Calorimetric Monitoring of Exothermic Reactions by Distributed Acoustic Sensing

This Letter demonstrates the potential of low-frequency Distributed Acoustic Sensing (LF-DAS) for calorimetric monitoring of chemical reactions. Using 2-propanol-water mixing as an exothermic model reaction, we employ a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\phi$</tex-math></inline-formula>-OTDR DAS system to quantify heat release with spatio-temporal resolution. The fiber-optic system captures thermally induced phase shifts of the narrowband laser, enabling quantitative heat release analysis with high agreement to theory. The presented calibration enables relating optical phase changes to temperature variation. Experimental results show the DAS system's ability to identify thermal hotspots and provide real-time insights into reaction dynamics. This work addresses key challenges in hotspot detection, introduces a novel approach for safe, efficient process control, and highlights the potential of LF-DAS for advanced calorimetric monitoring of large-scale exothermic (reactor) systems.