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Old   September 11, 2009, 02:56
Default Heat Transfer in Fluuent
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Praveen Kumar Jagarlapudi
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Dear All,

I have a question in heat transfer model.

I am doing CFD analysis on Heat exchanger model , its like rectangular box having larger dimensions in length.

Boundary Conditions:

1) At Inlet: Inlet velocity (7.03 m/s) and temperature (1223K)
2) At Outlet: Pressure outlet (0 Pa) and temperature(443).

I run the model but i am not getting the result of reduced temperature from inlet to outlet. I specified the convection heat transfer coefficient ( h= 8.41 w/m^2 K).

How can i achieve my result like temperature gradient in the model. Please explain the procedure.
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Old   September 11, 2009, 05:01
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For the walls, did you specify the correct free stream temperature (that would be the temperature of any fluid outside the wall)?
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Old   September 11, 2009, 05:57
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Praveen Kumar Jagarlapudi
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Yes exactly i gave the same. Free stream temperature of 300K.

from inlet to outlet it is reducing only 30 K. I want to reduce 780 k.

If you share any procedure to do it will be more helpful for me.
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Old   September 11, 2009, 06:57
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Ashu
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just to add :
do check your reference values in the report
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Old   September 11, 2009, 07:51
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srini
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i have query on this issue.. we should compulsorily specify heat transfer co-efficient ....
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Old   September 11, 2009, 08:52
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You state that you want to see a drop of 780K in temperature. But did you check analytically whether such a drop is possible with the current settings? You can do simple energy balance calculations to see how much would be the drop.

If m = mass flow rate
Cp = specific heat capacity
U = Heat transfer coefficient
A = Surface area of the walls (through which convective heat transfer takes place)
T1 = inlet temp
T2 = outlet temp
Tave = (T1+T2)/2
To = Outside temp
If we neglect the wall thickness,

mCp(T1 - T2) = UA(Tave - To)

Using this, you can calculate your expected outlet temperature (T2). Fluent can only calculate based on the given conditions.
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