|
[Sponsors] |
February 26, 2018, 09:04 |
Heat transfer report
|
#1 |
New Member
FrancoisP
Join Date: Feb 2018
Location: Paris, France
Posts: 5
Rep Power: 8 |
Hello everyone,
I am new to this forum and have issues with a simulation which are rather puzzling. Hope you can help me out! Here it is: I have been simulating forced-convection of air in a 10cm-long, 3.5mm-high channel (heat exchanger). The width of the channel is 2.5mm, but the mesh and computation are done on a 2-dimensional cut. The air enters the channel at 1 m/s, temperature is 20°C. The walls have a constant temperature of 13°C. I want to extract the heat exchange coefficient on the top and bottom walls in this situation. When I run a "Heat transfer report" on the top and bottom boundaries of my 2D design, I get 1.41 W. When I run an "average" report of the "heat transfer" over the same surface, I get 8.7e-3 W. I am really surprised the results are different. Based on simple calculations, the second value is in the correct order of magnitude. Does someone know what the "Heat transfer report" actually reports? I suspect there is a trick because I am working in 2D... Thanks in advance ! FrancoisP |
|
February 27, 2018, 08:04 |
|
#2 |
New Member
Marco Riedel
Join Date: Apr 2011
Location: Germany
Posts: 25
Rep Power: 15 |
Hi Francois,
the "heat transfer report" calculates the heat transfer in every face on the boundary and calculates the sum of that values. The "surface average report" of the previous done "heat transfer report" calculates the average of that value. And that is what you want. Best regards Marco |
|
February 27, 2018, 10:22 |
|
#3 |
New Member
FrancoisP
Join Date: Feb 2018
Location: Paris, France
Posts: 5
Rep Power: 8 |
Hello MRI, thanks for your answer !
I tried to report the "sum" of the "boundary heat transfer" over the same surface. As you predicted, I got the same result as the "heat transfer report" : 1.41 W. So, I understand now that the correct value was the average. Out of curiosity, I still don't get what the other value is. The heat transfer report needs a surface. I feed in these pink parts : https://ibb.co/fUDEVx What does the "sum" of the "boundary heat transfer" mean, exactly ? Does it sum the heat transfer over the adjacent surfaces ? What is the application of this feature? Thanks again for your quick answer ! FrancoisP |
|
February 28, 2018, 01:30 |
|
#4 | |
Senior Member
|
Quote:
|
||
February 28, 2018, 10:05 |
|
#5 |
New Member
FrancoisP
Join Date: Feb 2018
Location: Paris, France
Posts: 5
Rep Power: 8 |
Hello Ashokac,
We have the two following reports over the previous 50 mm² surface :
Could you show me where I am wrong ? Thank you ! FrancoisP |
|
February 28, 2018, 10:15 |
|
#6 |
New Member
FrancoisP
Join Date: Feb 2018
Location: Paris, France
Posts: 5
Rep Power: 8 |
||
February 28, 2018, 10:38 |
|
#7 |
New Member
Marco Riedel
Join Date: Apr 2011
Location: Germany
Posts: 25
Rep Power: 15 |
First of all there is something wrong with your area of the boundary. If you calculate in 2D, Star-CCM+ refers to a standard width of 1m, so your area has to be in the range of *.e-3 m^2. And you should keep in mind that your Region consists of top and bottom surface (thats what I understand when I look on your pic), maybe you don't consider it in your simple calculations. For deeper knowledge its always good to look in the user guide under "statistic reports" or on the steve-portal. Special cases are described there very good.
Best regards Marco |
|
February 28, 2018, 11:59 |
|
#8 |
New Member
FrancoisP
Join Date: Feb 2018
Location: Paris, France
Posts: 5
Rep Power: 8 |
Hi again MRI,
Many thanks ! I suspected there was a trick due to the 2-dimensional calculation ! With this standard 1m-width, I get the correct order of magnitude. The top and bottom surfaces were selected on purpose. No problem here. Thanks again! (and I will look up steve portal) FrancoisP |
|
Tags |
heat transfer modelling, reports, star ccm+ |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
UDF for mass and heat source with heat transfer | rajendra1 | Fluent UDF and Scheme Programming | 35 | October 13, 2017 05:04 |
Error finding variable "THERMX" | sunilpatil | CFX | 8 | April 26, 2013 08:00 |
Question about heat transfer simulation | Anna Tian | Main CFD Forum | 0 | January 25, 2013 19:53 |
radiation heat transfer | GeHa | FLUENT | 1 | September 5, 2012 15:56 |
Convective Heat Transfer - Heat Exchanger | Mark | CFX | 6 | November 15, 2004 16:55 |