# Estimating Tmean in CFD post

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September 18, 2015, 06:43
Estimating Tmean in CFD post
#1
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Hello I attempt to estimate Tm using CFD post which defined as illustrated at the image may somebody guide me how can I write this expression in CFD post?

mariam
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 Tm.png (5.2 KB, 8 views)

 September 18, 2015, 07:58 #2 Senior Member   Join Date: Jun 2009 Posts: 592 Rep Power: 13 Your expression already assumes constant/uniform specific heat capacity, Cp. Therefore, you can use the standard CEL averaging functions. Since Cp cancels out, T_mean = massFlowAve(Temperature)@Locator The next step is to define the Locator of interest. Perhaps you define a cut plane through the geometry, and use it to evaluate the expression.

 September 18, 2015, 08:19 #3 Senior Member   Join Date: Jan 2011 Posts: 236 Rep Power: 9 Hello I draw a line through the geometry named it as Line 1 at section where x=0.7125 m from pipe inlet and wrote an expression as: Tm=massFlowAve(Temperature)@Line 1 but when I press evaluate it give me the error below: Error Only geometries with surface data are allowed for calculating massFlowAve what the problem???????

 September 18, 2015, 08:38 #4 Senior Member   Join Date: Jun 2009 Posts: 592 Rep Power: 13 The message is very clear.. You want to evaluate an area integral on a line ? There is no cross section, or any area.

 September 18, 2015, 08:45 #5 Senior Member   Join Date: Jan 2011 Posts: 236 Rep Power: 9 So what I can do to evaluate Tm along this line ? No idea else?

 September 18, 2015, 09:00 #6 Senior Member   Join Date: Jun 2009 Posts: 592 Rep Power: 13 I think you need to better describe what you are trying to achieve. The mean, ( or better known bulk) temperature is defined for a cross section of the flow and nothing else. What is your cross section of interest ? Perhaps you intend to plot the variation of the bulk temperature along a series of cross sections that follow some kind of line path. To start, I would do the manual work. Create the cross section of interest, evaluate T_mean, create another one downstream, evaluate and confirm you are in the right direction. Then, you try to automate, simplify the effort.

 September 18, 2015, 09:05 #7 Senior Member   Join Date: Jan 2011 Posts: 236 Rep Power: 9 Actually I am trying to evaluate Tm in order to estimate heat transfer coefficient from the relation: h=heat flux/(Twall-Tbulk) I have 2 D pipe geometry and want predict h at different axial locations I used Fluent for simulations just use CFD post for results

September 18, 2015, 09:56
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Quote:
 Originally Posted by mariam.sara Actually I am trying to evaluate Tm in order to estimate heat transfer coefficient from the relation: h=heat flux/(Twall-Tbulk) I have 2 D pipe geometry and want predict h at different axial locations I used Fluent for simulations just use CFD post for results

September 18, 2015, 10:45
#9
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Quote:
No you wrong I want to compare my results with experimental work in it h predicted at selected sections from the pipe so predicting for the whole domain incorrect

September 18, 2015, 12:41
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Quote:
 Originally Posted by mariam.sara No you wrong I want to compare my results with experimental work in it h predicted at selected sections from the pipe so predicting for the whole domain incorrect
And how they measured Tbulk?

September 18, 2015, 14:20
#11
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Quote:
 Originally Posted by Antanas And how they measured Tbulk?
They measured the bulk temperature at selected sections from the pipe currently I draw lines at these sections but do not know how to write expression in CFD post for it.

September 18, 2015, 15:25
#12
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Quote:
 Originally Posted by mariam.sara They measured the bulk temperature at selected sections from the pipe currently I draw lines at these sections but do not know how to write expression in CFD post for it.
Why line? Anyway you can use areaAve or lengthAve or as Opaque wrote massFlowAve.

September 19, 2015, 08:10
#13
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Quote:
 Originally Posted by Antanas Why line? Anyway you can use areaAve or lengthAve or as Opaque wrote massFlowAve.
Yes I tried Opaque suggestion with massFlowAve but it give me error as illustrated at my previous post?

September 19, 2015, 12:42
#14
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Quote:
 Originally Posted by mariam.sara Yes I tried Opaque suggestion with massFlowAve but it give me error as illustrated at my previous post?
You tried it at a line, but you should use section plane.

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