Abstract

Subject of study. This study is devoted to the research and development of a fiber-optic method for identifying a substance by its thermal characteristics and determining the phase of a substance in a gas-liquid mixture flow. Aim of study. The purpose of this study is to develop a fiber-optic sensing element with a single compact design and the possibility of remote measurements for identifying a substance by its thermal characteristics using standard telecommunication fibers. This study also includes examining dynamic systems with changing phases of matter using fully fiber-optic technologies. Method. The hot wire method with fiber optic elements is employed in this study. The creation of the heating area was realized by forming the structure of the taper in the optical fiber, and for measurements, a fiber Bragg grating, which acts as a temperature sensor, was formed. Main results. In this study, what we believe to be a novel scientific and technical solution was developed to create a fiber-optic-sensitive element for identifying a substance by its thermal characteristics. The experiments were conducted using six samples with a specific heat capacity ranging from 1.0 to 4.2 kJ/(kg K). Based on the results, the dependences of the spectral shift of the resonance of the fiber Bragg grating on the values of the specific heat capacities of substances were plotted, and the maximum standard deviation was 0.0088 nm. The results of identifying the phase of a gas-liquid mixture in a flow are also presented. Practical significance. The results of the study are of scientific interest to researchers in areas requiring the analysis of samples with different thermal characteristics, determining the phase change in a flow, detecting the presence of impurities in the flows of known substances, measuring the level of liquids, etc.

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