Heat Transfer in Fluuent

praveen.jpk · September 11, 2009, 02:56

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.

srjp · September 11, 2009, 05:01

For the walls, did you specify the correct free stream temperature (that would be the temperature of any fluid outside the wall)?

praveen.jpk · September 11, 2009, 05:57

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.

ashishmgad · September 11, 2009, 06:57

just to add :
do check your reference values in the report

caesrinivas · September 11, 2009, 07:51

i have query on this issue.. we should compulsorily specify heat transfer co-efficient ....

srjp · September 11, 2009, 08:52

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.

September 11, 2009, 02:56	Heat Transfer in Fluuent	#1
praveen.jpk New Member Praveen Kumar Jagarlapudi Join Date: Sep 2009 Posts: 7 Rep Power: 16	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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September 11, 2009, 05:01		#2
srjp Member JP Join Date: Mar 2009 Posts: 57 Rep Power: 18	For the walls, did you specify the correct free stream temperature (that would be the temperature of any fluid outside the wall)?

September 11, 2009, 05:57		#3
praveen.jpk New Member Praveen Kumar Jagarlapudi Join Date: Sep 2009 Posts: 7 Rep Power: 16	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.

September 11, 2009, 06:57		#4
ashishmgad New Member Ashu Join Date: Mar 2009 Posts: 7 Rep Power: 17	just to add : do check your reference values in the report

September 11, 2009, 07:51		#5
caesrinivas New Member srini Join Date: Jul 2009 Posts: 7 Rep Power: 16	i have query on this issue.. we should compulsorily specify heat transfer co-efficient ....

September 11, 2009, 08:52		#6
srjp Member JP Join Date: Mar 2009 Posts: 57 Rep Power: 18	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.