Dynamic behavior and cooling performance of polymer aqueous solution droplets upon impact with a high-temperature solid surface under contact boiling conditions

• Water droplet utilization rate is only 19 %–26 % during single droplet collision. • Polymers suppress droplet splashing and hardly affect its thermal properties. • Increasing polymer concentration enhances the cooling effect of droplets. • The droplet utilization rate of 100 ppm PEO droplet reaches 45 %–51 %. • The droplet utilization rate of 700 ppm PEO droplet reaches 83 %–85 %. Sustained rapid surface cooling is critical for flame suppression and reignition prevention during fire accidents. Water mist, with its high specific heat capacity and latent heat of vaporization, is widely used to cool high-temperature surfaces. However, its application is constrained by limited firefighting water resources. Previous studies enhanced the heat transfer efficiency of water by incorporating surfactants, nanoparticles, or low-molecular-weight (low- MW ) polymers. However, they hardly studied the problem of low water utilization caused by droplet boiling and breakup during the cooling process. To address this problem, this study improved the rheological properties of droplets by adding high- MW polymers to water. We used high-speed cameras and infrared thermal imagers to investigate the dynamic behavior and cooling performance when droplets impacted surfaces under contact boiling conditions. We found that low-concentration polymer additives suppressed droplet breakup, and splashing, prolonging the droplet-surface contact time. The droplets retained specific heat and latent heat of vaporization comparable to those of water. Temperature data indicated that the extended contact time enhanced the heat absorption of droplets (1.6–2.7 times of water) and improved liquid utilization (2–4 times of water). Furthermore, this study analyzed the force dynamics during droplet deformation and established a quantitative relationship between the maximum spreading factor and Weber ( We ) and Reynolds ( Re ) numbers, providing a theory for heat transfer rate analysis. This study revealed the coupling mechanism between the dynamic deformation and heat transfer processes during droplet impact on the heated surface, providing a new direction for developing fire-extinguishing additives for water mist.