Spatial distribution of heat transfer coefficient in the vicinity of wetting front during falling liquid film cooling of a vertical hot wall

• Wall temperature distribution during quenching was measured by IR camera. • Spatial HTC distribution during quenching was derived experimentally. • Dimensionless correlation was developed for the HTC distribution. • Calculated wetting velocities agreed with the experimental data well. Spatial distribution of the heat transfer coefficient (HTC) in the vicinity of the wetting front is of crucial importance in predicting the wetting velocity during liquid film cooling of a high-temperature solid surface. However, mainly due to the lack of experimental data, no sufficiently reliable model has been developed so far for the HTC distribution in this fundamental thermal-hydraulic situation. In the present work, experiments using a high-speed infra-red camera were carried out to measure the transient of wall temperature distribution during wetting of a high-temperature vertical wall with a falling liquid film. Based on the HTC distributions calculated from the measured temperature data, dimensionless correlations were developed for the HTC distribution near the wetting front. It was confirmed that the propagation velocities of the wetting front (wetting velocity) calculated using the proposed correlations agree with the experimental data accumulated in this work well.