Transient quenching heat transfer of high-temperature single-rod and two-rod configurations in water and saltwater: Effects of subcooling, salt concentration, and rod interaction

Transient quenching heat transfer of high-temperature rod configurations in water and saltwater plays a pivotal role in emergency cooling of high-temperature components. This study systematically investigates the quenching behavior of single- and two-rod configurations of stainless steel at high-temperatures, focusing on the effects of liquid subcooling, salt concentration, and rod-to-rod interaction under simplified two-rod configurations. Cylindrical rods heated to approximately 800 °C are rapidly immersed into quenching pools under controlled thermal and geometric conditions. Transient temperature histories measured at the rod centerline are used to reconstruct surface temperature, heat flux, and critical heat flux (CHF) through inverse heat conduction analysis, complemented by high-speed visualization of boiling behavior. Results show that quenching consistently proceeds through four reproducible regimes: film boiling, transition boiling, nucleate boiling, and natural convection. Increased liquid subcooling accelerates vapor condensation, destabilizes the vapor film, and shortens or suppresses the film boiling regime, enhancing cooling performance. For pure water, as the liquid subcooling increases from 0 to 50 °C, CHF increases from 572 to 1820 kW/m 2 , while the Leidenfrost temperature increases from approximately 302 to 586 °C. For saltwater at a pool temperature of 50 °C, CHF further increases from 1820 to 5687 kW/m 2 as the salt concentration increases from 0% to 15%. Saltwater further destabilizes the vapor film and suppresses stable film boiling by modifying interfacial boiling dynamics and elevating the Leidenfrost temperature, particularly under saturated and mildly subcooled conditions, resulting in a significant enhancement of CHF under the present conditions. Two-rod experiments demonstrate that small rod gaps delay rewetting owing to vapor accumulation, whereas larger gaps facilitate vapor removal and enhance quenching effectiveness. Overall, this study provides an experimentally validated basis for isolating fundamental thermal, interfacial, and geometric mechanisms governing transient quenching, supporting transient-aware assessment and providing benchmark experimental data for future research on modeling emergency cooling performance in high-temperature thermal systems under controlled and simplified conditions.