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March 23, 2012, 06:55 
Flux Problem at Inlet

#1 
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Piyush Sharma
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Location: India, Uttar Pradesh
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I am having a problem in giving the inlet boundary condition as i know only the flux at inlet, else everything like velocity, mass flow rate at inlet as well as on outlet are unknown and at the outlet there is a fan which is sucking the air from the inlet. Even pressure is also unknown at the inlet, else i can give the atmospheric pressure at the inlet.
Please help me out Thanks in advance. 

March 23, 2012, 14:35 

#2 
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banty
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Hi,
What flux u know at inlet ? U must have some more data (BC) otherwise u cant solve 

March 23, 2012, 15:03 

#3 
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Piyush Sharma
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we know only heat flux at the inlet.
for ex : lets say there is a pump at the outlet of a pipe and it is sucking the fluid from the inlet, so in this type of case we don't have either velocity and mass flow rate known at the inlet as well as pressure is also not the atmospheric. we need to convert the heat flux BC to the available BC, but i dont know how to convert these type of BC's to the available BC's given in Fluent. Thanks 

March 24, 2012, 03:37 

#4 
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banty
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I am not sure but probably u can apply Fan BC at outlet but u have to give some BC at inlet in term of velocity or pressure because u may not be solving energy equation for this problem.
What do u mean by convert heat flux BC to the available BC's given in Fluent. 

March 24, 2012, 04:35 

#5 
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Piyush Sharma
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convert heat flux BC to the available BC's given in Fluent : it means we can convert the given heat flux (w/m^2) to the heat generation (w/m^3) as we can have the option for solving with given heat generation rate with in the system.
But this theory works or not i am not sure about it. 

March 24, 2012, 04:44 

#6 
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banty
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probably u are trying to know the mass flow rate through outlet so why u are trying to solve energy equation for this problem.


March 24, 2012, 04:52 

#7 
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Piyush Sharma
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As we are also interested in knowing the temperature of the fluid at the outlet.
Actually a porous body is impinging with a known heat flux and simultaneously the fluid is also sucked by a fan. So, we dont have idea about velocity, mass flow rate at the inlet, and i want to know how much heat is carried away by the fluid from the solid portion of the porous block and this can only be solved by solving the energy equation. 

March 28, 2012, 13:36 

#8 
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banty
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Hello,
Any how u require sufficient BC either actual or guess value (for trial) to solve the Partial differential equation that what fluent does. 

March 28, 2012, 14:10 

#9 
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Piyush Sharma
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i think i have to use the trial and error method.


April 19, 2012, 02:57 

#10 
New Member

As you described, you can make expansion region both in inlet and outlet. according to supposeing model, BC set as belows:
expansion inlet: pressure inlet 0 expansion outlet: pressure outlet 0 fan:MRF model heat flux wall: interior with heat flux. Regards Guava 

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