The speed of sound in n-heptane was measured by the Brillouin light scattering (BLS) method. The examined region is T = (513.40 to 650.90) K along seven isobaric lines at p = (2.5, 3.0, 4.0, 5.0, 6.0, 8.0, and 10.0) MPa, which was near the critical point of n-heptane. The relative expanded uncertainty (k = 2) of BLS experimental system is estimated to be <0.013 for the speed of sound measurement. The variation tendencies of the speed of sound with increasing temperature and pressure were illustrated. Moreover, the calculated results from the multiparameter equation of state (EOS) proposed by Span and Wagner were employed to assess the experimental data in this paper. The absolute average of the deviations (AAD) between the experimental data and the calculated results is 1.22% in the whole investigated p–T region.
Xiong Zheng,Ying Zhang,Maogang He,Lili Liang,Xinxin He
Fatty acid ethyl esters (FAEEs) are the main components in some biodiesels, which are important alternatives of fossil fuels. In this paper, we carry out the measurements of the speed of sound in two FAEEs at the temperatures from (293.15 to 473.15) K and at the pressures up to 10 MPa, including saturated liquid and compressed liquid. The relative expanded uncertainty in the speed of sound is estimated to be less than 1.0% with coverage factor of k to be 2. The data in saturated liquid and compressed liquid are fitted into polynomials. For saturated liquid, the D AAD is 0.16% for ethyl hexanoate and 0.09% for ethyl octanoate. For compressed liquid, the D AAD is 0.31% for ethyl hexanoate and 0.16% for ethyl octanoate. The data were also used to assess the predictive ability of Wada’s model.
Ying Zhang,Qi Zhou,Taotao Zhan,Junshuai Chen,Maogang He
n -Pentane is one of the main components in many industrial fluids, and is widely used as the fuel. The speed of sound can be used for developing the Helmholtz energy formulation and calculating other thermodynamic properties, which has not been reported yet for supercritical n -pentane. In this paper, the speed of sound in supercritical n -pentane was measured by the Brillouin light scattering (BLS) technique within the temperature limits of (422.69–653.53) K along four isobars at p = (3.5, 6.0, 8.0, and 10.0) MPa. The relative uncertainty of our BLS experimental system is estimated to be less than 0.6% and the relative uncertainty of the reported speed of sound values is estimated to be 0.85% considering the influence of impurities in the sample. The dependences of the speed of sound on temperature and pressure were also analyzed. At the end, we compared the experimental data with the calculated values from the multiparameter EOS proposed by Span and Wagner and the Modified BWR EOS proposed by J. Ratanapisit and J.F. Ely. The AARD is 1.3% for the multiparameter EOS and 1.5% for the Modified BWR EOS, respectively.
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