Experimental investigation of cooling and heat soak-back in inclined jet impingement liquid film

Liquid film cooling plays a critical role in protecting the combustion chambers of liquid rocket engines from extreme thermal conditions. However, the heat soak-back effect remains a primary cause of engine overheating. This paper experimentally investigates the heat transfer characteristics during liquid film cooling and heat soak-back. The liquid film flow is visualized using a high-speed camera. The effects of liquid temperature, wall superheat, and input power are considered. The results indicate that the wall superheat exerts the strongest effect on the propagation of the wetting front, followed by liquid temperature and input power. The hindering effect of boiling decelerates the wetting front velocity. Thermal analysis reveals that the surface heat flux during liquid film cooling and heat soak-back exhibits a positive correlation with wall superheat and input power while being inversely proportional to liquid temperature. In addition, compared to the downstream of the liquid film, the wall temperature rise caused by the heat soak-back effect is more severe at the impingement point. Prolonged cooling durations amplify this divergence, with impingement point temperatures rising continuously while downstream of the liquid film exhibits sustained cooling. This is attributed to the combined effects of oblique jet impinging and the wall heat flux provided by the heater. The quantitative evaluation of cooling performance incorporates both the total heat removal and cooling efficiency. The cooling efficiency calculated through liquid film splashing rate demonstrates the coupling effect of liquid film flow and heat transfer.