Abstract: Addressing engineering problems such as thermal runaway protection in new energy batteries and fire suppression in ultra-high voltage substations, rapid cooling of high-temperature solid surfaces plays a pivotal role in hazard control. While water mist/spray demonstrates superior phase-change cooling capacity, droplet fragmentation and splashing induced by boiling and inertial impact substantially compromise its cooling efficiency. This study modulates droplet dynamics through the polyethylene oxide (PEO) additive (700×10-6) to enhance the cooling effect. Single-droplet impact experiments revealed distinct cooling mechanisms: At approximately 200 ℃, where stable vapor film formation was inhibited, PEO-containing droplets demonstrated enhanced surface adhesion and suppressed fragmentation, achieving up to 4.3 times greater temperature differential and 10% faster cooling rate compared to pure water. Conversely, at around 400 ℃, where stable vapor films developed, the improved droplet integrity of PEO solutions paradoxically reduced heat absorption capacity due to more effective vapor layer insulation. Spray cooling experiments further demonstrated that rheological modification could significantly enhance the cooling performance of water under contact boiling. This approach showed particular promise for improving the thermal runaway suppression in batteries during the early stages.

Key words: water-based fire extinguishing agent, PEO additives, cooling efficiency, droplet impact, high-temperature surfaces