Measurement of the speed of sound in near-critical n-dodecane at temperatures from (433 to 679) K and pressures up to 10.0 MPa

As one of higher n-alkanes, n-dodecane is an important component of surrogate fuels for aviation kerosene, of which the accurate knowledge of its thermophysical properties is necessary for industrial application. The speed of sound in n-dodecane was measured by the Brillouin light scattering (BLS) in the vicinity of the critical point, of which the examined regions are T = (433.49 to 678.84) K along seven isobaric lines at p = (1.85, 2.0, 2.2, 4.0, 6.0, 8.0, and 10.0) MPa. The relative expanded uncertainty of BLS experimental system is estimated to be less than 1.2% with the confidence level of 95% (coverage factor, k = 2). Polynomial representations for the speed of sound in liquid n-dodecane was fitted by the experimental results, and the average absolute deviation and maximum absolute deviation are 0.70% and 1.96%, respectively. Moreover, the accuracy of the multiparameter equation of state proposed by Lemmon were assessed by the experimental speeds of sound in the whole investigated p-T region.