Work

Heat flux reconstruction in droplet impact experiments using infrared thermography through sapphire

Year: 2025

Type: article

Abstract: Spray cooling is widely used for thermal management in applications requiring the dissipation of high heat fluxes. However, the underlying heat transfer mechanisms, particularly during individual droplet impacts, remain only partially understood. To investigate these complex phenomena, simplified experimental setups focusing on single droplet impacts are essential, as they enable detailed observation of key physical processes and accurate quantification of wall heat transfer.Infrared thermography through a sapphire substrate is a powerful technique for characterizing heat transfer at the droplet scale. When an emissive coating is applied to the upper surface of the sapphire, exposed to droplet impacts, this method enables time- and space-resolved thermal measurements. However, sapphire's intrinsic infrared emission and partial absorption can significantly interfere with the signal emitted by the surface coating, potentially leading to substantial overestimations of surface temperature and heat flux.This study presents and evaluates several correction methods to mitigate these effects, based on a series of droplet impact experiments conducted over a temperature range of 80 °C to 300 °C. A particularly effective approach combines thermal quadrupole methods with sine transforms of the surface temperature maps to reconstruct both the internal temperature distribution within the sapphire and the surface heat flux. This method is computationally efficient and straightforward to implement.Overall, the results highlight the critical importance of accounting for sapphire emission in infrared-based heat flux measurements and provide practical guidance for selecting appropriate correction strategies under varying droplet impact conditions.

Source: International Journal of Heat and Mass Transfer

DOI: 10.1016/j.ijheatmasstransfer.2025.128069

Authors: T. Potaufeux, O. Caballina, T. Czerwiec, G. Castanet

Institutions: Laboratoire Énergies & Mécanique Théorique et Appliquée, Université de Lorraine, Centre National de la Recherche Scientifique, Institut Jean Lamour

Language: English

Topic: Fluid Dynamics and Heat Transfer

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,220

Funder: Agence Nationale de la Recherche