HEAT TRANSFER AND NON-EQUILIBRIUM PHASE CHANGE OF LAMELLAE UNDER PLASMA SPRAY CONDITIONS

2007 ◽  
Vol 11 (2) ◽  
pp. 191-204 ◽  
Author(s):  
Y. Lahmar-Mebdoua ◽  
Armelle Vardelle ◽  
Pierre Fauchais ◽  
Dominique Gobin
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Plasma Spray ◽  
Equilibrium Phase ◽  
Non Equilibrium

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

Macroscale modeling of solid-liquid phase change in metal foam/paraffin composite: Effects of paraffin density treatment, thermal dispersion and interstitial heat transfer

2020 ◽  
pp. 1-32
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Phase Change ◽  
Equilibrium Model ◽  
Metal Foam ◽  
Thermal Dispersion ◽  
Dispersion Effect ◽  
Solid Paraffin ◽  
Solid Liquid ◽  
Non Equilibrium

Abstract This work focuses on macroscale modeling of solid-liquid phase change in metal foam/paraffin composite (MFPC), addressing the treatment of paraffin density (under distinct paraffin filling conditions in metal foam), thermal dispersion effect and influence of thermal diffusion dominated interstitial heat transfer. To this end, a macroscale thermal non-equilibrium model for melting in MFPC with fluid convection is developed by employing the enthalpy-porosity technique and volume averaging approach. Meanwhile, visualized experiments on melting of MFPC sample are carried out to validate the modeling results. Comparing the numerical modeling and experimental visualization results, it is found that for MFPC with an initially saturated filling condition in metal foam using solid paraffin, the varied paraffin density is preferred to be employed for developing accurate phase change model. However, for MFPC that can be just filled with liquid paraffin after melting (i.e., non-saturated filling condition using solid paraffin), Boussinesq approximation is preferred to achieve satisfying phase change simulation. Thermal dispersion effect in MFPC is proved to be negligible, which should not be overvalued to avoid inducing physical distortions of heat transfer and fluid flow. Consideration of diffusion dominated interstitial heat transfer in the thermal non-equilibrium model is vital to accurately capture phase interface evolutions as well as to reasonably simulate the mushy zone of paraffin; and the model only incorporating the convection induced interstitial heat transfer will predict quite inaccurate phase change process. This study can provide useful guidance in macroscale modeling of phase change in MFPC.

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.

Numerical Analysis of Heat Transfer and Flow in a Passive Condensation Heat Exchanger

2013 ◽  
Author(s):  
Jong Chull Jo ◽  
Kyu Sik Do ◽  
Yong Kab Lee
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Fluid Model ◽  
Equilibrium Phase ◽  
Saturated Steam ◽  
Outer Side ◽  
Change Model ◽  
Mass Rate ◽  
Two Fluid Model

A PWR design incorporates a passive auxiliary feedwater system equipped with one passive condensation heat exchanger (PCHX) which consists of inclined V-shaped tube bundles submerged in a water pool of which the top is open to the atmosphere. During the PCHX operation, saturated steam flows into the PCHX where steam is condensed inside of the tubes by cooling the outer side with the pool water. Then, the condensate flows out passively by gravity. Because the thermal-hydraulic characteristics in the PCHX determine the condensation mass rate and the possibility of thermal stratification-induced fatigue of the pool tank wall, system instability and waterhammer, it is important to understand the phase change flow in the PCHX. In this paper, the complex phase change heat transfer and multi-phase flow in a PCHX tube model were numerically simulated. The single fluid multi-component flow model with the equilibrium phase change model was employed for the condensation phase change flow inside the tube and the two-fluid model with the wall boiling model and the equilibrium phase change model was used for the boiling-induced natural convection outside the tube in the pool. Based on the present numerical simulation, the characteristics of the heat transfer and flow in the PCHX are discussed and illustrated for some typical results.

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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