# Porous Media

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 November 14, 2005, 01:03 Porous Media #1 Jorge Guest   Posts: n/a 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

 November 15, 2005, 10:14 Re: Porous Media #2 Esti Armendariz Guest   Posts: n/a 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!

 November 17, 2005, 00:48 Re: Porous Media #3 nirmal Guest   Posts: n/a Hello 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.

 November 17, 2005, 04:22 Re: Porous Media #4 Tushar Guest   Posts: n/a 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.

 November 17, 2005, 04:24 Re: Porous Media #5 Esti Armendariz Guest   Posts: n/a 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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