The speed of sound in nitrogen at temperatures betweenT=250 K andT=350 K and at pressures up to 30 MPa

Speeds of sound in {(1−x)CH4+xN2} with x=(0.10001, 0.19999, and 0.5422) at temperatures between 170K and 400K and pressures up to 30MPa

“…In non-relaxing gases at pressures below roughly 1 MPa, the amount Dg 0n by which the observed half width exceeds the calculated half width is typically less than 10 À5 f 0n . However, this deteriorates with increasing pressures and values of 5 AE 10 À5 f 0n are more typical in our resonator at p = 20 MPa [10]. Initial analysis of the present results showed large excess half widths at low pressures; this is a clear indication that vibrational relaxation occurred in the gas and raises the question as to whether or not this relaxation gave rise to significant dispersion.…”

“…The results, which are given in table 2 and figure 1, indicate that s 12 was a rapidly increasing function of temperature. At T = 170 K, where s 12 and s 11 are similar in magnitude, the experimental half widths served to define s 12 q n with an uncertainty of around 15 ls AE mol AE m À3 and gave a value b = 1 AE 10 5 similar to that found in non-relaxing gases [10]. At higher temperatures, as s 11 declines and s 12 appears to increase, the sensitivity of the analysis declined rapidly so that at T = 250 K, the uncertainty of s 12 was about 100 ls AE mol AE m À3 .…”

An apparatus for the determination of speeds of sound in fluids

“…The sound speed in compressed nitrogen has been measured by several authors, but only some of them have obtained highly accurate data, as for example Costa Gomes and Trusler [29] with uncertainties from 0.001% to 0.01%; Kortbeek et al [30], 0.02%; and Meier [31], 0.012%. The first two groups of authors have measured the speed of sound with a spherical resonator, while the last reference contains experimental data determined by the pulse-echo technique.…”

“…The first two groups of authors have measured the speed of sound with a spherical resonator, while the last reference contains experimental data determined by the pulse-echo technique. [21] as a function of pressure: s, This work; h, reference [29]; and, +, reference [31]. At the working frequency of 8 MHz the vibrational contribution to the effective heat capacity of nitrogen is completely absent.…”

“…At the working frequency of 8 MHz the vibrational contribution to the effective heat capacity of nitrogen is completely absent. Thus, in contrast to water where the speed of sound is independent of the frequency up to 25 MHz [32], the experimental sound velocities of nitrogen were corrected using the equation given in reference [29] to the zero frequency value, which is related to other thermodynamic properties.…”