Gas equilibrium heat capacity synthesis under the influence of acoustic relaxation process and its application in gas detection

• 来源期刊: 声学学报（英文版）
• 年，卷（期）: 2019,（4）
• 页码范围: 386-402
• 页数: 17页
• 语种: 英文

摘要

In an excitable gas,the molecular vibration relaxation process caused by an acoustic disturbance leads the equilibrium heat capacity to the effective one that depends on the acoustic frequency,resulting in acoustic dispersion and acoustic relaxational absorption.Based on the algorithm of synthesizing a single-relaxation process,we develop a synthesizing method to get the equilibrium heat capacities of excitable gases from the two-frequency acoustic speed and absorption measurements.The two measurement frequencies are selected in the range where the acoustic relaxational absorption is obvious.The method can obtain the heat capacities of internal and external degrees of freedom of gas molecules respectively,and effectively eliminate the influence of the acoustic relaxation process on the measurement results of excitable gas heat capacity.For various gases,consisting of CO2,CH4,Cl2,N2 and O2 at room temperature,the gas heat capacities obtained in this paper agree with the thermodynamic theoretical calculations based on the Planck-Einstein formula,and the maximum relative error is 3.51％ in comparison to the experimental result.The synthesized heat capacities of rotation and vibration can be applied to the detection of gas molecular geometry,vibration frequency and mole fractions of gas mixtures.