Experimental and numerical investigation of flame temperature reduction in CO ₂ -diluted propane (R-290) mixtures for flammability mitigation

Environmentally friendly alternatives to conventional high–GWP refrigerants are being extensively explored worldwide. Among the natural refrigerants, propane (R290) has emerged as a promising candidate due to its excellent thermodynamic performance and zero ozone depletion potential. However, its high flammability poses a major safety concern, particularly under accidental leakage conditions that can lead to ignition. To mitigate this risk, this study investigates the influence of CO 2 dilution (0–30%) on the flame temperature of propane using a combination of COMSOL Multiphysics simulations and controlled experimental measurements. The primary objective is to quantify the reduction in maximum flame temperature as a function of CO 2 concentration in propane–CO 2 mixtures. The numerical model developed in COMSOL was validated against experimentally measured temperature profiles, demonstrating strong agreement. Results indicate that increasing CO 2 concentration from 0% to 30% reduces the peak flame temperature from 2094 K to 1654 K in experiments, and from 2410 K to 2190 K in simulations. This reduction is attributed to the high specific heat capacity and chemical inertness of CO 2 , which collectively suppress combustion intensity. The findings highlight the potential of CO 2 -propane mixtures as next-generation, low-GWP refrigerants with significantly reduced fire hazards, offering valuable insights for the design of safer and environmentally sustainable refrigerant blends.