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Max. Packing Limit & Volume Fraction in Circulating Fluidized Bed

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Old   May 4, 2016, 11:21
Default Max. Packing Limit & Volume Fraction in Circulating Fluidized Bed
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Bramantyo
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Hello there

I am currently trying to simulating circulating fluidized bed boiler with Eulerian-Eulerian multiphase method, in FLUENT 15.
I am using 4 phases in this simulation. 1 phase is air, and then the other 3 are sands with different diameter.

The details are given below:
-phase 1: air
-phase 2: sand, diameter 50 micro
-phase 3: sand, diameter 175 micro
-phase 4: sand, diameter 500 micro

So my questions:
1. What is the appropriate max packing limit value for each sand phase? I've read in the user guide that max packing limit value maybe higher than 0.63(default value) if there is more than 1 sand phase

2. In the Slip Velocity Specification Method in Mass-Flow Inlet Boundary for sand phase, there is an option: Volume Fraction. What is the meaning of this volume fraction option? Can we just input the mass flow rate differently for each of the sand phase without choosing the volume fraction option?

Any explanation will be really helpful!

Thanks
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Old   May 16, 2016, 13:31
Exclamation fuidized bed
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Hi Brams,

unfortunately I can not help you because I am a beginner in this kind of work, but I think you can help me if you don't mind .I am a student of 2nd year master, I'm working on fluent.16 software for the simulation of fluidization (without combustion or chemical reaction) this fluidized bed uses the olive pomace as particles and air as the fluidizing. I draw the geometry of the boiler and I did the mesh but I found a lot of trouble about modeling (in fluent models), I try to understand but really it's not easy), please if you don't mind help me with advice or paper that can help me to advance in my project. I tried with documentation of ansys but it is too detailed and
scattered.
thank you for any help
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Old   May 23, 2016, 18:07
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Jerry
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Hi Brams,

I have the same doubt. I am trying to simulate bidisperse system by using eulerian model. While I found the total volume fraction of two solid phases can be very large.

The maximum packing limit for each solid phase is set to 0.6 while the total volume fraction can be as high as 0.85 in the result. I checked fluent theory guide manual and calculated the maximum packing limit for binary system. The packing limit calculated from those equations is around 0.73.

Hope someone can help.
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circulating fluidized bed, eulerian multiphase model, eulerian-eulerian model, max. packing limit, volume fraction.

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