Numerical investigation of thermal runaway prevention in styrene polymerization using a PCM(R-245fa)-enhanced cooling jacket

Farrokhfar Valizadeh Harzand

doi:10.53063/synsint.2025.54301

Farrokhfar Valizadeh Harzand ¹

¹ Chemical Engineering Department, University of Mohaghegh Ardabili, Ardabil, Iran

https://doi.org/10.53063/synsint.2025.54301

Abstract

Styrene polymerization is a highly exothermic free-radical process that is intrinsically prone to thermal runaway due to strong Arrhenius kinetics and autoacceleration effects. In this study, a novel passive thermal management strategy based on a phase change material (PCM)-equipped cooling jacket is numerically investigated for a tubular styrene polymerization reactor. A two-dimensional axisymmetric model of a plug-flow reactor with an annular cooling jacket containing a water–R-245fa PCM emulsion is developed and solved using COMSOL Multiphysics. The model couples laminar flow, species transport, reaction kinetics, heat transfer, and PCM phase change using an apparent heat capacity formulation. Styrene polymerization is represented by a lumped global reaction with temperature-dependent Arrhenius kinetics and a heat of polymerization of -70 kJ.mol^-1. The influence of PCM volumetric concentration (5–30%) on reactor temperature control, reaction rate evolution, and monomer conversion is systematically analyzed and compared with a conventional water-cooled jacket. The results show that pure water cooling fails to prevent thermal runaway, with reactor temperatures exceeding 200 °C within minutes. In contrast, PCM-enhanced cooling significantly improves thermal stability by absorbing reaction heat through latent heat effects. At PCM loadings of 20% and higher, the reactor temperature is effectively clamped near the PCM boiling point (~85 °C), completely suppressing runaway behavior and maintaining stable, high monomer conversion. The study demonstrates that nano- and emulsion-based PCM cooling jackets can provide a robust, passive, and inherently safer alternative to conventional cooling systems for highly exothermic polymerization reactors.

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Keywords: R-245fa (1,1,1,3,3-pentafluoropropane), Phase change material (PCM), Thermal runaway, Styrene polymerization, COMSOL Multiphysics

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