (surface forces in a capillary), is made.…”

“…The correction for capillary radius, due to the meniscus curvature (surface forces in a capillary), is made. Typical values (obtained by Abdulagatov and Azizov, 2003) of the capillary radius determined with both weighing and by the calibration techniques are 0.15091 mm and 0.15048 mm, respectively, resulting in a value for R 4 of (51.27 ± 0.59) × 10 −5 mm 4 . The length, L, of the capillary is measured with a microscope with an uncertainty of ±0.005 mm.…”

“…The length, L, of the capillary is measured with a microscope with an uncertainty of ±0.005 mm. Typically the fi nal value of the capillary length (obtained by Abdulagatov and Azizov, 2003), is 540.324 ± 0.005 mm. Flow time measurements are usually made electronically and the uncertainty in this value is never more than 0.1s (0.5%).…”

“…After a very careful analysis of the uncertainty of these quantities (Abdulagatov and Azizov, 2003), it is estimated that the combined relative uncertainty in measuring the viscosity (up to the highest temperature of 575 K) is 1.5% (in this chapter we use a coverage factor k = 2). Furthermore, the uncertainty associated with the measurement of the concentration is estimated to be 0.014%, while the maximum uncertainty in the pressure measurements is 0.05%.…”