Evaluation of gel foam stability under different heat transfer environments: An experimental study

• Gel foam thermal stability is precisely tuned by controlling liquid film viscosity. • Heat transfer modes induce distinct foam behaviors (drainage/expansion) • Conduction triggers sustained foam expansion via secondary foaming. • Convection dominates gel foam destabilization in heat transfer coupling conditions. Gel foam shows promising application prospects in firefighting, yet the effects of external heat transfer on its stability remain unclear. This study investigated the influence of liquid film viscosity on thermal stability of foam under different heat transfer modes, and clarified the stabilizing mechanism of high viscosity. The effects of external thermal environmental factors on gel foam stability was further studied, and the key factors in radiation-convection-conduction multi-field coupling environment were quantitatively analyzed by multivariate orthogonal experiments. Results show that increasing liquid film viscosity significantly strengthens foam stability: when viscosity increased from below 300 mPa·s to 1967 mPa·s, the foam stability time under thermal radiation extended from 40 min to over 180 min, drainage rate decreased from over 60% to nearly zero, and evaporation rate was substantially reduced. The external thermal environment significantly influences gel foam behavior differently. Radiation intensity increased from 2 kW/m 2 to 14 kW/m 2 , the time for foam expansion to 14 cm sharply decreased from over 51 min to 9 min. In convection environment, increasing the temperature from 100°C to 300°C substantially raised the internal temperature rise and evaporation of foam, and caused the dry-wet foam interface to move downward. In conduction environment, the shear force from rising hot air continuously generated new foam. The coupling experiment indicated that radiation intensity had the weakest effect on gel foam stability, followed by conduction, with convection exerting the most substantial effect. These findings offer valuable experimental insights for the optimal selection and application of gel foam in firefighting scenarios.