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Heat exchanger with wood pellets inside

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Old   February 10, 2019, 04:55
Default Heat exchanger with wood pellets inside
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Marcin
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Hello
I have a rare problem to solve
This is heat exchager wit heating process of wood pellet.
I need to model a heat transfer over wood pellet (little granular shapes inside smaller tube .
Can anyone help me to define wood pellet
Have anyone sugestions about this problem ??
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Old   February 10, 2019, 06:40
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How to model this depends on what you want to do.

The simplest approach is to use a heat source term to generate some heat.

More complex approaches model combustion chemistry, or the heating up process of the solid before it burns, or the mixture of gasses in the smoke.

So it depends on what you are trying to achieve with the model. Be aware that any of the more complex approaches I describe make the simulation MUCH more complex and are not areas beginners should consider doing.
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Old   February 10, 2019, 08:46
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Thanks Ghorrocks for answer

So I need to determinate a temperature of wood pellets on out.
this is continous process with constant pellet movement.
In the middle tube is only hot gas not combustion gasses.
I need to heat up this pellet with efficient heat exchanger
How to define pellet if this is granular medium wit non regular shape

Do U have any suggestion to simplify this process ??
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Old   February 10, 2019, 18:01
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I have a bit of an idea of what you are trying to do now, but still the approach to use depends on what you are trying to do.

What do you know about the physics of the heating of the wood pellets? Is it simple heating? Or is there chemistry you need to account for? Or water and other volatiles boiling off?

And on a larger scale - are you looking to model the entire process, and modelling the wood pellets as some type of lumped quantity or continuum is ok (eg porous body, fluidised bed or lagrangian particles) .. OR .. do you want detailed knowledge about the thermal profile in each individual pellet?
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Old   February 11, 2019, 02:12
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Hello Ghorrocks
I need to determinate average temperature on The cross section of The pellet mass (not single granular).
Yes on The process we have water product and gas is emitted from The wood.
But on The First simulation i want to skip all these phenomenas (water, emitted gaz from The wood). I want to make Heat transfer from ideal air gas to wood.
And general question is to how model wood pellets in my situation.
Sorry for my english
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Old   February 11, 2019, 06:05
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It depends on the details of what you are modelling.

I will eave it up to you from here:
You could use:
A eularian/eularian model, maybe with a fluidised bed model, maybe just a dispersed solid with a maximum packing fraction. This would be particularly good if the wood moves around a little.

A porous body model for the timber

Lagrangian particle tracking - but you will have to do some fancy footwork to get the motion realistic. You could define an initial location and define a user drag routine to make the particles follow a fixed path.
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Old   February 11, 2019, 06:20
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Thank U very much for The answer
I try Ur suggestions and i give feedback
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