Reference Correlation for the Viscosity of Ammonia from the Triple Point to 725 K and up to 50 MPa

Abstract

This paper presents a new wide-ranging correlation for the viscosity of ammonia based on critically evaluated experimental data. The correlation is designed to be used with a recently developed equation of state, and it is valid from the triple point to 725 K, at pressures up to 50 MPa. The estimated uncertainty varies depending on the temperature and pressure, from 0.6% to 5%. The correlation behaves in a physically reasonable manner when extrapolated to 100 MPa, however care should be taken when using the correlations outside of the validated range.

Reference Correlation for the Thermal Conductivity of Ammonia from the Triple-Point Temperature to 680 K and Pressures up to 80 MPa

“…24 For this reason, and since we have the very accurate measurements by Tufeu et al 17 in the critical region, it was preferred not to include the near-critical isotherms of Golubev and Sokolova 25 (T 5 406, 414, and 423 K) and Needham and Ziebland 24 (411 K). Finally, since dissociation of ammonia has been observed above 700 K, 21 it was decided not to include the last two measurements of Golubev and Sokolova 25 (at T 5 723 K and 773 K). The measurements of Keyes, 26 performed in an axial heat-flow instrument, were also included in the primary dataset, as they are the only other set of gaseous measurements obtained up to T 5 523 K.…”

“…This crossover model requires the universal amplitude, R D 5 1.02 (2), the universal critical exponents, n 5 0.63 and g 51.239, and the system-dependent amplitudes G and j 0 . For this work, we adopted the values G 5 0.053 (2) and j 0 5 0.140 3 10 29 m, using the universal representation of the critical enhancement of the thermal conductivity by Perkins et al 52 When there are sufficient experimental data available in the critical region, the remaining parameter q 21 D may be found by regression. The dataset of Tufeu et al 17 contains data in the critical region, which were used to fit the effective cutoff wavelength q 21 D (m) simultaneously with the coefficients of Eq.…”

“…The dataset of Tufeu et al 17 contains data in the critical region, which were used to fit the effective cutoff wavelength q 21 D (m) simultaneously with the coefficients of Eq. (7) and to obtain the value for q 21 D of 4.0 3 10 210 m. The viscosity required for Eq. (8) was obtained by the recent correlation of Monogenidou et al 21 The reference temperature T ref , far above the critical temperature where the critical enhancement is negligible, was calculated by 31 which for ammonia is 608.34 K. Table 3 summarizes comparisons of the primary data with the correlation.…”

“…(7) and to obtain the value for q 21 D of 4.0 3 10 210 m. The viscosity required for Eq. (8) was obtained by the recent correlation of Monogenidou et al 21 The reference temperature T ref , far above the critical temperature where the critical enhancement is negligible, was calculated by 31 which for ammonia is 608.34 K. Table 3 summarizes comparisons of the primary data with the correlation. The average absolute percent deviation (AAD) of the fit is 2.67%, and its bias is 20.18%.…”

“…Following this, in 1988, Clifford and Tufeu 18 extended those measurements down to 300 K. Since then, new thermal-conductivity data have been published by Shamsetdinov et al, 19 and a new Helmholtz equation of state of Gao et al 20 has been developed. Furthermore, in Paper I, 21 a new reference correlation for the viscosity of ammonia was proposed. The goal of this work is to critically assess the available literature data and provide a wide-ranging correlation for the thermal conductivity of ammonia that is valid over gas, liquid, and supercritical states and that incorporates densities provided by the new equation of state of Gao et al 20 The analysis will be applied to the best available experimental data for the thermal conductivity.…”