Evaporation time and vapor generation limit of a droplet on a hot surface

• Published in: International journal of heat and mass transfer 2021-07, Vol.173, p.121280, Article 121280
• Main Authors: Liu, Y., Monde, M., Mitsutake, Y., Tsubaki, K.
• Format: Article
• Language: English
• Subjects: Conduction heating; Conductive heat transfer; Droplets; Evaporation; Heat; Heat flux; High temperature; Homogeneous bubble nucleation; Hot surfaces; Minimum evaporation time; Nucleation; Thermodynamic properties; Two-dimensional analysis; Vapor generation limit; Visual observation; Water drops
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2021.121280

•Heat flux was analyzed during heat conduction regime after droplet contacted hot surface.•A two-dimensional solution for estimating surface heat flux was newly derived.•Surface heat fluxes at minimum evaporation time point for different materials were consistent within 20%.•A simple equation was developed to estimate surface heat flux at minimum evaporation time point.•Droplet behavior was much different whether homogeneous bubble nucleation condition was satisfied or not. The characteristic of heat flux was analyzed during the heat conduction regime after a water droplet deposited onto a hot surface at the temperature bringing the minimum evaporation time. A two-dimensional solution for estimating surface heat flux was newly derived, in place of the existing one-dimensional one, when a finite size of the liquid droplet suddenly contacted a high-temperature surface of a semi-infinite thick solid. The estimated surface heat fluxes at the minimum evaporation time point for several materials with different thermal properties were consistent within an uncertainty of 20%, although the corresponding surface temperatures for different materials were much different. In addition, a simple equation was developed to estimate the surface heat flux at the minimum evaporation time point, which was validated for the liquid subcooling of 70-80 K and the water droplet radius of 1.0-1.5 mm. Visual observation revealed that the characteristic of the droplet behavior on the hot surface was much different whether the homogeneous bubble nucleation condition was satisfied or not.