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malay October 29, 2012 08:06

heat transfer distribution
 
1 Attachment(s)
I have simulated problem , the base of channel is a heat transfer source ( constant ) , when i plot the total surface heat transfer flux at this section ( the base of the channel ) , its appear as a constant line exept at the end and beginning of the channel ?! i need sombody help me why this happen ??

http://www.cfd-online.com/Forums/att...on-vbvbvbv.jpg

malay October 30, 2012 00:08

can somebody get me some help ??

A7A October 30, 2012 01:04

Hi,

What is the type of BC you gave to the base of the channel, is it heat flux or temperature?

sofie1 October 30, 2012 01:38

Hi
Is your geometry 2D or 3D

malay October 30, 2012 01:40

Quote:

Originally Posted by sofie1 (Post 389218)
Hi
Is your geometry 2D or 3D

Thanks for reply ......

my geometry is 3D

malay October 30, 2012 01:41

Quote:

Originally Posted by A7A (Post 389217)
Hi,

What is the type of BC you gave to the base of the channel, is it heat flux or temperature?

thanks for reply .......

heat flux

A7A October 30, 2012 10:30

As the BC is heat flux, fluent will give you this result(constant heat flux), and if you want to check how the heat flux is changing along the channel base you have to use temperature as BC for the channel base.

malay October 30, 2012 10:32

Quote:

Originally Posted by A7A (Post 389297)
As the BC is heat flux, fluent will give you this result(constant heat flux), and if you want to check how the heat flux is changing along the channel base you have to use temperature as BC for the channel base.

but why there is jump in the end and the bedninig ??

A7A October 30, 2012 10:42

I dont know why fluent give this jump, but have you checked the temperature variation along the channel base, and the heat transfer coefficient. If there isnt any thing wrong so it maybe something related to the nature of the mesh you are using.

malay October 30, 2012 10:46

Quote:

Originally Posted by A7A (Post 389299)
I dont know why fluent give this jump, but have you checked the temperature variation along the channel base, and the heat transfer coefficient. If there isnt any thing wrong so it maybe something related to the nature of the mesh you are using.

the Tem distribution is ok but the Nu number dont go to standard ( 4.3 ) , Nu go to zero ??

A7A October 30, 2012 10:49

could you put a picture of temperature and Nu plots.

malay October 30, 2012 12:34

2 Attachment(s)
Quote:

Originally Posted by A7A (Post 389302)
could you put a picture of temperature and Nu plots.

i attached the pictures

A7A November 3, 2012 04:52

The temperature of the channel base is decreasing, so Nu number must be increasing along the channel base, but Nu plot doesnt give you this result because of the jump of Nu number at the end of channel, so try to decrease the range of the Y-axis of the plot to see what is the real distribution of Nu number.

malay November 5, 2012 12:21

Quote:

Originally Posted by A7A (Post 390006)
The temperature of the channel base is decreasing, so Nu number must be increasing along the channel base, but Nu plot doesnt give you this result because of the jump of Nu number at the end of channel, so try to decrease the range of the Y-axis of the plot to see what is the real distribution of Nu number.

thanks for reply ...
what about Nu no didnt go to 4.32

A7A November 7, 2012 12:19

Have you checked the reference values you are using like length and temperature.

malay November 7, 2012 12:21

Quote:

Originally Posted by A7A (Post 390834)
Have you checked the reference values you are using like length and temperature.

yes i have checked it ...also i try to change it but still no way ..

carlt336 March 7, 2013 01:52

Malay, did you solve your problem with the heat transfer spikes at each end? I am having similar issues. Could it be a problem in the mesh?

malay March 7, 2013 03:06

Quote:

Originally Posted by carlt336 (Post 412173)
Malay, did you solve your problem with the heat transfer spikes at each end? I am having similar issues. Could it be a problem in the mesh?

not yet ... do you have any idea ?

carlt336 March 14, 2013 23:11

Success!
 
Malay,

Do you have a constant temperature value set for your inlet total temperature? If so, this may be a problem. For my inlet conditions, I imported a total temperature profile simulating a thermal boundary layer and this fixed the heat transfer spike at the inlet.

Best of luck!

flotus1 March 15, 2013 03:13

Try to untick the "node values" option for your plot.


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