CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Finding heat transfer coefficient "h" at tube bundle surface -help!-

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   April 22, 2013, 04:08
Exclamation Finding heat transfer coefficient "h" at tube bundle surface -help!-
  #1
New Member
 
Burak
Join Date: Apr 2013
Posts: 4
Rep Power: 3
bluejojoba is on a distinguished road
Hello guys!

I am trying to find the "h" coefficient of a tube bundle in a duct. You can see the geometry as attached.

Problem conditions are:
Tubes are at 90C constant.
Fluid is water at 10C with 0,5 m/s inlet.

The steps I followed on FLUENT are:

1- Models: energy equation, k-omega standart & enhanced wall treatment
2- Materials: conditions of water at 10C
3- Cell zone conditions: changed to water as described above
4- Boundary conditions: Inlet 0,5 m/s at 283 K with 1% turbulent intensity and hyraulic dia. of the duct
Outlet is outflow
Tubes are walls at 363 K constant
Duct walls are walls and insulated, thus no heat flux
5- Reference Values: Compute from "inlet"
6- Monitors: Area-weighted average & surface heat transf. coeff. of tubes
7- Solution Initialization: standard initialization compute from "inlet"

After 1000 iterations, I adapt boundary and region twice and run another 1000 iterations, and I get these values:

h = ~7300 w/m2K
Nu = 11242
dT= 2,75K

But if I do a manual calculation according to Zhukauskas' equation for staggered heat exchangers this is what I get: (please see Empirical Calculation.pdf)

h = 11388 w/m2K
Nu= 290,3
dT= 4,5 K

Why I get that different solutions? I am new at CFD and I tried a lot of different ways in FLUENT such as different meshing, different turbulent intensity or models but i still don't get what I should be getting.

Can you please help me where I am doing wrong?

Thank you in advance,
bluejojoba
Attached Images
File Type: jpg HX geometry.jpg (48.3 KB, 15 views)
Attached Files
File Type: pdf Empirical Calculation.pdf (86.6 KB, 19 views)
bluejojoba is offline   Reply With Quote

Old   April 24, 2013, 20:17
Default
  #2
New Member
 
Burak
Join Date: Apr 2013
Posts: 4
Rep Power: 3
bluejojoba is on a distinguished road
anyone guys? I am really desperate.
bluejojoba is offline   Reply With Quote

Reply

Tags
coefficient, forced convection, heat exchanger

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
error message cuteapathy CFX 14 March 20, 2012 07:45
Heat transfer Coefficient san.pirate CFX 8 October 24, 2009 05:49
Concentric tube heat exchanger (Air-Water) Young CFX 5 October 6, 2008 23:17
Heat transfer tube Takeshi CD-adapco 4 July 15, 2003 10:44


All times are GMT -4. The time now is 14:16.