Photothermal evaporation of the ferromagnetic nanofluid droplets under a magnetic field

The ferromagnetic nanofluid droplets evaporating on the photothermally heated substrate exhibits different behaviors when compared with the water droplets. This paper establishes a droplet evaporation model, where the simulation results of the mixed mode evaporation have a good agreement with the operated experiments. The residual mass and evaporation rate of the water droplets and ferromagnetic nanofluid droplets at different temperatures and light intensities are investigated, indicating that the magnetic particles have a promoting effect on the droplet evaporation. Afterwards, a periodic magnetic field has been installed, and variations in the temperature and velocity fields during droplet evaporation are explored. The magnetic field further promotes the droplet evaporation, which can be attributed to the deformation of the droplets induced by the periodicity of the magnetic field. The current study investigates the influence of the magnetic particles and a magnetic field on the evaporation of the heated droplets, providing a theoretical guidance for the application of electric heaters, cooling fluids and heat pipes.