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Probing the temperature profile across a liquid-vapor interface upon phase change
1Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104, USA.
The Journal of Chemical Physics
|October 22, 2020
Summary
This study reveals that vapor temperature profiles near evaporating interfaces depend on heat flux. The temperature jump and gradient vary, impacting phase change predictions.
Area of Science:
- Thermodynamics
- Fluid Dynamics
- Materials Science
Background:
- Accurate prediction of evaporation, boiling, and condensation requires understanding liquid-vapor interface temperature profiles.
- Previous studies suggest an inverted temperature profile (lowest temperature at the interface), but this is not universally observed.
- Non-equilibrium thermodynamics and molecular dynamics simulations have been used to investigate this phenomenon.
Purpose of the Study:
- To systematically investigate the temperature profile across a liquid-vapor interface during phase change using non-equilibrium molecular dynamics (NEMD) simulations.
- To examine the influence of various heat fluxes on the temperature profile in a two-interface system (evaporating and condensing).
- To analyze the vapor temperature characteristics within the Knudsen layer and bulk vapor.
Main Methods:
- Non-equilibrium molecular dynamics (NEMD) simulations were employed.
- A two-interface system was simulated, featuring both evaporation and condensation.
- Systematic variation of applied heat fluxes was performed to observe their effects.
Main Results:
- The vapor temperature exhibits distinct behaviors within the Knudsen layer and the bulk vapor.
- Both the direction and magnitude of the vapor temperature gradient are dependent on the applied heat flux.
- The temperature jump at the liquid-vapor interface is also a function of the applied heat flux.
- Interfacial entropy generation rate during evaporation is positive, aligning with non-equilibrium thermodynamics predictions.
Conclusions:
- The temperature profile across a liquid-vapor interface during phase change is significantly influenced by heat flux.
- NEMD simulations provide valuable insights into the complex thermal phenomena at evaporating and condensing interfaces.
- The findings contribute to a more accurate understanding and prediction of phase change processes.
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