CFD Online Logo CFD Online URL
Home > Forums > Phoenics

immersol -external radiation source set-up problem

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

LinkBack Thread Tools Display Modes
Old   November 6, 2014, 14:10
Default immersol -external radiation source set-up problem
New Member
Join Date: Nov 2014
Posts: 2
Rep Power: 0
akiaqi is on a distinguished road
hi, I am trying to simulate a case where an XPS slab is receiving solar radiation and losing heat to the external environment (25oC) by radiation and convection and to the room through conduction and convection (25oC). I thought it would be pretty simple but turned out something I need help. The temperature is crazy high (249oC). Both the radiation flux and the convection flux is about 100 W, which is a lot less than my calculation based on the temperature computed.
The solar radiation is set as an internal source of the boundary cells at the edge of the wall. From the result file, the 200 W solar radiation was correctly executed. The boundary source was set as instructed by the Immersol instruction:

The default values and coefficients were then modified
SPEDAT(SET,EXTRN_TEMP,OF IMSW001,R,25) -----modify the external temperature to 25 oC
SPEDAT(SET,EXTRN_CO1 ,OF IMSW001,R,4.536E-08) ---modify A=Sigma*E*Area
SPEDAT(SET,EXTRN_CO2 ,OF IMSW001,R,5) ---modify B=Area*h
SPEDAT(SET,EXTRN_PWR ,OF IMSW001,R,1) ----modify D=1
I was expecting the source would follow Q(W) = 5.67*10-8*ε*Area*(Te^4 – Tw^4) + Area*h*(Te - Tw)
But the output source for T3 is 98 W and for the TEM1 is 98W as well. The wall temperature at the boundary reaches 250 oC. With this value and the above formula, I calculated the radiation would be 760 W and the convection would be 1125 W. Why is that? I think I must have understand the formula and the patch-coval wrong. But t I could not find any other documents on how they are to be used.
BTW, the XPS is an 0.5*0.5*0.5m3 slab, but gridded as a 1-D problem. So the area above is 0.5*0.5m2.

Any help or hint is very much appreciated.
akiaqi is offline   Reply With Quote


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
GPU Linear Solvers for OpenFOAM gocarts OpenFOAM Announcements from Other Sources 36 March 29, 2017 08:05
Swak4Foam funkyDoCalc with OF2.3 massflow NiFl OpenFOAM 11 November 1, 2016 07:43
SparceImage v1.7.x Issue on MAC OS X rcarmi OpenFOAM Installation on Windows, Mac and other Unsupported Platforms 4 August 14, 2014 06:42
OpenFOAM without MPI kokizzu OpenFOAM Installation 4 May 26, 2014 09:17
OpenFOAM on MinGW crosscompiler hosted on Linux allenzhao OpenFOAM Installation 127 January 30, 2009 20:08

All times are GMT -4. The time now is 06:53.