Direct-contact heat transfer of single droplets in dispersed flow film boiling: Experiment and model assessment

Direct-contact heat transfer of a single saturated droplet upon colliding with a heated wall in the regime of film boiling was experimentally investigated using high-resolution infrared thermometry technique. This technique provides transient local wall heat flux distributions during the entire collision period. In addition, various physical parameters relevant to the mechanistic modelling of these phenomena can be measured. The obtained results show that when single droplets dynamically collide with a heated surface during film boiling above the Leidenfrost point temperature, typically determined by droplet collision dynamics without considering thermal interactions, small spots of high heat flux due to localized wetting during the collision appear as increasing We(n). A systematic comparison revealed that existing theoretical models do not consider these observed physical phenomena and have lacks in accurately predicting the amount of direct-contact heat transfer. The necessity of developing an improved model to account for the effects of local wetting during the direct-contact heat transfer process is emphasized. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC.

Automated summary

Experimental investigation was conducted on direct-contact heat transfer of a single saturated droplet colliding with a heated wall in the regime of film boiling, revealing the inadequacy of existing theoretical models in accurately predicting the heat transfer. Therefore, the necessity of developing an improved model to account for the effects of local wetting during the direct-contact heat transfer process is emphasized.