Effects of fluid properties on flow and heat transfer of a liquid film formed by inclined jet impingement

This study investigates the flow and heat transfer characteristics of the liquid film formed by fluid with different physical properties (surface tension and viscosity) on the heated surface. The regulation of fluid properties is achieved by the combined use of glycerol and two surfactants with distinct mechanisms. The liquid film flow is visualized using a high-speed camera. The temperature change during the liquid film cooling is measured using a thermocouple, and the surface heat flux is obtained by combining the inverse heat transfer algorithm. Results demonstrate that increased liquid viscosity suppresses surface wave amplitude and reduces liquid film coverage, while decreased surface tension diminishes interfacial stability, weakening the hydraulic jump characteristics. In addition, lower surface tension enhances bubble nucleation density in the boiling zone. Bubble cluster compresses liquid in wetting regions, inducing inward liquid accumulation. Subsequent bubble collapse creates a transient dry patch, leading to the formation of wavy film edges. Heat transfer analysis confirms that bubble clusters form a structure similar to a vapor film, reducing heat flux at wetting fronts by 9%–13.7%. Simultaneously, higher viscosity decreases effective cooling area, resulting in 12.6%–34.8% heat flux reduction across different zones. A dimensionless correlation between maximum heat flux and fluid parameters is established; the correlation exponents quantitatively validate the dominant influence of viscosity and surface tension on heat transfer performance.