The Mushy Zone in a Phase Change Model of a Semitransparent Material With Internal Radiative Transfer

1988 ◽  
Vol 110 (1) ◽  
pp. 260-263 ◽  
Author(s):  
S. H. Chan ◽  
K. Y. Hsu
Keyword(s):  
Radiative Transfer ◽  
Mushy Zone ◽  
Phase Change ◽  
Change Model ◽  
Semitransparent Material

scholarly journals Sensitivity of Numerical Predictions to the Permeability Coefficient in Simulations of Melting and Solidification Using the Enthalpy-Porosity Method

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4360 ◽  
Author(s):  
Amin Ebrahimi ◽  
Chris R. Kleijn ◽  
Ian M. Richardson
Keyword(s):  
Mushy Zone ◽  
Phase Change ◽  
Permeability Coefficient ◽  
Numerical Predictions ◽  
Fluid Velocities ◽  
Increased Sensitivity ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
High Degree ◽  
Melting And Solidification

The high degree of uncertainty and conflicting literature data on the value of the permeability coefficient (also known as the mushy zone constant), which aims to dampen fluid velocities in the mushy zone and suppress them in solid regions, is a critical drawback when using the fixed-grid enthalpy-porosity technique for modelling non-isothermal phase-change processes. In the present study, the sensitivity of numerical predictions to the value of this coefficient was scrutinised. Using finite-volume based numerical simulations of isothermal and non-isothermal melting and solidification problems, the causes of increased sensitivity were identified. It was found that depending on the mushy-zone thickness and the velocity field, the solid–liquid interface morphology and the rate of phase-change are sensitive to the permeability coefficient. It is demonstrated that numerical predictions of an isothermal phase-change problem are independent of the permeability coefficient for sufficiently fine meshes. It is also shown that sensitivity to the choice of permeability coefficient can be assessed by means of an appropriately defined Péclet number.

Numerical Simulation of Melting in Metal Foam/Paraffin Composite Phase Change Material Using a Physically More Reasonable Macroscale Model

2019 ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Metal Foam ◽  
Phase Interface ◽  
Change Model ◽  
Composite Phase Change Material ◽  
Convection Dominated ◽  
Change Material ◽  
Change Problem

Abstract In this work, a macroscale model for melting phase change of metal foam/paraffin composite phase change material (MFPC) is developed by employing the enthalpy-porosity method and volume averaging technique. Both cases of varied and unvaried paraffin density during phase change are investigated in the model, and diffusion dominated interstitial heat exchange between paraffin and metal foam is considered along with the convection dominated interstitial heat transfer. The visualization experiments on melting phase change of copper foam/paraffin composite are carried out to validate the developed phase change model. It is found that with consideration of varied density of paraffin, the developed model can effectively solve the real melting problem of MFPC when metal foam is initially filled with solid paraffin. If the Boussinesq approximation is employed (i.e., unvaried paraffin density is considered during phase change), the model is more appropriate for the phase change problem on condition that metal foam can just be filled with liquid paraffin in the end of the melting process. Hence according to different treatments of paraffin density, the application of the phase change model needs to consider the influence of real paraffin filling condition of MFPC. The phase change model considering diffusion dominated interstitial heat transfer between stationary paraffin and metal foam can more accurately capture the solid-liquid phase interface positions as compared with the model only considering the convection dominated interstitial heat transfer. The present study can provide guidance for physically more reasonable simulation of the practical phase change problem of MFPC.

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