2pPAb12. Comparison of sound-speed computation methods.

Session: Tuesday Afternoon, May 14

Time: 4:15

Author: George S. K. Wong
Location: Inst. for Natl. Measurement Standards, National Res. Council, Ottawa, ON K1A 0R6, Canada


The computation of sound speeds in nitrogen, oxygen, and methane was performed with two methods. Results from the traditional method that relied on virial coefficients B and their temperature derivatives T dB/dT, T[sup 2] d[sup 2]B/dT[sup 2], were compared with those given by a simplified method. At a pressure of 101.325 kPa, and at a temperature of -10 (degrees)C, the maximum sound speed deviations between the two methods are within 0.2% and -0.4% for nitrogen and oxygen, respectively. For methane, at the above pressure, and over the temperature range from zero to 450 (degrees)C, the maximum deviation is 1.2%. For the above gases, the sound-speed deviations between the methods are largest at low temperatures. It can be shown that by modifying the numerical values of the virial coefficients and their temperature derivatives, the sound-speed deviations between the two methods can be reduced substantially. For nitrogen, when B, T dB/dT, and T[sup 2] d[sup 2]B/dT[sup 2] are modified by multiplication factors of -0.1, 0.55, and 0.7, respectively, the difference between the sound speeds obtained with the two methods decreases to less than (plus or minus)0.05%. It is noted that the sign of the numerical value of B is reversed. Uncertainties of the results obtained with both methods were examined.

from ASA 131st Meeting, Indianapolis, May 1996