Liu Tingting, Wang Shu, Zhu Ming
School of Electronic Information and Communications, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China.
J Acoust Soc Am. 2017 Mar;141(3):1844. doi: 10.1121/1.4978246.
The effective specific heat (ESH) is the "footprint" of acoustic relaxation processes in gases, and is characterized by a semicircle curve that is dependent on the acoustic frequency in the complex plane. In this paper, the ESH of the molecular relaxation process of a gas mixture is decomposed to obtain the relaxation contributions of the individual gas components. The decomposed ESHs obtained by the proposed method have the same complex-plane curves as the ESHs of the corresponding pure gases; thus, the ESH curve of the mixture can be obtained by the sum of the ESH curves of the corresponding pure gases. This conclusion not only provides a theoretical foundation for the existing gas sensing method based on acoustic spectral peaks, but can also be used to identify gas components in mixtures. The connecting lines of the minimum points of the ESH curves were used to quantitatively detect carbon dioxide and methane in dry air, and to monitor contaminant gases in natural gas.
有效比热（ESH）是气体中声弛豫过程的“印记”，其特征是在复平面上依赖于声频的半圆曲线。本文对气体混合物分子弛豫过程的ESH进行分解，以获得各气体组分的弛豫贡献。通过该方法得到的分解后的ESH在复平面上具有与相应纯气体的ESH相同的曲线；因此，混合物的ESH曲线可通过相应纯气体的ESH曲线之和得到。这一结论不仅为现有的基于声谱峰的气体传感方法提供了理论基础，还可用于识别混合物中的气体成分。利用ESH曲线最低点的连线对干燥空气中的二氧化碳和甲烷进行定量检测，并对天然气中的污染气体进行监测。
