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Estimating Tmean in CFD post

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Old   September 18, 2015, 06:43
Default Estimating Tmean in CFD post
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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?

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Old   September 18, 2015, 07:58
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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.
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Old   September 18, 2015, 08:19
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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???????
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Old   September 18, 2015, 08:38
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The message is very clear.. You want to evaluate an area integral on a line ? There is no cross section, or any area.
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Old   September 18, 2015, 08:45
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So what I can do to evaluate Tm along this line ? No idea else?
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Old   September 18, 2015, 09:00
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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.
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Old   September 18, 2015, 09:05
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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
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Old   September 18, 2015, 09:56
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Quote:
Originally Posted by mariam.sara View Post
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
Then your location is whole your domain.
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Old   September 18, 2015, 10:45
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Quote:
Originally Posted by Antanas View Post
Then your location is whole your domain.
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
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Old   September 18, 2015, 12:41
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Quote:
Originally Posted by mariam.sara View Post
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?
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Old   September 18, 2015, 14:20
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Quote:
Originally Posted by Antanas View Post
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.
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Old   September 18, 2015, 15:25
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Quote:
Originally Posted by mariam.sara View Post
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.
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Old   September 19, 2015, 08:10
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Quote:
Originally Posted by Antanas View Post
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?
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Old   September 19, 2015, 12:42
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Quote:
Originally Posted by mariam.sara View Post
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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