CFD Online Logo CFD Online URL
Home > Forums > STAR-CCM+

Wall y+, heat transfer coefficient

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

LinkBack Thread Tools Display Modes
Old   January 29, 2014, 10:44
Question Wall y+, heat transfer coefficient
Join Date: Oct 2011
Location: Thessaloniki, Greece
Posts: 72
Rep Power: 6
crevoise is on a distinguished road

I am investigation heat transfer from a flow through a pipe with solid. The fluid and the solid are initially at 900K and the flow is at 900K.
I have a mesh for the fluid, and one for the solid (1mm thickness).
The fluid mesh has 5 fine elements next to the solid.
My flow velocity is about 20m/s, and the fluid is air.
I am using k-epsilon model

For the heat transfer of the solid to the environment, I am using 'convection' as thermal specification, with 10 W/m2K for heat transfer coefficients and 300K for ambient temperature.
For the interface fluid/solid, I let the default specification of CCM+

At the end of the computation, I am checking the 'local heat transfer coefficient' at the interface fluid/solid (I have read in the manual that the local definition is used there).
I am getting quite high value for the coefficient (around 220 W/m2K)
When I am checking the local reference temperature, the temperature range between 900 and 840K (frm inlet to outlet of the pipe), corresponding to the last layer of fluid at the vicinity of the solid.

My first question is:
1/ Does the reference temperature should be the one at the vicinity of the solid? I thought this temperature should be the bulk one? (which is then roughly 900K)?

I have then investigated the y+, giving a value of around 5 (taken at the fluid/solid interface).
My second question is thus:
2/ I am wondering if I should coarsen the mesh next to the solid, in order to achieve a larger y+ and get a reference temperature nearer to the bulk one.
Does it sounds ok to someone? (I will investigate it, but I wanted to have some external point of view on that)

3/ Finally, is it possible to force CCM+ to compute the local heat transfer coefficients using the bulk (or mass flow average) temperature?

Thanks a lot for your tips on this mater
Best regards
crevoise is offline   Reply With Quote


heat transfer coefficient, reference temperature, wall y+

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 finding variable "THERMX" sunilpatil CFX 8 April 26, 2013 07:00
Wall Transfer Coefficien - Heat Transfer Coefficient - CFX Gargioni CFX 9 April 15, 2013 07:46
wall heat transfer coefficient elsa CFX 1 March 23, 2010 06:28
Wall heat transfer coefficient (HTC) problem Mohamed khamis CFX 1 January 16, 2010 00:12
CFX wall heat transfer coefficient mactech001 CFX 1 January 5, 2010 22:33

All times are GMT -4. The time now is 00:38.