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Old   November 14, 2005, 00:03
Default Porous Media
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I have the following relation of pressure drop vs velocity for a tube bank of a heat exchanger in x coordinate: dP/X=-1.6909*v^2-0.0762*v . Do i have to assign to alphax1,alphax2,alphax3=-1.6909 or only alphax1 so alphax2,alphax3=0, same for betax1,betax2,betax3.

Thanks for your help
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Old   November 15, 2005, 09:14
Default Re: Porous Media
Esti Armendariz
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Hi there,

You've got a channel flow, so is clearly a case of orthotropic resistance. aphax=1.6909 in the flow direction betax=0.0762 in the flow direction

In the cross-flow direction (y and z), assign big numbers.

Good luck!
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Old   November 16, 2005, 23:48
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I am also modelling same type of case(shell and tube HX 1*2)i am using alfax=5.6 e4 betax=5.6e4 alfay=5.6e4betay=5.6e4 and alfaz=0.5 betaz =0.4. do these values seem to be right. please comment.
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Old   November 17, 2005, 03:22
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The relation which you have is non linear whereas alpha and beta appears in linear equiation. Ensure that the the LHS is a derivative, otherwise you need to differentiate the expression to get the correcto values of alpha and beta.

Secondly if alpha y and alpha z is zero means there is no resistance in y and z direction.
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Old   November 17, 2005, 03:24
Default Re: Porous Media
Esti Armendariz
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Hi there, Well, I'm not an expert on this, but again if it's a channel flow, and the flowing direction is on the z axis then you should be allright. Another issue is where did you get those values from, etc...

Best regards, Esti
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