scholarly journals Analysis of Non-Equilibrium Phase Change in Transfers at Low Water Content by Considering the Film Flow

2021 ◽  
Vol 17 (1) ◽  
pp. 1-13
Author(s):  
Marcel Bawindsom Kébré ◽  
François Ouédraogo ◽  
Bétaboalé Naon ◽  
Fabien Cherblanc ◽  
François Zougmoré
Keyword(s):  
Phase Change ◽  
Water Content ◽  
Film Flow ◽  
Equilibrium Phase ◽  
Non Equilibrium

Non-Equilibrium Phase Change in a Proton Exchange Membrane Fuel Cell

2010 ◽  
Author(s):  
N. Khajeh-Hosseini-Dalasm ◽  
Kazuyoshi Fushinobu ◽  
Ken Okazaki
Keyword(s):  
Fuel Cell ◽  
Phase Change ◽  
Proton Exchange Membrane ◽  
Equilibrium Phase ◽  
Proton Exchange ◽  
Isothermal Model ◽  
Change Rate ◽  
Liquid Saturation ◽  
Exchange Membrane ◽  
Non Equilibrium

A three-dimensional steady-state two-phase non-isothermal model which couples the water and thermal management has been developed in order to numerically investigate the spatial distribution of the interfacial mass transfer phase-change rate in the cathode side of a proton exchange membrane fuel cell (PEMFC). A non-equilibrium evaporation-condensation phase change rate is incorporated in the model which allows a supersaturation and undersaturation take place. The differences of non-equilibrium phase and equilibrium assumption inside the gas diffusion layer (GDL) has been addressed by comparing the corresponding liquid saturation and temperature distributions. Regarding water management, the assumption of isothermal model versus the non-isothermal model has been investigated. A parametric study has been also carried out to investigate the effects of operation conditions namely as the channel inlet humidity, cell operating temperature and inlet mass flow rate on the phase-change rate. Since the exact values of the phase change constants for the hydrophobic GDL has not been specified yet, the effects of the phase-change constant on the liquid saturation distribution are demonstrated.

Non-Equilibrium Phase Change in Metal Induced by Nanosecond Pulsed Laser Irradiation

2001 ◽  
Vol 124 (2) ◽  
pp. 293-298 ◽  
Author(s):  
Xianfan Xu ◽  
David A. Willis
Keyword(s):  
Phase Change ◽  
Laser Irradiation ◽  
Rapid Heating ◽  
Equilibrium Phase ◽  
Saturation Pressure ◽  
Pulsed Laser ◽  
Superheated Liquid ◽  
Phase Explosion ◽  
Nanosecond Pulsed Laser ◽  
Non Equilibrium

Materials processing using high power pulsed lasers involves complex phenomena including rapid heating, superheating of the laser-melted material, rapid nucleation, and phase explosion. With a heating rate on the order of 109K/s or higher, the surface layer melted by laser irradiation can reach a temperature higher than the normal boiling point. On the other hand, the vapor pressure does not build up as fast and thus falls below the saturation pressure at the surface temperature, resulting in a superheated, metastable state. As the temperature of the melt approaches the thermodynamic critical point, the liquid undergoes a phase explosion that turns the melt into a mixture of liquid and vapor. This article describes heat transfer and phase change phenomena during nanosecond pulsed laser ablation of a metal, with an emphasis on phase explosion and non-equilibrium phase change. The time required for nucleation in a superheated liquid, which determines the time needed for phase explosion to occur, is also investigated from both theoretical and experimental viewpoints.

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