The Local Evaporation Flux Along the Interface of a Droplet

2009 ◽  
Author(s):  
Fei Duan
Keyword(s):  
Vapor Phase ◽  
Thermal Conduction ◽  
Thermocapillary Convection ◽  
Water Evaporation ◽  
Rate Theory ◽  
Statistical Rate Theory ◽  
Turbulent Transition ◽  
State Water ◽  
Evaporation Flux ◽  
Liquid And Vapor Phases

In steady-state water evaporation, the local evaporation flux is found uniform before the thermocapillary convection transition at the droplet. If the thermocapillary flow is present, the local evaporation flux becomes nonuniform as a result of effects of thermal conduction from liquid and vapor phases, thermocapillary convection at interface, or the viscous dissipation after the interfacial turbulent transition. The local vapor-phase pressures predicted from statistical rate theory become nonuniform after the thermocapillary convection transition. But, the average predicted pressure agrees with the measured vapor-phase pressure.

Prediction of the Saturation Pressure of Water From Non-Equilibrium Measurements

2007 ◽  
Author(s):  
Fei Duan ◽  
C. A. Ward
Keyword(s):  
Vapor Phase ◽  
Saturation Pressure ◽  
Rate Theory ◽  
Statistical Rate Theory ◽  
Equilibrium Evaporation ◽  
Phase Temperature ◽  
Evaporation Flux ◽  
Saturation Vapor ◽  
Phase Pressure ◽  
Non Equilibrium

Statistical rate theory (SRT) was applied to predict the saturation pressure of H2O based on the measurements of interfacial liquid-phase temperature, interfacial vapor-phase temperature, vapor-phase pressure, and average evaporation flux in non-equilibrium evaporation experiments. It is found that the predicted saturation pressure agrees with the Smithsonian Tables and Table given in the Handbook of Chemistry and Physics for water, H2O. SRT provides a new efficient method to determine the saturation-vapor pressure from a non-equilibrium precess.

Experimental Study on Water Evaporation Enhanced by Surface Heating

2010 ◽  
Author(s):  
Fei Duan
Keyword(s):  
Thermal Conduction ◽  
Flat Surface ◽  
Water Evaporation ◽  
Interfacial Flow ◽  
Liquid Temperature ◽  
Temperature Position ◽  
Dividing Surface ◽  
Stefan Condition ◽  
Evaporation Flux ◽  
Gibbs Dividing Surface

The average evaporation flux was significantly higher while water was heated at a flat surface by two aligned heating elements than that while the water surface was heated 5 mm below in the designed experiments under the similar conditions. The observation is contrary to the Stefan condition. A thermodynamic model is derived from the Gibbs dividing-surface approximation at a flat evaporating surface to demonstrate that an interfacial flow can enhance the evaporation by transporting energy from a high temperature position to a low temperature position. The measures showed that the interfacial liquid temperature was up to 6.9°C higher around the heating wires than that at the centerline between two heating wires as water was heated at the interface. The induced interfacial flow can transport the energy to maintain the evaporation by overtaking the negative thermal conduction to the interface globally.

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