- Author
-
diMarzo, M.
|
Evans, D. D.
- Title
- Evaporation of a Water Droplet Deposited on a Hot High Thermal Conductivity Solid Surface.
- Coporate
- Maryland Univ., College Park
National Bureau of Standards, Gaithersburg, MD
- Report
-
NBSIR 86-3384,
August 1986,
33 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
cooling
|
droplets
|
evaporation cooling
|
extinguishing
|
spray quenching
|
sprinkler systems
|
water sprays
|
thermal conductivity
- Abstract
- A model is presented that predicts major features of the evaporation of water droplets deposited on a hot non-porous solid surface. In the temperature range of interest, nucleate boiling heat transfer is fully suppressed, hence the model is only concerned with the evaporative process. In the model, the solid material is assumed to have high thermal conductivity and diffusivity, so that the surface temperature under the water droplet can be considered uniform. The temperature of this portion of a larger solid surface covered by the liquid is calculated from the classic solution for contact temperature between two semi-infinite bodies. The liquid-vapor interfacial temperature and the water-vapor molar fraction in the air at the exposed surface of the water droplet are deduced from the coupled heat and mass transfer energy balance at the interface. Spatial and temporal integration of the overall droplet energy equation is used to predict the droplet evaporation time and the instantaneous evaporation rate. Model predictions for the total evaporation time and temporal variation of the droplet volume agree well with experiments performed using a heated aluminum block. The model is used to quantify spacial and temporal heat fluxes distribution at the exposed surface of the water droplet.