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panneerselvam.R July 8, 2005 08:39

mass transfer by source
 
hai all,

I have one question about setting additional variable mass transfer in CFX5.7.1.

in two phase (gas and water), There is a soluble component (A) in gas phase. I want to model the mass transfer of A from gas to water and I set two additional variables for A in each phase

Assuming: source=density*mass transfer coefficient *(saturation mass fraction of A in water- actual mass fraction of A in water), in which saturation mass fraction of A in water can be calculated by Herry's law.these source term gives unit of Kgm^-2s^-1 but when I input this source term in fluid mass source in cfx pre by using subdomain,but it giving error of it is not correct unit and required unit is Kgm^-3s^-1 of source

actualy in source term , i have to include the interfacial area, then only unit will match, but in cfx validate report of bubble column shows,cfx 5 take interfacial area automatically, but i don't know why this error is coming

please help my proplem

JP July 8, 2005 18:56

Re: mass transfer by source
 
Hi,

I am not sure how it works to define source in subdomain for your problem. But for species mass transfer in multiphase problem, you can define a transfer flux instead of total source. This is the approach that was used in the validation report you mentioned.

For example, for O2 component transfer in that report, the flux of interface mass transfer is : N=K(C*-C) where N = the flux across the films between gas and water kg/m2-s; C = liquid phase concentration kg /m3; K = liquid-phase transfer coefficient, m/s; C*= saturation liquid phase concentration, kg/m3;

Search 'Interphase Additional Variable Transfer Models' or 'transfer flux' in help files, you may find more details about this.

Regards

JP

panneerselvam.R July 9, 2005 03:21

Re: mass transfer by source
 
hai JB thanks for replying immeaditely,now i given source term in interfaces flux between addtional variables interphase transfer instead of creating subdomain,

thanks panneerselvam.R

panneerselvam.R July 9, 2005 12:03

Re: mass transfer by source
 
hai,

when i was run simulation of mass transfer between two phase using addtional variables interphase mass transfer ,i am getting following error

ERROR #001100279 has occurred in subroutine ErrAction. Message: Floating point exception: Type Unknown

Details of error:- ---------------- Error detected by routine POPDIR

CRESLT = ILEG

i couldn't find what type of error, please help me

with regards panneerselvam.R


test July 11, 2005 00:30

Re: mass transfer by source
 
Hi,

This means that your problem has crashed. If this error has occured within the first few iterations, it is probably because your wrong prolem setup/boundary conditions or you are using too large time step (least possible cause).

Check your definition of mass transfer source again and your boundary conditions

Regards, test


panneerselvam.R July 11, 2005 11:04

Re: mass transfer by source
 
hai,

now i am giving time step of 0.1 sec, this error is occurs at time step of 4.4 sec,anyway i will reduce the time step and run it

thanks

panneerselvam.R

panneerselvam.R July 12, 2005 08:46

Re: mass transfer by source
 
hai,

while i reduce the time step of 0.01 sec , i am getting same error at time of 3.6 sec , i don't know how do i solve it,please help me

thanks

panneerselvam.r

JP July 12, 2005 10:07

Re: mass transfer by source
 
It's difficult to judge the reason by limited information you provided. If you like, you can post your ccl file here or send to me by email.

Regards!

JP


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