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Porous domain:Interfacial area density and heat transfer coefficient

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Old   September 7, 2012, 05:22
Default Porous domain:Interfacial area density and heat transfer coefficient
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Hello, I'm building a model for a cure of a composite material with CFX. The exact process that I'm simulating is a pultrusion. I have an heated steel die with a fiberglass-epoxy resin composite that proceed at a low speed in the die to be heated. I have modeled the composite material with a "Porous domain" where there is a fluid (epoxy-resin) and a solid (fiberglass). When I define the porous domain, under the "Porosity settings tab" the model ask for the "Interfacial area density" and the "heat transfer coefficient" between the fluid and solid parts. I have read the cfx pre user's guide, solver theory guide and solver modeling guide founding a few information about how to assign these values.
These are my 2 questions:
1)For the interfacial area density, I have read that it is the area of contact between the two phases in the porous domain for an unit volume (A/V). If I have the volume fiber fraction of my composite (Vf=0.639) and the composite diameter (it is a rod, D=0.0025 m) and the circumference of a single continous fiber (8.17*10^-5 m), can I calculate the "Interfacial area density" value specifying the area of contact between the resin and the total number of fibre contained in a unit volume of composite (I obtain a value about 98000m^2/m^3)?
2) Fiberglass and epoxy resin that I have as phases in my composite are both continue and for the heat transfer coefficient to specify in "Porosity settings tab" the guide refers to an inhomogeneous interphase heat transfer models in the "Solver theory guide". Reading this section I can find three models: "Particle model correlations" (for one continue phase and one dispersed phase, not my case), "Mixture models correlations" (for two continue phases, this is my case)and the "Two resistance model". Reading the "Mixture models correlations", the Solver theory guide refers to the "Mixture model correlations for Overall Heat Transfer Coefficient" in Solver Modeling Guide and here, to finally calculate the heat tranfer coefficient, refer to the previous paragraph "Particle Model Correlations for overall heat transfer coefficient ": the problem is that here to calculate the heat transfer, it refers to a dispersed particle that moves in a fluid (So it calculates "h" through Nusselt, Reynolds and Prandtl, that have a sense with a fluid, but not with a solid phase)! How I can do to calculate this heat tranfer coefficient?

Thank for the patience
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Old   September 9, 2012, 11:34
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Quote:
Originally Posted by l.te View Post
Hello, I'm building a model for a cure of a composite material with CFX. The exact process that I'm simulating is a pultrusion. I have an heated steel die with a fiberglass-epoxy resin composite that proceed at a low speed in the die to be heated. I have modeled the composite material with a "Porous domain" where there is a fluid (epoxy-resin) and a solid (fiberglass). When I define the porous domain, under the "Porosity settings tab" the model ask for the "Interfacial area density" and the "heat transfer coefficient" between the fluid and solid parts. I have read the cfx pre user's guide, solver theory guide and solver modeling guide founding a few information about how to assign these values.
These are my 2 questions:
1)For the interfacial area density, I have read that it is the area of contact between the two phases in the porous domain for an unit volume (A/V). If I have the volume fiber fraction of my composite (Vf=0.639) and the composite diameter (it is a rod, D=0.0025 m) and the circumference of a single continous fiber (8.17*10^-5 m), can I calculate the "Interfacial area density" value specifying the area of contact between the resin and the total number of fibre contained in a unit volume of composite (I obtain a value about 98000m^2/m^3)?
2) Fiberglass and epoxy resin that I have as phases in my composite are both continue and for the heat transfer coefficient to specify in "Porosity settings tab" the guide refers to an inhomogeneous interphase heat transfer models in the "Solver theory guide". Reading this section I can find three models: "Particle model correlations" (for one continue phase and one dispersed phase, not my case), "Mixture models correlations" (for two continue phases, this is my case)and the "Two resistance model". Reading the "Mixture models correlations", the Solver theory guide refers to the "Mixture model correlations for Overall Heat Transfer Coefficient" in Solver Modeling Guide and here, to finally calculate the heat tranfer coefficient, refer to the previous paragraph "Particle Model Correlations for overall heat transfer coefficient ": the problem is that here to calculate the heat transfer, it refers to a dispersed particle that moves in a fluid (So it calculates "h" through Nusselt, Reynolds and Prandtl, that have a sense with a fluid, but not with a solid phase)! How I can do to calculate this heat tranfer coefficient?

Thank for the patience
Hello, can anyone help me, please?
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Old   May 17, 2014, 23:45
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Evan Oscar Smith
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Hey I.te,

Did you ever solve this problem?
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