# How fluent calculate heat-transfer-coefficient?

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 September 9, 2013, 14:57 How fluent calculate heat-transfer-coefficient? #1 Member   Join Date: Oct 2012 Posts: 44 Rep Power: 4 Hi, I have a simple test, a cube 1*1*0,2 (l*l*x). Boundary condition T1=350°K in upper face, T2=300°k in opposite face, k=200. So Q=k/x*A*(T1-T2)=50000 Fluent report flux no problem, Q=50000 as formula, but I want to export heat-transfer-coefficient for every cells. he must be 1000, but fluent calculate 1.2194E+003. Why? For this case I insert only 1 cell mesh.

 September 9, 2013, 17:29 #2 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,914 Blog Entries: 6 Rep Power: 38 what is the bulk velocity?

September 9, 2013, 17:55
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 Originally Posted by Far what is the bulk velocity?
Why bulk velocity?
it's a simple Heat transfer in a solid plate.

 September 9, 2013, 18:04 #4 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,914 Blog Entries: 6 Rep Power: 38 you want to check the thermal conductivity? Heat transfer coefficient is for the convection.

September 9, 2013, 18:20
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 Originally Posted by Far you want to check the thermal conductivity? Heat transfer coefficient is for the convection.
Goal is , that is conductance

 September 9, 2013, 18:44 #6 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,914 Blog Entries: 6 Rep Power: 38 isnt it obvious? As k is fixed and so is the dx

September 10, 2013, 03:12
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 Originally Posted by Far isnt it obvious? As k is fixed and so is the dx
Yes, in simple case. But when I have a complex structure whit fins?
Goal is to understand how fluent calculate this rate or I can calculate this from ''fluent-export''. So I can tell: this is average of structure from report flux. That is report flux=Q, U=Q/A/(T1-T2).
From mesh I can calculate every single Q(i) by cells, so I can compare average with single station to see the difference and if this difference is high.
Imagine a structure like this:

 September 10, 2013, 03:40 #8 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,914 Blog Entries: 6 Rep Power: 38 Delta X is changing ? K is changing? If yes then you UDF.

September 10, 2013, 03:47
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 Originally Posted by Far Delta X is changing ? K is changing? If yes then you UDF.
Only Delta x, k is constant.
how can I proceed?

September 18, 2013, 10:55
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 Originally Posted by Far Delta X is changing ? K is changing? If yes then you UDF.
In report fluent I have Heat Flow [ Watt ] (Heat Rate), that is Q for every face mesh that I call Qi, and area of mesh Ai. Whit delta Temperature I have U.
U=Qi/(Ai*delta(T))

How can I calculate this division?

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